[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Announce: Topic Map Standard out for Final Committee Draft Ballot
At 08:48 AM 11/14/98 -0800, Dave Winer wrote: >What kind of applications would we use the Topic Map structures for? > >It always helps me to understand this kind of stuff if I can understand a >compelling application for it. A topic map consists, fundamentally, of two kinds of things: topics and associations. A topic is an object that represents a single rhetorical topic or subject. For example, "XML parser" might be one topic in a topic map about XML. A topic serves to associate the abstract idea of the topic with occurrences of that topic: <topic xml:link="extended" role="topic" id="xml.parser"> <name> <basename>XML Parser</basename> </name> <occur xml:link="locator" role="parser-instance" href="http://www.jclark.com/xp"/> <occur xml:link="locator" role="parser-instance" href="http://www.microsoft.com/msxml/"> </topic> Notice that this serves to impose the semantic label "XML Parser" onto the occurrences addressed by the occur element. Thus a topic can assert that a given object is an occurrence of some kind of thing. This lets you construct a classfication or descriptive layer on top of existing data. The topics essentially represent opinions about the data. Different topic map authors might express different opinions about the same data. Because the form the opinions are expressed in is standardized and consistent (topics), they can be reasonably compared to some degree. Because the topics are expressed formally as hyperlinks (here using Xlink, but also doable using HyTime), they are naturally navigable using whatever hyperlinking support you have lying about (e.g., HyBrick, PHyLIS, etc.). Associations relate topics to each other. To continue the XML topic map idea, might have a relation "standard-interface-for" that I use to relate the topic "XML parser" to the topic "SAX": <assoc role="standard-interface-for" xml:link="extended"> <assocrl role="parser" href="#id(xml.parser)" xml:link="locator"/> <assocrl role="interface" href="#id(sax)" xml:link="locator"/> </assoc> In many ways, this is like RDF: you can impose properties onto data objects and relate data objects together using typed links. It may be that topic maps are one way to express RDF abstractions, I don't know (I don't know enough about RDF). But while RDF seems to be designed primarily to support the addition or representation of metadata about objects, topic maps are designed for the creation of knowledge bases imposed on data of any type, and, in particular. In any case, Topic Maps are not intended to compete with RDF--they are, in essence, different views of the same abstraction: objects with properties and relations among them. So what would you use topic maps for? I think one compelling use is as an annotative or descriptive layer over things like encyclopedias, dictionaries, databases, and the like. They might be used to enhance management information systems by providing a simple but rich and standardized way to capture analysis applied to existing data, such as market reports, sales numbers, etc. Topic maps can be a way to augment search and retrieval by providing a form of index over a larger, more amorphous body of data. Many documents can be turned into topic maps simply by labeling the existing components as topics. For example, you can think of a command reference document as a topic map where every command description is a topic. The reason for standardizing this concept is that it lets you build generic topic map engines that understand the specific properties of topics and associations and can therefore manage knowledge of those properties in a crisp and efficient way, making the information available to processing systems. It also allows the meaningful and automatic merging of topic maps because it's clear how the components of each relate to each other as objects. I'm not sure I've answered the question very well, but maybe I've provided enough of a taste for what topic maps do that applications will suggest themselves. I've left out a number of important and interesting details in the discussion above, but I think I've conveyed the flavor. Cheers, Eliot -- <Address HyTime=bibloc> W. Eliot Kimber, Senior Consulting SGML Engineer ISOGEN International Corp. 2200 N. Lamar St., Suite 230, Dallas, TX 75202. 214.953.0004 www.isogen.com </Address> xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
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