Wikidata:Requests for comment/Refining "part of"

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An editor has requested the community to provide input on "Refining "part of"" via the Requests for comment (RFC) process. This is the discussion page regarding the issue.

If you have an opinion regarding this issue, feel free to comment below. Thank you!

Since the property part of (P361) is being used as a placeholder for too many possible meanings, it would be good to discuss its current uses and find better suited properties to cover them.

Possible divisions[edit]

organic part of / organic parts[edit]

Limb, appendages, and other organs present in living beings

  • hand-finger
  • bird-beak
  • apple-apple tree

subsystem of / subsystems[edit]

Group of independent but interrelated elements comprising a unified whole

  • Jupiter-Solar System
  • Africa-Earth

creative work part of / consists of creative works[edit]

Splitted parts of creative works (not to be confused with editions)

  • Polonaise Op. 40 No. 1 - Polonaise Op. 40
  • Allgemeine Deutsche Biographie, 10th volume - Allgemeine Deutsche Biographie

manufactured part of / consists of manufactured parts[edit]

Identifiable parts (divisible or not) found in man-made objects

  • engine-car
  • mug-handle

attribute part of / consists of attributes[edit]

A quality or characteristic inherent in or ascribed to someone or something.

  • living being-behavior
  • orange fruit-orange color
  • addition-Commutative property
  • monarch-Line of hereditary succession
  • Zeus-Lightning bolts

conceptual part of / consists of concepts[edit]

Constructed relation between concepts

  • Punic wars-Third Punic War
  • 1387-1380s
  • monarch-monarchy
  • cosmology-astrophysics


  • The criteria I have followed has been to aim for clarity and usability, while orienting it to known cases that would benefit from this division. I have avoided technical classification systems or strange parthood relationships that are not well-understood or not that frequent.--Micru (talk) 11:51, 14 June 2014 (UTC)
    This is a bad start for a discussion. Nobody will nether know why you made the choice to made if you don't explicit the reasons. Here we have the result of your thinking without a lot of clues about what is going on.
  • A lot of these specialized properties don't really seems conceptually different. For example the organs / organism composition relationship is not very different of manufactured objects composed of other objects. Given the fact that we know the class of items in a claim, for example
    < Panetary system > has part (P527) [SQID] < Planets >
    < Human skull > has part (P527) [SQID] < Human bones >
    we can infer if we actually talking of organs or of manufactured objects. So claim with part of are already pretty informative. Although specializes properties could be useful to express constraints in an easier way.
  • The Composite creative work in more interesting as composition about non physical (sometimes) objects like musics or virtual objects like recording or video games, but I did not really see the problems you actually highlights here. TomT0m (talk) 17:36, 14 June 2014 (UTC)

Comments about attribute part of / consists of attributes[edit]

  • This one seems to be quite generic to me, need to check if this is really needed (or maybe could be more restricted to certain cases?). --Bthfan (talk) 12:06, 14 June 2014 (UTC)

Background research[edit]

part of (P361) is a fundamental property in many ontologies of the Semantic Web. For example, it's used in FRBR to define the relationship between "work", "expression", "manifestation" and "item".

Participants in this discussion should do some background research on part of before making any policy decisions regarding this property. It is important to build on precedent and tie in with conventions. Wikidata does not exist in a vacuum, and the question of how best to deal with part-whole relations is not new. A Taxonomy of Part-Whole Relations by Chaffin and Hermann is a very widely-cited work on this. They define six types of part-whole (i.e., "meronymic") properties:

  • Component/integral object. Examples: handle-cup, punchline-joke
  • Member/collection. Examples: tree-forest, card-deck
  • Portion/mass. Examples: slice-pie, grain-salt
  • Stuff/object. Examples: gin-martini, steel-bike
  • Feature/activity. Examples: paying-shopping, dating-adolescence
  • Place/area. Everglades/Florida, oasis-desert

The paper goes on to describe each of the subproperties of part of in detail. We have a generic property for the "Place/area" subproperty -- location (P276). Readers may realize that we have quite a few analogs of located in; see the request for deletion of the event location property (P766) for perspective.

Another relevant publication on part-whole relations is in a W3C working note -- Simple part-whole relations in OWL Ontologies -- by two prominent researchers in ontology / knowledge representation. I recommend that those interested in this subject search around the web to see how part-whole relations are used in ontologies. It would be best to have our policy be as non-unique to Wikidata as possible. Let's familiarize ourselves and adopt with this subject and adopt conventions from the Semantic Web. Emw (talk) 13:28, 14 June 2014 (UTC)

Emw, precisely because I did background research, I realized that there was no point following standard conventions if we want something usable. Most of the categories that you have posted can be represented with the suggested properties or with some that are existent. The ones that I didn't consider (like portion/mass) are quite useless in our context or they would be better represent with other properties (like "typical ingredients", or "typical materials").
As with other properties, we need to find our own way to represent concepts, if later on we can match them to external ontologies, perfect, and if not, it is not such a big deal.--Micru (talk) 14:02, 14 June 2014 (UTC)
Micru, could you please summarize your background research, perhaps with a few links so others can assess things? Why do you consider standard conventions unusable? (What are those standard conventions? I assume you do not mean those currently in Wikidata -- I am referring to background research outside Wikidata.) I suppose we see things a bit differently. I generally prefer to use conventions from the wider Semantic Web and facilitate interoperability with other vocabularies as much as possible. Emw (talk) 14:20, 14 June 2014 (UTC)
Here there is a good summary of mereology. As said, interoperability shouldn't restrict finding more suitable ways for our community to represent concepts. Remember that "GND type" is also a standard, and it had to be dropped because it was getting on the way.--Micru (talk) 14:31, 14 June 2014 (UTC)
Micru, that Standard Encyclopedia of Philosophy article on mereology is great, but how does it relate to the discussion at hand -- the conventions of representing part-whole (i.e., mereoological) relations in the Semantic Web? I think it would be helpful to look at other major ontologies' use of part of and evaluate why -- or why not -- those practices could work well for Wikidata.
My impression is that we simply need better guidelines on the use of part of, its subproperties, and related properties. For example, don't put claims like "has part (P527) Neptune (Q332)" in universe (Q1). (Such statements are correct but clearly misplaced.) Emw (talk) 15:29, 14 June 2014 (UTC)

Improving 'member of' and 'consists of'[edit]

Two things have bothered me for a while about a couple of properties closely related to part of (P361). First, the domain and range of member of (P463) should be dropped. That property should be a generic subproperty of part of, where the only difference is that member of be non-transitive. Second, since the main purpose of has part (P527) is to be an inverse property of part of, we should change the label of consists of to has part. The is pretty standard practice in ontologies; see GO Ontology Relations and Simple part-whole relations in OWL Ontologies (hasPart). Emw (talk) 13:40, 14 June 2014 (UTC)

We shouldn't be mixing issues, let's address first the "part of" refining and then we can take a look to "member of" - which also needs some depuration.--Micru (talk) 14:06, 14 June 2014 (UTC)

Comments on proposed divisions of 'part of'[edit]

I am somewhat concerned that three of the six proposed divisions of part of are domain-specific: organic part of, creative work part of and manufactured part of. I see no significant benefit from dividing 'part of' quite this way. In particular, with organic part of, this is not how part-whole relations are handled in biological or chemical ontologies. For example, if you look in GO Ontology Relations, you'll see a diagram of the statement "mitochondrion part of cell". And in ChEBI, the reference ontology for biochemistry used in Open Biomedical Ontologies, you'll see that the ChEBI record on hydrogen says "hydrogen molecular entity has part hydrogen atom", not has chemical part or some such.

