Occurrences and Resources

Having learnt that a topic can have any number of occurrences we are now going to find out what an occurrence itself can consist of. In general, information can be external to a topic map, such as references to web sites; or, they can be integrated directly into a map as a (short) text. In topic map terminology external resources are managed via resourceRefs while internal are captured by resourceData. Thus, the distinguishing feature between these two resources is that:

• the resourceReflinks to an external information resource
• the resourceDatais a short piece of information

Following along these lines, we find the following different resources for our Bond example:

<topic id="bond-uni">
  <instanceOf><topicRef xlink:href="#university"/></instanceOf>
  <baseName>
    <baseNameString>Bond University</baseNameString>
  </baseName>
  <occurrence>
    <instanceOf><topicRef xlink:href="#promotion"/></instanceOf>
    <resourceData>the best you can do</resourceData>
  </occurrence>
  <occurrence>
    <instanceOf><topicRef xlink:href="#webpage"/></instanceOf>
    <resourceRef xlink:href="http://www.bond.edu.au/"/>
  </occurrence>
</topic>

Each occurrence can have a type. instanceOf specifies the more general terms, which our resource belongs to. Contrary to resourceRef or resourceData, the instanceOf is optional within one occurrence.

Having introduced two new topics we have to define them

<topic id="promotion">
  <baseName>
    <baseNameString>promotion</baseNameString>
  </baseName>
</topic>

<topic id="webpage">
  <baseName>
    <baseNameString>webpage</baseNameString>
  </baseName>
</topic>

We also find different information resources regarding the IT-school:

<topic id="it-school">
  <baseName>
    <baseNameString>Bond School of Information Technology</baseNameString>
  </baseName>
  <occurrence>
    <instanceOf><topicRef xlink:href="#info-booklet"/></instanceOf>
    <resourceRef 
        xlink:href="http://www.bond.edu.au/it/publications/booklet/Bond%20It.pdf"/>
  </occurrence>
  <occurrence>
    <instanceOf><topicRef xlink:href="#web-main-page"/></instanceOf>
    <resourceRef xlink:href="http://www.it.bond.edu.au/"/>
  </occurrence>
</topic>

<topic id="info-booklet">
  <baseName>
    <baseNameString>Information Booklet</baseNameString>
  </baseName>
</topic>

<topic id="web-main-page">
  <baseName>
    <baseNameString>web main page</baseNameString>
  </baseName>
</topic>

In our examples above the recourceRef links to relevant websites, so they are all webpages. When the instanceOf refers to the general term "webpage", this does not add too much information. To be more specific about a particular reference, we used "booklet" and "web-main-page".

Each individual resourceRef or resourceData is embedded in its own occurrence. Do not list several websites within one occurrence.

In case of finding plenty of websites try to find out which one is really relevant to your specific topic. It does not make sense to confront the end users with a huge number of information resources which they cannot cope with. Therefore sort out the ones, which are less relevant and move them to another topic. Less is more.

The next section covers scopes which allow us to reduced of information to be presented to some topic map user.