Introducing XML Topic Maps - XTM
Topic Maps (XTM) is an XML grammar for interchanging internet based topic maps.
The primary aim of XTM is to improve the search of information over the web. XTM
describes the interconnected resources in the web. They make the searching of
documents on a particular subject much easier since the related materials can
be retrieved easily using XTM.
XML Topic Maps (XTM) represents the structure of information resources and this structure is used to define topics and their association between different topics. The characteristics of topics are its names, resources and the relationships. Topics have their characteristics within their scope. Scope of a topic defines the limited context within which the characteristics of topics are found. The documents which use the XML Topic Maps (XTM) grammar to relate them is called the topic map
The syntax for the XTM document is defined in the XML Topic Maps (XTM) specification. The structure of an XTM document will look as given below:
In the above code the topic element is used to define the topic of the subject and its occurrence. A topic element can have optional child elements like <instanceOf>, <subjectIdentity>, <baseName> and <occurrence>. The topic tag can have an id attribute to identify the topic. The <baseName> tag gives a name to the topic specified. There is a possibility for the same topic id to have different base names. For example if the topic id is vegetables, it can have names like Carrot, Beans etc. The <occurrence> element of the topic gives the different resources available for a particular topic. The different resources that the occurrence element refers to is given by the <resourceData> or <resourceRef> tags within the <occurrence> element.
The <association> element in the topic maps is used to relate or associate different topics. The association element can have child elements like <instanceof> and <member>. The members of association are those topics which need to be realated to one another in some form or another.
The <mergeMap> tag is used to merge different topic maps to the current topic map. For this purpose the xlink:href attribute is used in the topicRef tag. An example of code for mergeMap is given below:
In the above code the mergeMap tag is used to merge the topic map vegetables.xtm with the current topic maps by adding the topics Carrot and Beans to the scope of all characteristics in the vegetables.xtm topic map.
Some of the commonly used elements in topic maps are given below:
: Reference to a Topic element
The XML Topic Maps (XTM) specifications can be referred for more detailed information and samples on each of these elements.The concept of XTM is used to improve the searching of documents of the web since the related document can be retrieved quickly and easily with the help of XML Topic Maps.
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