Dividing part of along such superficial domain-specific lines would come at a significant cost. Needing to learn special ways of simply saying "this is a part of of that" from one domain to the next is a barrier to entry for new users (or experienced users in a new domain). The division also seems a bit arbitrary. If we have organic part of, then why not chemical part of to describe the same relation among chemicals, or geological part of among geological entities, or archaeological part of among archaeological entities? Emw (talk) 14:11, 14 June 2014 (UTC)

They are not "domain specific", they are "attribute specific". Living beings have parts that grow, that evolve, and that in general follow a common pattern. Same for "manufactured objects". True that a creative work can be considered a "manufactured object", but for the sake of clarity I have divided them. A "hydrogen molecular entity" is an inert system composed of subsystems (hydrogen atoms).
To represent domain-specific parthood, a better way would be to use a qualifier "type of part", there you could add further details on how the part relates to the whole. It is not such a bad idea to use qualifiers, since we would need a way to indicate set-completeness or other characteristics of the relationship.--Micru (talk) 14:44, 14 June 2014 (UTC)
By the definition of "domain-specific" as used throughout the Semantic Web, literature on ontology, and discussions on Wikidata like this for well over a year, those properties would typically be called "domain-specific". In addition to terms like "attribute-specific", your use of notions like "subsystem" seems novel. Looking at your examples at top, what makes something like "Jupiter" a subsystem, but "engine" not a subsystem? The Basic Formal Ontology (overview here) provides a useful set of terms for discussing this type of thing, e.g. "independent continuant", "material entity", "object aggregate", etc.
Can you further explain how you think part of is "being used as a placeholder for too many possible meanings"? In a statement like "beak part of bird", surely users are not confusing a beak with a creative work or a manufactured thing like a cup. Similarly, I don't think anyone is mistaking a cup handle as an organic thing.
For reasons like that, I don't think domain-specific parthood is worth representing in a special way with properties like organic part of or part of with a qualifier type of part. Humans can almost always intuit and computers can automatically infer the domain by simply looking at the label, description, or using the item's instance of (P31) or subclass of (P279) claim. Emw (talk) 15:25, 14 June 2014 (UTC)

Proposal for slightly different division and usage guidelines[edit]

I have to agree with Emw here: the proposed division of uses is not natural to me either. I am greatly in favour of dividing things, but the dimensions chosen here do not strike me as very intuitive. Here is what I would suggest:

  • Physical part of. A relationship between two concepts that describe things you can touch: A is a part of B if the atoms of B are a superset of the atoms of A. This subsumes the suggested "organic part of" and "manufactured part of". It also subsumes the example "Africa-Earth" from "subsystem".
  • Process/event part of. A relationship between two concepts that describe events or processes. "Part of" holds if the events that make up one of the concepts are also part of the events that make up the other concept. The example above is "Third Punic War part of Punic wars" and maybe also "1397 part of 1380s".
  • Metaphorical/figurative part of Abstract concepts that do not have a direct manifestation as physical objects or events may still be defined to consist of parts. This is natural when a physical/temporal relation is "almost" there: "Chapter 1 is part of the book" (if you print the book, the pages of Chapter 1 are a physical part of the book), "The first movement of the symphony is part of the symphony" (if you perform the piece, the events associated with the first movement are part of the events of the overall performance). This case covers the examples given under "creative work" above (I don't think that the idea is in any way specific to creative works though, e.g., "adolescence is part of childhood").

In addition, we often have complex concepts that are not a pure example of the above. In a general sense, hardly any human concept can be reduced to the set of its atoms (at least if you are slightly inclined towards idealism: a motorcycle is more than a collection of parts). We can still use "part of" to express a relation between the physical/process/... aspects of a concept even if there are more aspects around.

This is where I would draw the line. All the other examples given above are not "part of" for me. The reason is that they are too abstract to allow for a clear understanding of the relationship that "part of" expresses. Let me illustrate by an example:

  • "1 is part of the real numbers"
  • "The natural numbers are part of the real numbers"

Which one is true? Both? In reality, these two are completely different relationships (element of a set vs. subset of a set). You might say: "Let's just mix them -- no problem using a property in two ways." But the problem is that the two different meanings can occur for the same thing:

  • "The natural numbers are part of the inifinite sets"

It is completely clear to mathematicians that these things must not be confused. However, if you go to less formal disciplines, you can easily make the same confusion there without having a mathematician nearby that explains the error to you:

  • "The Fellowship of the Ring is part of the Lord of the Rings trilogy"
  • "The Fellowship of the Ring is part of 20th century literature"

The second is bogus to me, but it's really hard to tell for people, since "part of" is used so much in common language (only yesterday, I deleted "landscape part of geography"!). In fact, philosophy itself has suffered for most of its history from the recurring confusion of subset of and member of.

To sum up, I would propose the following guidelines for part of:

  • It should only be used between two things of the same kind: two physical objects, two processes, two works of art, two groups of people.
  • It should not be used where more specific properties exist: material used, member of, instance of, subclass of, genre, ...
  • It should never be used for expressing something as vague as "is often associated with" or "typically occurs together with".

In general, "part of" to me seems to be an attempt to reduce the number of properties by merging properties of different meaning into one, simply because they can be called the same in English. Reuse is good, but mixing meanings is not. The many (non-agreeing) definitions of "part of" in semantic technologies and philosophy confirm that this is a likely issue here.

I hope that my proposal can be the basis of a consensus, since it covers a large amount of different types of "part of" relationships, including the majority of the examples given here. I don't want to be extremist -- which would be to say that we need to have distinct properties for every aspect of "part of" -- I just want to draw the line where things become vague or contentious.

Finally, thanks for initiating this important discussion. It is an important step towards a stable and clear use of part of.

Best wishes,

Markus Krötzsch (talk) 18:20, 14 June 2014 (UTC)

