[Crm-sig] Using multiple instantiation

Martin Doerr martin at ics.forth.gr
Thu Dec 6 19:37:51 EET 2018


Right. It is very dense. I tried to justify multiple instantiation in 
the same text and give practical advice. I am not sure who finds it an 
issue. In the principles of the CRM we describe it again, but may be 
here it would be useful just to make people aware of it, and make an 
example in the Annex. Or omit allover.

Opinions?

Martin

On 12/6/2018 12:55 AM, van Leusen, P.M. wrote:
> Hi Martin,
> Not sure if you would regard me as a typical reader, but I find this 
> text very hard to read and understand without having at least one good 
> worked example to guide me through it. It presupposes so much 
> specialised knowledge about the various types of data management and 
> knowledge organisation systems that, in its current state, only a 
> small group of specialists might find it useful...
> Martijn
>
> On Wed, Dec 5, 2018 at 11:13 PM Martin Doerr <martin at ics.forth.gr 
> <mailto:martin at ics.forth.gr>> wrote:
>
>     This was a proposal by Robert :-). It may be useful for
>     implementers not used to semantic technologies.
>
>     What do other people think?
>
>     On 12/5/2018 6:54 PM, Richard Light wrote:
>>
>>     Martin,
>>
>>     Please explain why you think that this text is needed in the RDF
>>     implementation guidelines. To me, it seems quite generic, and
>>     doesn't offer specific guidance as to what implementors should do
>>     about the issue that their existing systems may be incapable of
>>     expressing certain RDF features. I think it would actually
>>     detract from the usefulness of the document, because it would
>>     confuse and puzzle the typical reader.  [Maybe we need to stop
>>     and think about who the 'typical reader' would be, and what they
>>     would want from this document.]
>>
>>     Richard
>>
>>     On 05/12/2018 16:05, Martin Doerr wrote:
>>>
>>>     Dear All,
>>>
>>>     I propose this paragraph to be added to the implementation
>>>     guidelines for RDFS:
>>>
>>>     "*About implementing multiple Instantiation*
>>>
>>>     Knowledge representation models and more generally semantic
>>>     networks differ fundamentally in one aspect from data
>>>     structures, such as XML, Relational database schemata and data
>>>     structures in all programming languages, including the
>>>     object-oriented one:
>>>
>>>     ·Knowledge representation starts with an item in the real world
>>>     regardless its nature, assigns an identifier to it in order to
>>>     be able to make assertions about it, and then accumulates
>>>     statements (assertions, propositions) about it.
>>>
>>>     ·Data structures start with a set of templates, a set of
>>>     foreseen kinds of statements dedicated to a particular category
>>>     each (class, entity), to be filled in by a user.
>>>
>>>     Consequently, knowledge representation may assign multiple
>>>     classes to a given identifier without any problem. The
>>>     associated processing software will then allow for asserting for
>>>     this identifier all properties applicable to each assigned
>>>     class. This process is called “multiple instantiation. For
>>>     instance, the “weapon” with all its characteristics may also be
>>>     a “ceremonial object”.
>>>
>>>     A system based on data structures must create a different
>>>     instance of the respective templates for each class an item
>>>     belongs to. It may later the link the different instances
>>>     describing aspects of the same thing, in order to simulate the
>>>     mechanism. In particular the very successful “encapsulation
>>>     principle” of object-oriented programming languages requires
>>>     dedicated data structures and constitutes a fundamental mismatch
>>>     with the Open-World modeling of semantic relationships (see, for
>>>     instance Schnase 1993). Fundamental to semantic data integration
>>>     are also superproperties, which are not provided by data
>>>     structures either.
>>>
>>>     The CRM as ontology relies heavily on multiple instantiation:
>>>     Classes that use to co-occur on things simultaneously
>>>     “incidentally”, without being associated with properties only
>>>     applicable to the combination of such classes, are not modelled
>>>     individually as subclasses of multiple parent classes. The
>>>     latter would be called “multiple IsA”. To avoid multiple IsA in
>>>     such cases is an important normalization principle to keep the
>>>     ontology very compact and unambiguous.
>>>
>>>     Most implementations on top of RDF still use RDF as if it were a
>>>     fixed schema and repeat in the UI code all the schema.
>>>     Therefore, the promise of RDF and other semantic models to be
>>>     able to accommodate dynamically new properties often does not
>>>     work. It is still as if they were using Relational systems.
>>>     Generic XML editors do adapt already to the schema, but usually
>>>     the rendering paradigms they employ, without additional
>>>     parameters, are too poor for good UI code. One can however write
