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 <mar...@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: mar...@ics.forth.gr > Web-site: http://www.ics.forth.gr/isl > > > _______________________________________________ > Crm-sig mailing > listCrm-sig@ics.forth.grhttp://lists.ics.forth.gr/mailman/listinfo/crm-sig > > -- > *Richard Light* > > _______________________________________________ > Crm-sig mailing > listCrm-sig@ics.forth.grhttp://lists.ics.forth.gr/mailman/listinfo/crm-sig > > > -- > ------------------------------------ > 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: mar...@ics.forth.gr > Web-site: http://www.ics.forth.gr/isl > > _______________________________________________ > Crm-sig mailing list > Crm-sig@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>