I fully agree with this comment. TomT0m (talk) 18:45, 14 June 2014 (UTC)
  • Markus, thanks for your thoughtful comment. I have no objection to reduce the number of divisions if that makes these mereological properties more intuitive.
Regarding the definitions, "physical part of" seems too limited given the context. I would define it as "A relationship between two concepts that describe things related to each other by any of the fundamental forces", that way we could use it for planetary systems, atomic systems, etc. and not just for sets of atoms in direct contact.
Also the label "Metaphorical/figurative part of" could give foot to misunderstandings, what about using a more unambiguous one like "abstract part of"?
All in all it seems that we are reaching some understanding of the properties that convey meaning from different points of view:
  • classing: from the recurrence of similar instances, an idealized class is assumed.
  • parthood/mereological: part-whole relationships for instances or classes
  • sets: relations between collections of objects
  • descriptive: attributes from an object or a class
Given your example of "natural numbers" and the fact that natural number (Q21199) is considered a "subclass of:integer", it suggests to me that we still don't have either the vocabulary nor the perceived need to work with sets, that is why there could be some confusion about how to relate such items. (OTOH, perhaps we would need two separate items: "natural number", the class, and "natural numbers", the set)
Your second example could be easily represented using series (P179) and movement (P135), though I'm not sure "20th century literature" would count as a movement, it seems more like the result of a query...
With descriptive properties there are less problems since most of the existing ones are descriptive (the other major group being nominative). However there are is no way to specify which properties describe a class, that is why I still consider that the "attribute" property might be useful on its own, even if we decide against consider it a parthood property. As Bthfan mentioned above, it might need splitting, any suggestion?
--Micru (talk) 21:04, 14 June 2014 (UTC)
  • I want precedent in how we represent part-whole relations. How do major ontologies handle these things? How are part-whole relations discussed in the literature of knowledge representation and ontology (especially formal ontologies in the Semantic Web)? How can we build on the work of others?
The OBO Relation Ontology has many mereological properties. Many of the properties are specific to biology, but many of them are generic, mereological, and would benefit Wikidata from considered. The OBO Relation Ontology is tied into BFO, which is probably the most widely-used upper ontology. It has part of and a part of subproperty for processes -- i.e. occurs in. (Processes are a type of event; events are "occurants".) Wikidata has a very similar property which is up for deletion -- see Wikidata:Properties_for_deletion#event_location_.28P766.29. I would support changing the label of 'event location' to 'occurs in' (thus not deleting P766) and basing it on BFO semantics for that property.
I am less sold on the worth of an metaphysical part of or abstract part of or otherwise specially metaphysical mereological relationship. Can someone please give an example of a usage of such a property, why instance of (P31) or subclass of (P279) would be inappropriate, and more importantly why part of (P361) would not be appropriate? Can someone provide an example of an external ontology using abstract part of, or some knowledge representation or applied ontology literature on it?
As a side note, this talk of sets is interesting, given that the formal basis for instance of (P31) and subclass of (P279) -- i.e. rdf:type and rdfs:subClassOf -- are the set theory relations ϵ (element of) and ⊆ (subset of), respectively. Precisely speaking they're from description logic, but most of DL derives from set theory and first-order logic. See Interpretation of Axioms and Facts in the OWL Direct Model-Theoretic Semantics specification. Markus, please correct me if I'm wrong. Emw (talk) 23:36, 14 June 2014 (UTC)
  • I oppose the reuse of event location search. Events are part of other events, and they are located in time AND space. I don't see how event location really having a temporal dimension, it relates a temporal event to a physical place. Which does not really meet Marku's criteria of same domain and value type. TomT0m (talk) 10:50, 15 June 2014 (UTC)
@Markus Krötzsch: I like your view on fictional events or abstract part of ! A key point is that fiction or partitions or video games or recording are Virtuality (Q945419) View with Reasonator See with SQID in the sense they are possible experiences, in the same sense a tree seed is a potential furure tree in essence. Every time someone plays a musical album on its computer, some song is a part of the whole actual experience. In the sense the virtual part of is somewhat really close to be the fictional analog of (P1074) [SQID] a part of the experiment of the person who listen in its own world. Really inspiring. TomT0m (talk) 10:58, 15 June 2014 (UTC)

Reply to Emw[edit]

Emw, I have split the answer according to topics, I hope you don't mind.--Micru (talk) 10:33, 15 June 2014 (UTC)

On precedents[edit]

Before I answer to this, let me tell a little joke :) A taxonomist, a mereologist and a Wikidatan walk into a bar. The taxonomist tells the bartender: "After pouring so many gin&tonics in your life I am sure that you have an idealized class of gin-tonic in your mind, put me an instance of it". The puzzled bartender serves him a gin&tonic. Then the merologist tells the bar tender: "in that glass over there put 1/3 part of ice cubes, plus 1/3 part of gin and 1/3 part of tonic". The happier bartender serves him that drink. And then the Wikidatan says: "please, put me any drink but only if the recipe is sourced!"

With that I don't mean that we should get drunk before writing here (other than of understanding and patience :)), just that sometimes it makes no sense to ask for a precedent. None of our properties is sourced because they are community minted concepts that might or might not find equivalents in the "outer world". Even for a field as rich in ontologies as bibliography, we just followed conventions where it made sense and when we could agree. So yes, we can take a look to external ontologies for inspiration, but not as a rule to follow or as a requirement to create properties.

Ha! That may be the first Wikidata joke ever. I'm glad it's a good one, and not some obscure pun about treating classes as instances!
That said, I think it is important to realize that Wikidata does not exist in a vacuum. Many of our properties are sourced from the external world, including part of (P361). This is indicated in their creation discussions, e.g. Wikidata:Property_proposal/Archive/4#P361, or their talk page templates. Same with subclass of (P279): it was first created based on a precedent from CycL, the '#$genls' property. After community discussions like Property_talk:P31#is_a_-.3E_instance_of, its basis was then substituted to be the analog of #$genls in OWL, rdfs:subClassOf. That discussion was all about establishing a foundation for certain "special" properties based on Semantic Web conventions, and I think it has proven to be quite fruitful.
I agree that we should not require properties to be based on external ontologies as a prerequisite for creation. However, reviewing conventions in established vocabularies and the wider Semantic Web should be encouraged. My concern in this particular discussion is that there seems to be much airy ontological opinionating without any real reference to outside literature or complementary footwork to see how part of and other mereological properties are used in actual, applied ontologies outside Wikidata.
part of (P361) is not a garden-variety property like date of birth (P569) or cause of death (P509). It is our most basic mereological membership property. It is sometimes hard to differentiate from other basic membership properties, but it is widely useful, as evidenced by its ubiquity in Semantic Web ontologies. Because of that special status of part of, I think reviewing conventions in the Semantic Web on its semantics, usage and subproperties is something that should be very encouraged.
I will not be able to devote more time to this discussion for the next few weeks. While I would oppose the deletion of part of (P361) and have reservations about some aspects of what's been proposed, I am glad that we are discussing how to improve our practices with part-whole relations. Emw (talk) 16:25, 15 June 2014 (UTC)

On why to split "part of"[edit]

As illustrated above by Markus, linguistically "part of" can have many uses, some of them are aligned with the concept that "part of" represents, but some of them are not. How to signal to users which uses are acceptable and which not? You can manually patrol all edits, or use labels/aliases that hint the restricted uses of the property, or use distinct concepts that allow you to convey better the meaning and perhaps check if the relationship is correct.

Manually patrolling the edits is what we are doing now, and it is not very effective. For instance yesterday I replaced by , not a big deal, but if we had had a way of detecting that outlier, it would have been corrected much faster. Or if the property p1080 wouldn't have been there, then we would have been known that is needed.

My lines of reasoning here are:

  • unclear defined property/label->ambiguous uses->not possible to check for correctness->more difficult to maintain
  • clear defined property/label->unequivocal uses->possible to check for correctness->easier to maintain
Micru, the example mistakes that prompt Markus to "draw the line" are classic confusions between hyponymy (instance of, subclass of) and meronymy (part of). They violate a simple rule: if "A is a B" satisfies the relation between A and B, then "A part of (P361) B" is incorrect.
It is important to distinguish between a statement being incorrect and unideal. Part of statements like "Neptune part of universe" are correct, just not ideally placed. Similarly, your example of "Gordon Freeman part of Half-Life" is also correct, but perhaps too general. Both statements could be phrased better (e.g. "Neptune part of Solar System), but they are correct, i.e. true.
I support using statements like "Gordon Freeman from narrative or fictional universe Half-Life" instead of "Gordon Freeman part of Half-Life". This is not the same as supporting subproperties like abstract part of, physical part of, etc. The former allows us to be more expressive and solves problematic ambiguity; the latter doesn't seem to. Emw (talk) 16:17, 29 June 2014 (UTC)
Emw, you are correct in your appreciation that the statement is not incorrect, just wrongly expressed (or placed), the thing is that we have not just the theoretical problem, we also need a practical solution and a way to explain easily how to use each property. Perhaps we don't need more specific properties, just more specific guidelines, which might be an even bigger challenge. I have left a proposed convention to try to reflect better the differences between these (meta) properties. --Micru (talk) 11:10, 30 June 2014 (UTC)

On "event location"[edit]

Following the guideline of considering parthood just for relationships between items in the same domain, then "even location" wouldn't fall into that category because it mixes two different domains "event" and "location", whereas a parthood relationship should only be between "event-event" or "location-location". That doesn't mean that I don't agree with you about the usefulness of having an "occurs in" property, just that the discussion should "occur in" the right place.

