Re: Approaches to Expanding the Semantics of a Community's Sel
Hi Roger Another approach - actually being used - is to create abstract structures describing all the known concrete types used for the same purposes by a superset of communities. Each community then somehow relates (maps) their semantics to the abstract structures and documents this using,say, models or schemas rather than (as in your first example) in the instances. The existing implementations of this concept I'm thinking of are those of CEFACT used for 'haromising' various EDI and XML business standards - namely CCTS (ISO 15000-5). It requires that each vocabulary be sent to a harmonization body by the respective standards body (and takes ages :-). However, a similar idea might be to use RDF in a similar way I guess. Some developments along these lines are appearing which look very interesting but I'm not all that familiar with how folk are using semantics and ontologies in this way. Mention of FOAF looks very interesting. (A variation is for the common provision of techniques which, when used by each standard's body for their vocabulary, facilitate the alignment without, perhaps, the need for the central harmonization.) What these methods mostly have in common as distinct from those you mention is the provision by a separate body of a common abstract or semantic ontology or the like to which each standard can be mapped but whether the mapping need be included in the actual instances (attributes might be already set in stone, say) or whether something like CCTS or RDF (perhaps with SPARQL) are adequate at the schema, model and/or metadata level seems a crucial consideration. Also to consider is to what extent there is a dependency on a body separate from each of the vocabularies' owner groups and what will be the ownership of any common, abstract set of classes, structures or types the central body produces. Good topic :-) -- Stephen Green Partner SystML, http://www.systml.co.uk Tel: +44 (0) 117 9541606 http://www.biblegateway.com/passage/?search=matthew+22:37 .. and voice On 21/11/2007, Costello, Roger L. <costello@m...> wrote: > Hi Folks, > > I am documenting the different approaches for extending the semantics > of a community's tag-set. I seek your thoughts on this topic. > > Let me start with an example to illustrate what I mean by "extending > the semantics of a community's tag-set." > > EXAMPLE > > Community #1 has defined a set of tags for expressing a person's > contact information. Here's an XML document that shows their XML > vocabulary: > > <?xml version="1.0" encoding="UTF-8"?> > <Point-of-Contact> > <Name>John Smith</Name> > <Address> > <Street>10 Tremont St.</Street> > <City>Boston</City> > <State>MA</State> > </Address> > <Telephone>617-123-4567</Telephone> > </Point-of-Contact> > > Everyone in Community #1 understands the semantics of this collection > of tags, so within their community they merrily interoperate. > > INTEROPERATING WITH OTHER COMMUNITIES > > At some point in time, Community #1 recognizes that to grow and thrive > they must extend beyond their little island of members and must > interact with other communities. Unfortunately for Community #1, those > other communities use different tags to represent a person's contact > information. > > Below are 3 approaches that Community #1 may take to bridge the gap > with the other communities. > > 1. OUT-OF-BAND SEMANTIC RESOLUTION > > The first approach is for Community #1 to leave their XML documents > intact, as they are, and to bridge the gap by building a translator -- > for example, an XSLT stylesheet that maps Community #1's tag-set to > Community #2's tag-set (and a translator to Community #3, #4, and so > forth) > > Advantages > > a. No impact to the XML documents exchanged within Community #1. > > Disadvantages > > a. Lots of translators need to be built and maintained ($$). > > 2. MIMIC THE HTML MODEL FOR EXTENDING SEMANTICS > > The HTML specification says that the class attribute may be used for > "general user agent processing." So, by adding class names to > elements, authors are able to expand the semantics of the language. > > Let's see how Community #1 can exploit this idea of using class > attributes to extend the semantics of their elements. Suppose that > Community #1 knows that some other communities use the vcard > specification for representing a person's contact information. > Thus, Community #1 extends the semantics of their XML vocabulary as > follows: > > <?xml version="1.0" encoding="UTF-8"?> > <Point-of-Contact class="vcard"> > <Name class="fn">John Smith</Name> > <Address class="adr"> > <Street class="street-address">10 Tremont St.</Street> > <City class="locality">Boston</City> > <State class="region">MA</State> > </Address> > <Telephone class="tel">617-123-4567</Telephone> > </Point-of-Contact> > > Note that a class attribute has been added to each element, and the > value of each class is a vcard term. > > Now Community #1 can interoperate with any community that understands > vcards. And, of course, within Community #1 they can simply ignore the > class attributes, since the semantics of the elements are already > understood. > > The HTML specification also says: "Multiple class names must be > separated by white space characters." So, the class attributes can be > used in a polymorphic way to support other communities. For example, > suppose some other communities use the EDI terminology for representing > a person's contact information. Community #1 can accommodate those > communities as well: > > <?xml version="1.0" encoding="UTF-8"?> > <Point-of-Contact class="vcard POC"> > <Name class="fn contact-name">John Smith</Name> > <Address class="adr location"> > <Street class="street-address mailing-address">10 Tremont > St.</Street> > <City class="locality district">Boston</City> > <State class="region province">MA</State> > </Address> > <Telephone class="tel">617-123-4567</Telephone> > </Point-of-Contact> > > Note that each class attribute now has two values: a vcard term and an > EDI term. > > Now Community #1 can interoperate with any community that understands > vcards, as well as any community that understands EDI. And, of course, > within Community #1 they still ignore the class attributes, since the > semantics of the elements are already understood. > > Additional extensions can be made to the class attributes to support > other communities. > > Advantages > > a. The semantic extensions are embedded within the document (in-band); > no translators needed. > > Disadvantages > > a. Community #1 must extend their XML vocabulary to support the class > attribute on each element, and define its semantics similar to how HTML > defines it. > > 3. UNIVERSAL XML VOCABULARY > > The third approach is for all the communities to get together, throw > out their existing tag-set, and get everyone to agree to use one, > standard, universal tag set. > > Advantages > > a. No interoperability problems > > Disadvantages > > a. Difficult to get disparate groups with their own self-interests to > forego their investments and agree to adopt a single, universal > tag-set. > > QUESTIONS > > I. Are there other approaches that aren't captured above? > > II. Can you expand upon the advantages and disadvantages of the above > approaches? > > III. Which approach do you prefer? Why? > > /Roger > >  http://www.w3.org/TR/html401/struct/global.html#h-7.5.2 >  http://www.imc.org/pdi/vcard-21.txt > > _______________________
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