More XMLMap: XML about Content (3/3) - exploring XML | WebReference

More XMLMap: XML about Content (3/3) - exploring XML

Book Review: "Practical XML for the Web"


What is an ontology, you ask? Well, according to Tom Gruber from Stanford, the short answer is: An ontology is a specification of a conceptualization. Hmmm... A more accessible definition I found reads: Ontology is the theory of objects and their ties. The unfolding of ontology provides criteria for distinguishing various types of objects (concrete and abstract, existent and non-existent, real and ideal, independent and dependent) and their ties (relations, dependences and predication).

Based on RDF, the DARPA Agent Markup Language + Ontology Inference Layer (DAML+OIL) provides a basic infrastructure that allows a machine to make the same sorts of simple inferences that human beings do. A set of DAML statements by itself (and the DAML spec) can allow to conclude another DAML statement whereas a set of XML statements, by itself (and the XML spec) does not allow to conclude any other XML statements. To employ XML to generate new data, knowledge embedded in some procedural code somewhere is needed, rather than explicitly stated, as in DAML. DAML was combined with a similar effort in this space more targeted to the Web environment, Ontology Interchange Language (OIL), to form DAML+OIL.

Building upon the foundations of the DAML+OIL specification, the W3C Web Ontology Language (OWL) "is intended to provide a language that can be used to describe the classes and relations between them that are inherent in Web documents and applications."

Topic Maps

The Topic Map Standard "provides a standardized notation for interchangeably representing information about the structure of information resources used to define topics, and the relationships between topics. A set of one or more interrelated documents that employs the notation defined by this International Standard is called a 'topic map'. In general, the structural information conveyed by topic maps includes:

  1. groupings of addressable information objects around topics (occurrences)
  2. relationships between topics (associations)
A topic map defines a multidimensional topic space -- a space in which the locations are topics, and in which the distances between topics are measurable in terms of the number of intervening topics which must be visited in order to get from one topic to another, and the kinds of relationships that define the path from one topic to another, if any, through the intervening topics, if any."

Topic maps were first formalized by the International Standards Organisation (ISO) as ISO 13250, based on SGML and HyTime. An adaptation to XML is being defined as XML Topic Maps (XTM).

Was it worth all the trouble? In search of the semantic Web, the designers expect that OWL will support the use of automated tools which "can use common sets of terms called ontologies to power services such as more accurate Web search, intelligent software agents, and knowledge management." Time will tell whether these interesting technologies will show up in browsers anytime soon.

Produced by Michael Claßen

Created: Feb 17, 2003
Revised: Feb 17, 2003