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Subject: [topicmaps-comment] RE: Ontological extravagance in the Topic MapGraph?
Why are so many different types of nodes, arcs, non-node and non-arc objects needed in the topic map graph? According to tmpm4, the topic map graph has the following entities: three types of node (topic, association and scope) and four types of arc (association-member, association-scope, association-template and scope-component). There are also the non-node subject identity points and the non-arc links between topic nodes and subject identity points, both of which are outside of the graph, but are nonetheless part of the ontology defined by tmpm4. It is possible to represent the same set of graphs with a smaller ontology, specifically: three types of node (topic, association and literal) and one type of arc (association-member). Association-scope and association-template arcs are here represented by association-member arcs, labelled (i.e. with 'role' specified) as 'scope' and 'template' respectively. Subject identity points are represented as literal nodes (with resource being a special case of literal), and topic nodes are linked to these literal nodes via association-member arcs. Presumably there were reasons to introduce the reified nodes and arcs (i.e. scope nodes, and association-scope, association-template and scope-component arcs) and to create ill-defined non-graph appendages (i.e. the subject identity points and the links to them). However, not only do they complicate a simple ontology, they increase the distance between graphical representation of topic maps and RDF. Simple graph ontology and simple RDF-TM links both seem like reasonably good ideas. So, why such a complicated ontology? Ivan Ivan Uemlianin, PhD Head of Topic Map Development Jura Technology Limited 6 Tai Seion Llanddeiniolen Caernarfon Gwynedd LL55 3AF Wales, UK Head Office: 35 Norroy Road Putney London SW15 1PQ UK
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