Good point. Looking closer I see that 'occurs in' is not a subproperty of 'part of'. I'll follow up in the deletion request for 'event location' soon. Emw (talk) 16:21, 29 June 2014 (UTC)

On abstract parts[edit]

The most clear example is that between parts of a creative work. There is a sonata with 3 parts, the whole sonata is a creative work, each part is a creative work, the relationship between the parts and the whole is abstract. You can model it with classes, but it will only get confusing and more difficult to maintain (source: I tried).

Why is part of (P361) insufficient to describe parts of a creative work? Why do we need to explicitly declare the parthood relation as abstract? Emw (talk) 16:24, 29 June 2014 (UTC)
It is sufficient to describe it, but not to establish error-control methods. --Micru (talk) 11:10, 30 June 2014 (UTC)

On the nature of classes[edit]

There are two ways of interpreting classes, either you consider them as a model created from observing different instances, or you consider them a human created model from which you derive instances. Which one is correct? It doesn't matter as long as you are aware of the method you are using for interpreting reality (or stated in reality, for that matter). For man-made objects/concepts we could assume that the person modeled first a prototype of, say, Tesla Model S, and then they created instances out of it. But for naturally occurring concepts, like titin, reality has precedence and our class is modeled after observing repeated occurrences of it.

This subtle difference wouldn't matter much if it were not for the fact that we deal with both worlds, the mind-created world of (semantic web, mathematic) ontologies and the mind-created world of inferring reality, and sometimes for the sake of clarity we need to tell them apart, even if, deep in ourselves, we know that both of them are mind constructs.

For that reason I think it is a good idea to use "subclass of" ambiguously to represent both, but when we need to refer to specifically one realm, then we need might need a way to get rid of the ambiguity.

I agree that subclass of should be used to represent both interpretations, to simply ensure that items A and B related with it satisfy the statement "every instance of A is an instance B". I would prefer to keep subclass of neutral in the matter of philosophical ontology you describe, which seems like it might be somewhat of a personal perspective on the nature of classes. Emw (talk) 16:38, 29 June 2014 (UTC)
If by "personal perspective", you mean phenomenological, yes, definitely, but is there any other way to approach subjective matters? From objectivity you cannot model subjective matters. It is necessary to be able to understand from all perspectives what we are doing, because otherwise inconsistencies will start to creep in, and with them the amount of effort necessary to reduce them.--Micru (talk) 11:10, 30 June 2014 (UTC)

Language support[edit]

All this assumes that the languages the Wikidata is supporting are able to support all these "finer" points. This is very unlikely and consequently the result of implementing this will be that in many languages the labels used will be exactly the same. This is very bad and to be avoided.

Given that Wikidata is connected to many external sources, there will be sources among them that do split "is part of" in the suggested way. For those who want to see such finer points, they can use those properties when a mapping has been created between Wikidata and the external source. Thanks, GerardM (talk) 11:21, 17 June 2014 (UTC)

Which finer points do you think are not possible to translate? So far when creating properties no concern has been ever raised about it, only when there was ambiguity which is not the case, why should this one be different?--Micru (talk) 17:38, 18 June 2014 (UTC)

Related topics[edit]

part of (P361) and instance of (P31)/subclass of (P279)[edit]

I think we should include some thinking about the relations beetween classification relations and the part of ones. I is stated in Help:Basic membership properties that the too relations

are both correct uses of part of (P361). This always made be think, now is the time and occasion to discuss this probably :) I'm reluctant to accept that, probably because this make more likely that there could introduce ambiguities about what is a class and what is an instance. Following the token/class distinction, this imply that we have the same relation to say that an individual is a component of another individual, and that a class of individual instances are each probably a part of the instances of another class of individual.

This strikes me especially about virtual objects, such as for example the Snow White story. It can be seen as a class of events in which someone tells this story to a children. Then the part of the story where Snow White eats the Apple has been told many time, for example the premiere of Walt Disney's movie. It happened on this premiere. <The part where Snow White eats the Apple on Walt Disney's premiere> is a part of <Walt Disney's Snow White premiere>, as a token of the experience of the people that were here.

It seems to me that using the same property both for tokens and classes in the sense of the token/class relationship introduce problems an ambiguities, for example in the cases where we use punning and in which a story is both a token of some story or some book and a class of all the tokens where this story has been told ... any thoughts ?

TomT0m, after reflecting about it, I don't see it problematic as long as an instance is "part of" another instance, and a class is "part of" another class. Can we set up that constraint somehow?--Micru (talk) 17:32, 19 June 2014 (UTC)
Yes, I guess we could, it would require to check that if A and B are both classes, and
< A > part of (P361) [SQID] <  B >
, then for every A instance which has a "part of" statement, then the object of the statement is a B instance. Not totally sure that works though.
It seems problematic in the sense that we got a clear rule for instances : every A-instance is allowed to be a part of a B-instance if and only if, roughly, they are both of the same classification : an event can't be part of an object. If we want to reflect that at the class level it may need to reason at the metaclass level : a class A can be a part of a class B if and only if they have some superclass in common which is compatible ? The Class class could work, but it does not seem to be a hard condition to meet. It has a reflection at the metaclass level : a class A can be a part of a class B if they have the same type of class. But all of this needs a little bit of thinking.
By the way I realize it may be not so easy for the part of relationship at the instance level as well. Maybe we should need to list the cases for which there is constraint for an item of some class to be a part of another. We could need a way to state that physical objects can be composited, but physical object cannot be composited with event instances ... TomT0m (talk) 21:11, 29 June 2014 (UTC)
TomT0m, I realized that the only difference between "part of" and "subclass of" is their similarity to the containing set. We want "part of" to have "upper limits" (not too similar, because otherwise it becomes a class) and "lower limits" (not too different, because otherwise becomes irrelevant). Of course those limits are subjective and we'll have to struggle with them. There must be some way to calculate the distance between elements using either "part of", "subclass of", and "instance of", because they all represent that an entity belongs to a set, with different degrees of similarity. If we had a mathematical distance measure, that could help to point to calculate what are the average limits for "part of" and "subclass of" and from there identify outliers. I agree that it needs more thinking.--Micru (talk) 11:31, 30 June 2014 (UTC)
I realized that the only difference between "part of" and "subclass of" is their similarity to the containing set. I don't really understand where your are going.
< my skull > part of (P361) [SQID] < my boby >
does not make <my body> a class at all, it's very different. <my body> and <mu skull> are not sets, they are real world entities. There classes although have a least common superclass, which seems like your upper limit. When we say <skull> part of <body> though we say something different : every skull instance is a part of a body. The composition constraint would impose that those two classes have a least common superclass that can be composed of other objects of the same class. A biological entity, for example, could be composed of other biological entity. Here come another interpretation of the relationship beetween class, I realize : by stating <class A> part of <class B>, we may allow A instances to be part of B instances. Every statement on instances for which it is not true may be reported. TomT0m (talk) 15:41, 30 June 2014 (UTC)
TomT0m, what I meant is that if you start aggregating either "parts of" or "subclasses of", there is a point where the resulting aggregated object can be considered either. <A head> being part of <a body> doesn't make it "a subclass of a body", but if you consider <a head> plus <a torso>, is it enough to consider that group a subclass of <a body>? A subclass has always implicit a "vague similarity", where that is not a condition for parts. Your interpretation is also correct, however it wouldn't help telling apart a class and a part. For that we should introduce "functionality" (wrt the hierarchic system) or "necessariness" (wrt identifying the whole). Perhaps too complicated to be useful.--Micru (talk) 18:26, 30 June 2014 (UTC)
@Micru: This is very vague and do not make sense to me. <a head> plus <a torso> The plus notion is undefined. that group a subclass of <a body> That group is not a class, at first sight it is maybe an example of a body, it is localized it time and space for the Class/token criteria/ If it's a class, then it's the class of all parts of this body. Which is not really useful to know at first sight. I don't understand the rest of your comment. TomT0m (talk) 18:43, 30 June 2014 (UTC)
TomT0m, I will put it in other terms: is a body missing a leg still an instance of the class body? If so, are really all parts of a class necessary or some are more necessary than others?--Micru (talk) 19:03, 30 June 2014 (UTC)
It's a relevant question but I still don't understand how you answer this problem. TomT0m (talk) 19:05, 30 June 2014 (UTC)
Unfortunately I have more questions than answers... could it be that we got closer to know the importance of a part, if we knew the role it plays in the whole?--Micru (talk) 19:22, 30 June 2014 (UTC)
I think this advocates for different properties. I don't know if there is precedents on the semantic web on using part of on classes, Help:BMP do not seem to answer (@Emw: any thought ?). This question makes no sense when an instance is a part of another instance, and this seems to be a source of problems. One answers could be to create properties like instances have parts with some cardinality qualifiers : any number, at least one, beetween one and two, ... Actually this is anwered by using class expressions in OWL languages. But I have not been really successful into pushing this idea atm :)TomT0m (talk) 19:43, 30 June 2014 (UTC)
Or at least some qualifiers for "part of" :) A thing is part of another thing because of something. That is what Markus' proposed subproperties suggest, and also the ones that I originaly proposed. Perhaps we both were being too restrictive.
I also was trying to start introducing class cardinality with "intrinsic properties", but it seems to me that we are ready for that discussion yet.--Micru (talk) 20:18, 30 June 2014 (UTC)

