Re: [Gzz] RE: [ba-ohs-talk] Fenfire, RDF (re "Towards a Standard Graph-Based...")
At 02:00 PM 3/8/2003, Benja Fallenstein wrote:
>I got that impression from the TAO document. In all the diagrams, topics
>are shown as objects floating above a tissue of 'occurences,' resources in
>which the topic occurs. And the document contains language like the following--
> An important point to note here is the separation into two layers of
> the topics and their occurrences. This separation is one of the
> clues to the power of topic maps and we shall return to it later.
>I may have misunderstood the doc, of course.
>- Benja (01)
I doubt that you misunderstood the doc; it is a well-written document and
what was written might not lead you to realize that it is also possible to
"reify" occurrences in topics, thus making topics out of individual
resources, with which you can form associations, decorate with properties,
and so forth. Reified occurrences are discussed in the _XML Topic Maps_
book, and, I suspect, in various places on the Web. (02)
Occurrences can do this by way of the <instanceOf> tag. At
we see: (03)
occurrence type (04)
1. One of the classes of topic occurrence.
2. The class of topic occurrence specified by an <occurrence>
element's <instanceOf> child element. An occurrence may belong to only one
3. A topic whose subject is a class of topic occurrence. (05)
The topic, the subject of which is the occurrence itself, leaves plenty of
room for further annotation. Consider a topic, say, "Topic Map" which has
an associated topic, say, "Literature", which itself, contains several
occurrences, some of which are type "Book" (another topic), some of which
are of type "Conference Paper", and so forth. Within that ontology, it is
possible to subclass, say, "Book" to a particular book and decorate that
topic with all sorts of associations. HyTM (the older hytime version of
topic maps) used to have something called <facet> which served the same
purpose as "facets" do as restrictions on "slots" in "frames". Facets got
dropped during development of XTM. (06)
Hope that helps.
XML Topic Maps: Creating and Using Topic Maps for the Web.
Addison-Wesley. Jack Park, Editor. Sam Hunting, Technical Editor (08)
Build smarter kids globally to reduce the need for smarter bombs. (09)