Topic maps has its roots in back-of-the-book indexing. Each term in the back-of-the-book index points to a page in the book about that subject. Each term in a topic map points to other resources, plus a description about a link to the resource. In other words, there are 3 components in a topic map relationship. The extra relationship component makes it different from the back-of-the-book index or simple tagging with categories.
Topics, associations, and occurrences
Topics are the main building blocks of topic maps. Topics can be used to represent many things. It could be a subject, a person, an idea, etc. Topics are connected to each other through associations. Associations represent the relationships between topics. In the back-of-the-book index analogy, an association is the cross reference between index terms. Besides linking to other topics, a topic in a topic map can also link to other information resources. Such resources are called occurrences of the topic. An occurrence could be many things. For example, if you have a topic about a drug like Aspirin, an occurrence could be a research paper published in a scientific journal, a note in your database about Aspirin, a Web page on the Internet, a picture file of the pill, etc.
In Biblioscape, topics, associations, and occurrences are all represented by categories in the categories module. When you link one category to another, and assign a third category as the line type, then the third category is considered an association. When you link a category to a reference or a note and assign another category as the link type, then this category is considered an occurrence.
Topic types
Topics can be typed. There are no pre-defined sets of types. The typing is totally controlled by end users according to their needs. For example, if you plan to add many cities in different continents as topics, you can create a topic type called "Continent" and another one called "City". You can then assign one as a topic type for another topic. You can assign the topic type "City" to topics "Beijing" and "Tokyo". Remember, the topic type "City" itself is a topic. You can have an unlimited number of topic types.
Not only can you type topics, you can also type associations and occurrences. For example, you can create a category named "Tourism" and assign "Occurrence Type" as its type. Next time you link a category to other information objects like references, notes, etc., you can pick "Tourism" as the link relationship.
To create an association type, follow the same steps. First create a new category, and select "Association Type" as its type. When you create a link from a category to another category, you can select this "association type" category as the link relationship. In the above example, the category "has direct flight" is created as an association type.
Create associations and occurrences
In the above examples, we have created topics such as "Beijing" and "Tokyo". We have created occurrence types like "Tourism" and "History". We have also created association types like "has direct flight". They are all created as categories. It is time to link them together to create a knowledge map. First, select the category "Beijing". Click menu command "Category | Create Links | Link to Note...". The link window will be displayed. First, select the notes you want to link to in the middle panel. Then, go to the "Topic Maps" tab on the right panel. Select "Tourism" as the "Link type". Since we are linking to resources instead of another category, only those categories typed as "Occurrence Type" will be listed in the "Link type" combo box. Click the "Add Links" button to create the links. The newly added links will be shown at the bottom panel.
Associations are created in a similar way. First select "Category" on the top right corner as the "Link to" module. In topic maps, only when you link one topic (category) to another topic (category) is the link is called an association. Select categories you want to link to in the middle panel. In this example, we selected "Tokyo" and "London". Select "has direct flight" as the "Link type". When you link to another category, only association types can be selected as the "Link type". Click the "Add Links" button to create links.