──────────────────────────────────────────────────────────────────────────────────────────────────── In a loose sense, almost all properties can be informally paraphased as "subproperties" of part of (P361) or has part (P527). For example, eye color (P1340) can be considered mereological -- eye color is part of all humans (except for rare cases where one has no eyes). So for example instead of saying Coco Chanel (Q45661) eye color (P1340) dark brown (Q17244894), we could paraphrase this as "Coco Chanel has part dark brown eyes" or perhaps how Marsupium states it in more complex fashion here. This is based on the reading of has part as a liberal has-a property. Of course, just like instance of (P31) can be abused to paraphrase away almost all properties (Coco Chanel instance of dark-brown-eyed person, also explored here), so can part of and has part. Both of these abuses should be avoided.

At the same time, that potential for abuse does not mean instance of (P31) or part of (P361) should be deprecated. Again, part of is a ubiquitous property in Semantic Web ontologies. It is widely used in Gene Ontology and ChEBI, two major biomedical ontologies that serve as unofficial benchmarks of OWL. It is used as a motivating example in new features in OWL 2, e.g. the useful idea of property chain inclusion.

Unlike instance of, which has some special restrictions that prevent subproperties of it from being valid, it does make sense to have certain subproperties of part of. location (P276) is a good example (though it needs refinement): it's rigorously defined in BFO (e.g. here) and used as a motivating example for property chain inclusions in OWL 2. However, this does not automatically imply that subproperties like "physical part of", "abstract part of", etc. are a good idea. While subproperties like located in fulfill a clear need and also, importantly, have precedent in major existing ontologies, I see neither of those criteria met by the subproperties of part of proposed by Micru or Markus.

The discussion of the relation between of subclass of and part of would benefit from being cast in terms of OWL. For example, OWL allows us to form sentences using union, intersection and complement from set theory -- i.e. OR, AND, and NOT Boolean operators. These could function as the "plus" operator that TomT0m refers to. We can also use object property cardinality restrictions to say that a human hand has part human finger with cardinality 5. It's unclear to me how we avoid someone with an amputated ring finger from being said to not have a human hand (and thus not be human). A test case for this is Eric Shinseki (Q373274), who has a partially amputated foot. Being able to make exceptions to rules, like "humans have eye color" or "humans have two feet with five toes each", is important. This requires "non-monotonic" reasoning. Emw (talk) 03:59, 1 July 2014 (UTC)