>>>     code that reads the RDF schema used at run-time and that extends
>>>     data entry and display by the actual properties found. This
>>>     functionality is foreseen by SPARQL, but most programmers still
>>>     do not appreciate the utility of querying the schema. Even if
>>>     fixed templates are used, the data entry system should foresee
>>>     the same thing to be described by multiple templates, relatively
>>>     freely selectable by the user.
>>>
>>>     In the specification modules of mapping software used to
>>>     transform data into a CRM-compatible form, care must be taken to
>>>     foresee and allow the user to combine RDF classes
>>>     systematically. It may be useful to develop tools for specific
>>>     guidance that show users how a valid path from a given domain
>>>     class to a certain range class can be created by using multiple
>>>     instantiation (and, by the way, also by using subclasses of the
>>>     domain class), such as combining /E41 Appellation/ with /E33
>>>     Linguistic Object/ in order to reach /E56 Language/ via /P72 has
>>>     language./
>>>
>>>     In a local system, another workaround for multiple instantiation
>>>     can be the creation of classes that replace all candidate cases
>>>     for multiple instantiation by subclasses using multiple IsA. For
>>>     good reasons, the compatibility with the CRM is defined at the
>>>     import/export/query level and not at the system internals.
>>>     Therefore, such internal workarounds do not affect the
>>>     interoperability: Whereas the query compatibility of this
>>>     solution with the standard is immediate, the respective
>>>     import/export system simply needs to make the trivial
>>>     replacements of the respective class combinations with their
>>>     multiple IsA counterparts and vice-versa.
>>>
>>>     So, partially, problems with multiple instantiation are a
>>>     question of programming practice. On the other side, it is also
>>>     a question of user training and extended good practice. Users
>>>     may provide feedback about frequent cases where multiple
>>>     instantiation is used, in order to guide users to these
>>>     modelling cases. These could systematically be entered into the
>>>     CRM RDF implementation, without requiring the CRM standard
>>>     itself to repeat them."
>>>
>>>     John L. Schnase, (1993). "Semantic Data Modelling of Hypermedia
>>>     Associations", in: ACM Transactions on Information Systems,
>>>     Vol.11,No.1, January 1993, p 45.
>>>
>>>     Comments welcome!
>>>
>>>     Best,
>>>
>>>
>>>     Martin
>>>
>>>     -- 
>>>     ------------------------------------
>>>       Dr. Martin Doerr
>>>                    
>>>       Honorary Head of the
>>>       Center for Cultural Informatics
>>>       
>>>       Information Systems Laboratory
>>>       Institute of Computer Science
>>>       Foundation for Research and Technology - Hellas (FORTH)
>>>                        
>>>       N.Plastira 100, Vassilika Vouton,
>>>       GR70013 Heraklion,Crete,Greece
>>>       
>>>       Vox:+30(2810)391625
>>>       Email:martin at ics.forth.gr  <mailto:martin at ics.forth.gr>   
>>>       Web-site:http://www.ics.forth.gr/isl  
>>>
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>>     -- 
>>     *Richard Light*
>>
>>     _______________________________________________
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>
>
>     -- 
>     ------------------------------------
>       Dr. Martin Doerr
>                    
>       Honorary Head of the
>       Center for Cultural Informatics
>       
>       Information Systems Laboratory
>       Institute of Computer Science
>       Foundation for Research and Technology - Hellas (FORTH)
>                        
>       N.Plastira 100, Vassilika Vouton,
>       GR70013 Heraklion,Crete,Greece
>       
>       Vox:+30(2810)391625
>       Email:martin at ics.forth.gr  <mailto:martin at ics.forth.gr>   
>       Web-site:http://www.ics.forth.gr/isl  
>
>     _______________________________________________
>     Crm-sig mailing list
>     Crm-sig at ics.forth.gr <mailto:Crm-sig at ics.forth.gr>
>     http://lists.ics.forth.gr/mailman/listinfo/crm-sig
>
>
>
> -- 
> Dr. Martijn van Leusen
> Associate professor, Landscape Archaeology, Groningen Institute of 
> Archaeology
> Poststraat 6, 9712ER Groningen (Netherlands) / phone +31 50 3636717
> Chair, Examination Board for Arts, Culture and Archaeology / Chair, 
> Faculty of Arts Advisory Board for Data Management policies
> Academia page <https://rug.academia.edu/MartijnvanLeusen>


-- 
------------------------------------
  Dr. Martin Doerr
               
  Honorary Head of the
  Center for Cultural Informatics
  
  Information Systems Laboratory
  Institute of Computer Science
  Foundation for Research and Technology - Hellas (FORTH)
                   
  N.Plastira 100, Vassilika Vouton,
  GR70013 Heraklion,Crete,Greece
  
  Vox:+30(2810)391625
  Email: martin at ics.forth.gr
  Web-site: http://www.ics.forth.gr/isl

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