Extra Features : Scopes, Slots, Topic Types
Topics, Associations and Occurrences can also be assigned one or more Scopes.A Scope is some kind of tag that you can assign to your topics, associations and occurrences. It defines a knowledge sub-domain, and allows the segmentation of large topic maps into different areas, easing up the navigation and the filtering of information: navigating the topic map using, for example, the astronomy scope will only show Topics, Associations and Occurrences belonging to that scope, hiding the other topics, associations and occurrences. Nevertheless, you're not forced to assign a scope to a topic. Such a scopeless topic will always be visible, whatever the scope you choose to browse your knowledge base. What's more, you can browse your knowledge base without selecting any browsing scope. In such a case, no filtering will be applied on the display, and all topics, associations and occurrences will be displayed, whatever the scope they're assigned.
Note that the 'No Scope' scope is called the 'Unconstrained Scope' in the Topic Map ISO standard. We'll use this term again throughout this manual.
Note also that a scope is, by itself, a regular topic; so one can create new scopes when needed, and assign them afterwards to new topics, associations and documents.
Another nice feature is the Topic's Slots or 'Properties as we will call them. It's in fact a properties list linked to a topic. These properties are defined as couples of "property name"/"property value", and a single Topic can be assigned an unlimited number of these properties.
In our example (see graph below), we defined three properties in the planet topic: the diameter, mass and orbital period of the planet. This shows that these slots are designed to store short data such as dates, numbers, small strings..
Last interesting feature, the Topic Type. Any Topic can be defined as an instance of one or more Topic Types – or Class.
The available Classes are, of course, regular topics, so that one can create his own Classes. And of course, a single Topic can be an instance of an infinite number of classes, and a class can have an infinite number of instances.
In our example (see graph below), we can see that Earth and Mars are instances of a Planet class. That Planet class has itself a moon subclass; and the Moon topic is an instance of that moon subclass...