Emw, thanks for your comments. You forgot to mention that also "subclass of" can be abused, but well, let's not give more bad ideas ;) For cardinality we already have cardinality of the group (P1164), I just used it for hand (Q33767). Non-monotonic logic is more appropriate for capturing deviations than FOL, but still you need to model in which way something can deviate from the norm (class), and which consequences it has. In that regard I noticed in ChEBI that they use "has role", which is exactly what I was thinking about. We only have use (P366), and with that label it seems more appropriate for usable objects than for parts of a system. By having the role, when an instance misses it, you also know in which way the whole is impaired (it will have access to less roles).
Wrt part of I must say that now I'm more inclined to use qualifiers or just properties to clarify part-whole relations. For instance we don't know in which way the part is connected to the whole (gravity? organic tissue?), or if that part can be separated and still keeps its role (integral? proper?). It is also difficult to express which position the part has respect the whole. In BFO this is done with several properties, not just located in, there is also: contained in, adjacent to, etc.
I'm totally in support of boolean operators, but one cannot just let them loose in wikidata and expect that they are used. It will not happen unless they are properly explained and perhaps made easier resorting to common language. For instance a good way to start with this would be to introduce "misses" (equivalent to NOT). A person can miss a foot, a building can miss a window, and that makes it much easier to understand for lay people while keeping OWL compatibility.
Same applies to property chain inclusion, very nice on paper, but until we don't find practical ways to use it and explain it, it is useless.--Micru (talk) 08:20, 1 July 2014 (UTC)
Micru, great comment. Regarding cardinality, if we want to use cardinality of the group (P1164) to indicate exact cardinality beyond the domain of finite group (Q1057968), then we should change its label and domain to be closer to the corresponding property in OWL -- i.e. we should relabel it to "exact cardinality" and remove its domain and range. It would then also make sense to create properties for "max. cardinality" and "min. cardinality".
And regarding use (P366), its label as "use" does not suggest to me that it is "more appropriate for usable objects than for parts of a system". Further, the dichomtomy implied there -- that "usable objects" are disjoint with "parts of a system" -- is not supported by any upper ontologies I'm aware of, including most notably BFO, and doesn't seem especially warranted. Beyond that, though, I do think the property is useful along the lines you suggest. I think it would help to more closely align its label with BFO, i.e. to change "use" to "has role". (While we're at it, we should probably also create an inverse property for it, i.e. "role of".).
I agree that it often helps to clarify part-whole relations, especially in ways that align with existing major ontologies. I would strongly favor doing so with just properties, and not through qualifiers, because qualifiers will not be queryable in the foreseeable future and existing ontologies tend to not use n-ary relations (the purpose of qualifiers). So for example I would support properties like proper part of, contained in and adjacent to, assuming they had the semantics defined in BFO. Relations in biomedical ontologies by Smith et al. provides a good basis. (Despite the paper's title it is relevant well beyond biomedicine.)
Introducing new special concepts like cardinality and Boolean operators would be very useful. Introducing universal quantification and existential quantification, supported in OWL as owl:allValuesFrom and owl:someValuesFrom, would also be very useful. Incorporating these concepts into Wikidata would have effects on the computational complexity of the ontology worth considering, but they would greatly increase how expressive we can be. A major question is how these concepts could be captured on Wikidata: overloading qualifiers to handle them might be a grievous kludge. These things are of course not directly related to refining "part of", but may make sense to consider in a separate RFC while they're fresh in mind. Emw (talk) 11:35, 1 July 2014 (UTC)
I'm not sure I follow you guys. For example located in is really a subproperty of part of ? It might be sometimes, but for example an airplane just stationned somewhere is probably not imho a part of an airport. Class intersection, complements and so on are great, but I'm not sure how it is really related to part of (execpt if you want to state that an a body can have some part like 'arm', where 'arm' is the union of too classes : 'artificial arm' and 'natural arm'. But its related to class definitions, not really part of. I agree that watching the number of exceptions on Property_talk:P225 for example, a non monotonic logic would be cool, but I think we're far from having really explored the full potential of the FOL model. @Emw: On the OWL modeling properties : I think the way we store them is the least important problem, the biggest one is a usability problem. There is no way I really model something like class expressions in Wikidata actually creating statements for each model of the class, this is really tedious compared to using syntaxes like Manchester syntax, for example. Plus we need to make this simple and understandable for users. It's not obvious at all. TomT0m (talk) 18:06, 1 July 2014 (UTC)
TomT0m, when something it is a physical part of a whole, then it is useful to know what is the position of one with respect to the other. It is not about located in being a subproperty or not, it is more about expressing the position of the part wrt the whole, or another significant part of it. And that plus size can really help us to identify misplaced parthood.
When we are entering that a class is part of another, we are also defining expectations (we expect that the class human has a foot) and then we can define something as how it breaks those expectations (Eric Shinseki (Q373274) <misses part> foot). Or that it fulfills them in a different way (x <has part> artificial arm).
Now replying to Emw, I don't think an exact cardinality is what we need, just a "cardinality" which depending on the context it will be considered to be exact, or it will have upper and lower limit. No need for "min" and "max", since the quantity datatype already supports limits. And I am not sure we could do without qualifiers because that would imply having intermediary items (finger group of one hand <cardinality> 5), which would make the editing process too tedious. However, the first step to improve usability should be to simplify the language. Instead of using "cardinality of the group" as a general cardinality property, we can reserve that one for mathematics and have a more generic one called "number of parts" (similar to quantity (P1114)).
There is not going to be range restrictions, the closest we have is the constraints templates and perhaps it will be hard to translate all of them into statements (at least not the exceptions, too many). Besides there is the new suggester, which apparently will work with values too. That can be more effective.
Whatever new property we propose it should be in the terms of what users understand/expect. I'm thinking that "has role" can be confused with "movie role", so we should aim for something more neutral like "has function"/"function of".--Micru (talk) 09:20, 2 July 2014 (UTC)

'part of' and related properties in the Basic Formal Ontology[edit]

TomT0m, you're right about located in: it is not a subproperty of part of. Unlike Micru, I think this is significant. Let's consider the formal instance-level definitions of those two properties in Relations in Biomedical Ontologies. The paper lays the foundation for the usage of part of, located in, and other basic properties throughout all domain ontologies rooted in the Basic Formal Ontology (BFO, outlined here), including Chemical Entities of Biological Interest (ChEBI), Gene Ontology (GO), the Petrochemical Ontology, the Emotion Ontology, and many others.

c part_of c1 at t - a primitive relation between two continuant instances and a time at which the one is part of the other
p part_of p1, r part_of r1 - a primitive relation of parthood, holding independently of time, either between process instances (one a subprocess of the other), or between spatial regions (one a subregion of the other)
c located_in r at t - a primitive relation between a continuant instance, a spatial region which it occupies, and a time

For clarity, let's examine precisely what is meant by "continuant", "process" and "spatial region":

The terms 'continuant' and 'process' are generalizations of GO's 'cellular component' and 'biological process' but applied to entities at all levels of granularity, from molecule to whole organism. Continuants are those entities which endure, or continue to exist, through time while undergoing different sorts of changes, including changes of place. Processes are entities that unfold themselves in successive temporal phases [16]. The terms 'continuant' and 'process' thus correspond to what, in the literature of philosophical ontology, are known respectively as 'things' (objects, endurants) and 'occurrents' (activities, events, perdurants) respectively. A continuant is what changes; a process is the change itself. The continuant classes relevant to biological ontologies include molecule, cell, membrane, organ; the process classes include ion transport, cell division, fat body development, breathing.
Note that continuants and processes form non-overlapping categories. This means in particular that no subtype or parthood relations cross the continuant-process divide. The tripartite structure of the GO recognizes this categorical exclusivity and extends it to functions also.
Continuants can be material (a mitochondrion, a cell, a membrane), or immaterial (a cavity, a conduit, an orifice), and this, too, is an exclusive divide. Immaterial continuants have much in common with spatial regions [18]. They are distinguished therefrom, however, in that they are parts of organisms, which means that, like material continuants, they move from one spatial region to another with the movements of their hosts.
The three-dimensional continuants that are our primary focus here typically have a top and a bottom, an anterior and a posterior, an interior and an exterior. Processes, in contrast, have a beginning, a middle and an end. Processes, but not continuants, can thus be partitioned along the time axis, so that, for example, your youth and your adulthood are temporal parts of that biological process which is your life.
As child and adult are continuants, so youth and adulthood are processes. We are thus clearly dealing here with two complementary - space-focused and time-focused - views of the same underlying subject matter, with determinate logical and ontological connections between them [16]. The framework advanced below allows us to capture these connections by incorporating reference to spatial regions and to temporal instants, both of which can be thought of as special kinds of instances.
We shall also need to distinguish two kinds of instance-level relations: those (applying to continuants) whose representations must involve a temporal index, and those (applying to processes) which do not. Note that the drawing of this distinction is still perfectly consistent with the fact that processes themselves occur in time, and that processes may be built out of successive subprocesses instantiating distinct classes.

In addition to instance-level relations defined above, the paper goes on to describe class-level relations for each basic property. Here is its eludication of part of, which corresponds with some key things we've established in this RFC:

Parthood as a relation between instances. The primitive instance-level relation p part_of p1 is illustrated in assertions such as: this instance of rhodopsin mediated phototransduction part_of this instance of visual perception.
This relation satisfies at least the following standard axioms of mereology: reflexivity (for all p, p part_of p); anti-symmetry (for all p, p1, if p part_of p1 and p1 part_of p then p and p1 are identical); and transitivity (for all p, p1, p2, if p part_of p1 and p1 part_of p2, then p part_of p2). Analogous axioms hold also for parthood as a relation between spatial regions.
For parthood as a relation between continuants, these axioms need to be modified to take account of the incorporation of a temporal argument. Thus for example the axiom of transitivity for continuants will assert that if c part_of c1 at t and c1 part_of c2 at t, then also c part_of c2 at t.
Parthood as a relation between classes. To define part_of as a relation between classes we again need to distinguish the two cases of continuants and processes, even though the explicit reference to instants of time now falls away. For continuants, we have C part_of C1 if and only if any instance of C at any time is an instance-level part of some instance of C1 at that time, as for example in: cell nucleus part_ of cell.
C part_of C1 = [definition] for all c, t, if Cct then there is some c1 such that C1c1t and c part_of c1 at t.
Note the 'all-some' structure of this definition, a structure which will recur in almost all the relations treated here.
C part_of C1 defines a relational property of permanent parthood for Cs. It tells us that Cs, whenever they exist, exist as parts of C1s. We can also define in the obvious way C temporary_part_of C1 (every C exists at some time in its existence as part of some C1) and also C initial_part_of C1 (every C is such that it begins to exist as part of some instance of C1).
For processes, we have by analogy, P part_of P1 if and only if any instance of P is an instance-level part of some instance of P1, as for example in: M phase part_of cell cycle or neuroblast cell fate determination part_of neurogenesis. Formally:
P part_of P1 = [definition] for all p, if Pp then there is some p1 such that: P1p1 and p part_of p1.
An assertion to the effect that P part_of P1 thus tells us that Ps in general are in every case such as to exist as parts of P1s. P1s themselves, however, may exist without having Ps as parts (consider: menopause part_of aging).
Note that part_of is in fact two relations, one linking classes of continuants, the other linking classes of processes. While both of the mentioned relations are transitive, this does not mean that part_of relations could be inferred which would cross the continuant-process divide.

