[crm-sig] Uniqueness of property names in the CRM.

Gill, Tony TG at mellon.org
Tue Oct 15 17:54:00 EEST 2002


Yes, a slightly more concise version of this response would make an
excellent FAQ question.

Cheers,

T.
======================================================================
Tony Gill, ArtSTOR Director of Metadata
The Andrew W. Mellon Foundation, 140 East 62nd Street, NY, 10021, USA
t1 (direct): +1 (646) 274-2265,  t2: +1 (212) 838-8400
w: http://www.mellon.org,  f: +1 (212) 223-2778



> -----Original Message-----
> From: martin [mailto:martin at ics.forth.gr]
> Sent: Wednesday, 09 October, 2002 6:58 AM
> To: crm-sig at ics.forth.gr
> Subject: [crm-sig] Uniqueness of property names in the CRM.
> 
> 
> Dear All,
> 
> I had the following question about the CRM, I think it is a good FAQ.
> Please let me know, if you disagree with my explanations:
> 
>  >I am curious about the lack of uniqueness in the naming of 
> CRM properties.
> 
> 
> 
>  >(1) You have a single ID for each property, covering both 
> directions, eg P9 = consists of (forms part of). In RDD we 
> assign IDs to both directions, as they are semantically distinct.
> 
> 
> This is a philosophical topic. For us, both directions belong 
> to the same, directed
> property. We do not accept models for the scope of the CRM, 
> that use one-way links.
> For us, if there is a link, it can always be read in two 
> directions, normally like
> active and passive voice. We can discuss more about that. Not 
> all models regard both
> directions as semantically different. E.g. UML assigns two 
> names, as we do.
> 
> 
> 
> 
>  >(2) Property names are also not unique (eg "consists of" 
> for P5, P9, P45 and P88).
> 
> 
> The property is unique by the number, not by the name. Names 
> are mnemonics,
> not meant to convey meaning but to remind the meaning. The 
> CRM is intended to
> be international, not English. In a translation, mnemonics 
> are exchanged,
> numbers persist.
> 
> 
> 
> 
> 
>  >There does not seem to be any strict consistency in the 
> definitions of properties with the same name, or of the 
> pairings of names: eg
>  >
>  >    P5    Condition State    consists of (forms part of)    
> Condition State
>  >
>  >    P9    Period                consists of (forms part of) 
>       Period
>  >
>  >    P45  Physical Stuff        consists of (is incorporated 
> in)    Material
>  >
>  >    P46  Physical Stuff        is composed of (forms part 
> of)    Physical Stuff
>  >
>  > so I assume there are no underlying abstract properties or 
> verbs which unite them?
> 
> 
> Underlying abstract properties are given explicitly by 
> "subproperty of" statements,
> and are not linguistically implied. In cases of pure 
> restriction, as the
> "identified by" series, the same name is used deliberately. 
> The mnemonic is always
> chosen to give a better reading in context. P5, P9 and P45 
> never co-occurr, because the
> entities are disjoint.
> 
> The mnemonics work well to replace properties in data by quasi-
> natural language. This is very beneficial to convey the model 
> to non-computer experts.
> We are more interested in how an instance looks like under 
> the CRM schema, than how the
> CRM schema looks like as a total. This is also due to the 
> fact, that the CRM is not designed
> as data entry tool, where users would need to select 
> properties,(and may be confused by
> multiple occurrence of the same name) but for transformation of
> data under local data structures into a common form.
> 
> We deliberately did not assume a common "part-of" theory. 
> There are too many different
> axioms, even for material objects, so that "part-of" seems 
> rather to be on a meta-meta-level.
> Particularly, a common part-of of disjunct concepts would 
> introduce "unintended models".
> Periods, e.g. can't consist of Physical Stuff !
> 
> 
> 
> 
> 
>  >This creates some difficulties in mapping to other schemas, 
> as it means there is no unique single name, for example, for 
> "consists of" as a property linking Physical Stuff and 
> Material. I can see 
>  >that this is manageable when using CRM as a reference 
> model, but I wonder if you have considered the implications 
> for mapping?
> 
> 
> We do have. Map to the identifier. Use the names as 
> representation labels.
> 
> 
> 
>  >I have been doing some test mappings, and I have simply 
> used (for example) "P9a" and "P9b" to distinguish the 
> directions of properties. The non-unique textual names do not 
> then cause an >absolute 
> problem, although it is confusing to have elements with 
> identical headwords.
> 
> 
> If you read our RDFS version, you will see the same. Due to 
> an ugly assymetry
> in RDF use of properties, we are forced to declare forward 
> and backward
> properties as distinct, even though in RDFS they are symmetric.
> 
> We propose: P9F, P9B for those models, that cannot deal with 
> bidirectional
> properties. That allows to recover the common meaning at any 
> useful time.
> 
> 
> 
> 
>  >Have I understood this correctly, or missed something? Can 
> you explain your thinking on this?
> 
> 
> To make the point more clear: If Martin "is son of" Wolfgang, 
> Wolfgang "has son" Martin.
> This is a coimplication. Hence, there are not two independent 
> concepts. Do you
> have other concepts in mind?
> 
> Please let me know, if this makes sense, or if I have missed 
> something.
> 
> ======================================
> 
> BTW, the latest version of the CRM is now available as RDFS. 
> Please test.
> (http://cidoc.ics.forth.gr/docs/xml_to_rdfs/CIDOC_v3.3.2.rdfs).
> It is machine generated, so I hope it is free of spelling errors.
> 
> best,
> 
> Martin
> 
> -- 
> 
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