Returning to the topic at hand, we see that part of is used in these ontologies to link both "physical" and "abstract" things with the same property, without a special qualifier to indicate whether its subject and object are physical or abstract.

The elucidation above also supports and refines some constraints on part of we have been vaguely approaching. We have discussed items linked by part of should "have some superclass in common". However, as TomT0m notes in the preceding section, part of should not be used to link "objects" and "events". In BFO parlance, "objects" are "continuants" and "events" are "occurents".

For interoperability with major existing ontologies and firm philosophical grounding, I think it would be best to refine part of along the lines used in BFO. Emw (talk) 12:39, 2 July 2014 (UTC)

Emw, I don't think anyone here suggested mixing parthood of objects with events, quite the opposite (or if someone did I cannot find it). The text you copied is more or less what we have been discussing here, just in more formal terms. Nevertheless I enjoyed reading that paper because it helps identify some basic properties that we are missing:
  • has participant (similar: p710), has agent
  • contained in, adjacent to (subproperties: p197, p47)
  • transformation of, derives from (similar: p144)
Their parthood definition doesn't address "abstract parts of abstract wholes", but it doesn't matter, the "superclass in common" requirement still applies.
This sentence: An assertion to the effect that P part_of P1 thus tells us that Ps in general are in every case such as to exist as parts of P1s. P1s themselves, however, may exist without having Ps as parts, reaffirms my impression that we need a property to indicate when an instance is missing a part, because it is assumed that it has all of them unless indicated otherwise.--Micru (talk) 14:16, 2 July 2014 (UTC)
Micru, BFO's parthood definition accounts for "abstract parts of abstract wholes" by simply using part of between two classes. For example, in the statement "cell_nucleus part_of cell" in the paper, both 'cell nucleus' and 'cell' are abstract: they are universals (classes), not particulars (instances).
Same with "big left toe part of left foot": 'big left toe' and 'left foot' are abstract things. They are subclasses of material entity, but do not refer to a particular material entity, i.e. physical thing. Contrast that with "Eric Shinseki's big left toe part of Eric Shinseki's left foot", which is how BFO and those major ontologies would capture the proposed "physical part of" property. 'Eric Shinseki's big left toe' would be an instance of 'toe', but it would be an unconventional separation of concerns to state whether his big toe is a class or instance in the part of (P361) property when we already have a way to state that with instance of (P31) and subclass of (P279).
While BFO does not use subproperties of part of to indicate a subject's abstract-physical (class-instance, type-token) nature, it does use them to indicate its upper classification. These can be seen by opening in Protege.
Regarding how to state that something is not part of something, I am inclined to prefer a more generic property than "misses part" (which I'd label "does not have part" if I were to support it). Instead of a property-specific negation, as a first approach I would prefer a generic not property, to be used as a qualifier on any statement in need of simple negation. This would function as a way to capture OWL's owl:complementOf, owl:datatypeComplementOf, owl:NegativePropertyAssertion and NegativeDataPropertyAssertion in one Wikidata property: not. More on negation in OWL is here: The advanced negations there would likely require some way to enter complex statements (e.g. in Manchester syntax) on an item's Talk page, but the simple negations there could probably be achieved through the current UI. Emw (talk) 12:49, 3 July 2014 (UTC)
Emw, the examples you give, even being abstract classes, have a physical counterpart. I was referring to purely abstract relationships like "monarch (the office) <part of> monarchy" or "algebra <part of> mathematics". Are they considered processes too?
Before suggesting the property "not", please think about which use cases you might have, because I think there are not that many. Consider also what is the difference between the possible use cases and the rank "no value" option. The "does not have part" property has a clear focus and use, whereas the "not" poses some usability problems.
Remember also that in Wikidata we never make assertions, we just collect claims, which is a significantly different principle.--Micru (talk) 13:20, 3 July 2014 (UTC)
Mircu, thanks for those examples of what you envision abstract part of applying to. In BFO, 'monarch' would be a role. See the 'Role' section on page 3 of Function, Role, and Disposition in Basic Formal by Robert Arp and Barry Smith for a fuller explanation. Going back to a previous critique of yours against a putative property labeled "has role", I would note that similar niche concerns have been raised about subclass of (P279) -- e.g. that it would confuse biological taxonomists because "subclass" is a taxonomic rank, and thus should be avoided in biological taxonomy.
I find both arguments uncompelling and detrimental to interoperability. With subclass of, it makes a large portion of our ontology inconsistent with the rest because of concerns that existing reference ontologies of biological taxonomy have moved beyond. With has role, it prevents us from aligning a separate has function property as used by major BFO ontologies like ChEBI.
Regarding a not qualifier, it would be different from the built-in "no value" option by enabling specific values to be negated. Not would be used to enable simple negation for all statements. For example, it would subsume does not have part. It could also be used to negate more specific statements, e.g. "vegetarian diet not meat", ""shipwreck use (P366) not sailing", "Barack Obama place of birth (P19) not Kenya", "autism has cause (P828) not MMR vaccine", etc. The latter two are subtly but importantly different than deprecated rank in that deprecated statements would have erroneous references per the documentation, while negated statements would have reliable sources making the claim.
Finally, regarding your point about assertions vs. claims: citation needed. The distinction you note seems derive from your personal definition of those terms. Wikidata claims, which when combined with references comprise a statement, are exactly synonymous with assertions, at least in the sense of knowledge representation, which is the relevant context here. Emw (talk) 03:57, 7 July 2014 (UTC)
Emw, and what about "algebra <part of> mathematics"? Should we address it with another property?
It is not detrimental to have more specific properties than other sites. For instance, our parent taxon (P171) can be mapped to an external "subclass of", either directly or indicating that "parent taxon" <subproperty of> "subclass of". The label of the property is not as important as its use, and you have to bear in mind that whatever property is going to be used by people. It doesn't matter much if the name is the same or different as long as it makes the property easier to understand and to use. Just propose the property, and if there are concerns then anyone can propose an alternative label.
I understand your point about the "not", it might have some application. I just hope it will be a bit more used than excluding (P1011).
Assertions vs. claims: theoretically we don't produce any knowledge representation, we aggregate them, that means that we could collect from different sources any assertion that is conflicting with any existing one. Even with you equating statements and assertions, I don't see any point to call "assertion" to something that is not "asserted" (i.e. declared true and the effects of this spread through the system). Claims, of course, become assertions as soon as you integrate them into a reasoning system and you declare them true in a given context, which implies bringing coherence (subjectivity) to the data. This distinction doesn't derive from any personal definition, but from applying a phenomenological approach, which is better suited to the diversity that Wikidata aims to represent.--Micru (talk) 12:40, 7 July 2014 (UTC)

Crossing the continuant-process divide[edit]

According to the paper "Relations in Biomedical Ontologies" posted above by Emw, continuants and processes form non-overlapping categories. This means in particular that no subtype or parthood relations cross the continuant-process divide. That is a great limit for parthood, but still, there are concepts that do not cross the divide, but combine it. For instance, it could be said that human (Q5) combines human behaviour (Q3769299) and human body (Q23852) (cf. category combines topics (P971)). No idea if there is a way in to express this in BFO terms.

That could be represented with a new property, but what happens when this "combined" class is instanced? It can get confusing. Analyzing the concept of book (Q571), it can be seen as a combination of a physical support (continuant) and the information it contains (process?). When it is instanced it could be understood as:

  1. the new item represents only the immaterial part (information)
  2. the new item represents only the material part (ink on paper)
  3. the new item represents an instance of both the "creative work" and of "bundle of pages" (single book)
  4. the new item represents an instance/class of a "creative work" and a class of "bundle of pages" (book edition)
  5. the new item represents an instance/class of a "creative work" and a class of "bundle of pages" (class of all editions)

All these possibilities have confused me in the past because they combine two domains, and sometimes at different abstraction levels (class and instance). It is clear that when we add a part to any of these combinations, we are acting on both domains. A chapter is both a physical entity (pages) and the information contained within, that is why it can be part of a book. It is unlikely that one item that combines domains could appear as only one of them in real life (cases 1 and 2 above), although they can exist in the theoretical domain.

With all this I want to point out that besides parts of continuants and parts of processes, there is a third case when both happen in combination. In those cases, the part must also represent a combination of both, and if it is not it can be assumed that only affects one of the domains the item is a combination of.--Micru (talk) 11:02, 4 July 2014 (UTC)

Hehe, soon you'll ask yourself if life is a process :). I think physical entities are involded in processes. Arguably for example, if the life of Karl Marx is a process, let's call this a biography, then Karl Marx's body is involved in it. I think this is not a case of obvious whole/part relationship : is Karl Marx a whole with parts <Karl Marx body> and <Karl Marx Biography> ? I don't think so. There is a really tight relationship beetween them, arguably they are several viewpoints on the same object. TomT0m (talk) 16:05, 4 July 2014 (UTC)
TomT0m, I don't think either that <Karl Marx body> and <Karl Marx Biography> have a parthood relationship to <Karl Marx>, there is a deeper connection. It can be said that both <Karl Marx body> and <Karl Marx Biography> are a facet of (P1269) <Karl Marx>, however that property misses the point that the one cannot exist without the other, and that they are totally integrated without possibility of separation. According to formal ontologies one could say that <Karl Marx Biography> "has participant" <Karl Marx body>, and perhaps <Karl Marx body> "has agent" <Karl Marx Biography>, but again, that seems a convoluted way to express their shared existence and it doesn't convey the "for A and B to exist, both A and B *have* to happen co-dependently to each other". It would be great to hear Emw's opinion on this, maybe he has seen this already solved in any of the web ontologies he is so fond of :)
A process unfolds itself in successive temporal phases while the necessary conditions exist. Life unfolds itself in successive temporal phases while the necessary conditions exist. A better question to ask onself could be why shouldn't life be considered a process ;)--Micru (talk) 17:29, 4 July 2014 (UTC)

Part Of in FRBR, CIDOC CRM, Taxonomies[edit]

This is a great and very necessary discussion. I'll make a couple very brief comments since I'm on a deadline, and hope to return to it 1 Feb.

  • "Part of" is strongly related to "instance of" and "subclass of", at least because people often confuse them. The same distinction has appeared in Taxonomies/Thesauri. w:en:ISO 25964, the latest standard on Thesauri, distinguishes 3 kinds of "broader" relations: broaderGeneric (similar to "subclass of"), broaderPartitive ("part of"), broaderInsantial ("instance of"). Unfortunately in the current OWL rendition ( all these are subproperties of skos:broader thus mixed together in skos:broaderTransitive. See presentation On Compositionality of ISO 25964 Hierarchical Relations (BTG, BTP, BTI) and a draft paper for counter-examples and a proposal which sub-kind is composable with which other ones.
  • Philosophy has been dealing with these topics for centuries, in disciplines such as ontology (but not the simplified kind in Semantic Web) and mereology. To discount philosophical achievements means to lapse into ad-hoc and brittle structures that won't work.
  • Since Wikidata wants to structure all knowledge, we're hitting all kinds of exceptions and corner cases. In other words, the "thought experiments" of philosophers and ontologists are now finding a large and real experimental ground.
  • To design good approaches, we need to be both aware of (or even experts in) the fundamental philosophical achievements, and temper with practical considerations (eg whether a common editor will understand and apply consistently whatever guidelines come out of these discussions).
    • Understanding the different natures (or sub-kinds of) "part of" relations is essential, since that affects transitivity. You can't always compose different sub-kinds. This is a major subject of study in mereology.
    • I hope not all of us would have to read philosophical treatises (eg the excellent article "Mereology" in The Stanford Encyclopedia of Philosophy) but at least we need to be aware of some examples and counter-examples.
  • CIDOC CRM (ISO 21127, w:en:CIDOC Conceptual Reference Model) is a fundamental ontology that deals with creative works, the process of creation (eg a painter Creating an image in his mind, then Producing a painting, which can then be re-Produced numerous times), lifecycle (eg Production, Modification, Destruction), historic events, etc. You can see the class hierarchy (and graphical illustrations of structures for typical usages) eg at Simpler than BFO in its top-level structure, it has these fundamental distinctions:
    • Endurants (continuants) vs Perdurants (occurrents). In CRM, perdurants form a hierarchy: from historic/cultural Periods, to Events (natural or man-made) to Activities (made by a particular Actor).
    • Conceptual (eg the image of Mona Lisa) vs Physical (eg the original painting in the Louvre or a reproduction): a further split of endurants
    • CRM has specific "part of" relations for many types: physical object (eg "page 3 of Abraham Lincoln's copy of the bible"), conceptual object (eg Sonata part 1 < Sonata), Period/event, Actor (eg person<subgroup<group)
  • In Wikidata too often confusion arises between a design for something and a physical copy made from that design; and which should be an instance. Some have proposed to treat a book (eg Catcher in the Rye) as a subclass of Book, namely the set of all physical copies of Catcher in the Rye. This is totally twisted and won't work.
  • FRBR has dealt with these issues, with the 4 levels Work, Expression (eg a particular translation), Manifestation (eg an edition, something with an ISBN), Item (physical copy); the first 3 are conceptual entities and only the last one is physical. FRBR uses specific relations to cross these levels. I believe that to use the generic relations will cause confusion.
    • Note that I'm not advocating to have all these 4 levels (eg BibFrame has only 3). But we should be aware of the distinctions made by library catalogues, respect them, and generalize the same model for other domains (eg a rocket design vs a physical rocket of that design)
  • Sometimes "part of" relations between parts of a design or conceptual entity beget parallel "part of" relations in physical entities. Eg "pedestals conceptual-part-of statues" begets "pedestal of the Statue of Liberty physical-part-of Statue of Liberty". But these need to be considered and "controlled" individually and carefully, to avoid confusion.

--Vladimir Alexiev (talk) 08:08, 12 January 2015 (UTC)