Some basic Topic Maps terminology

<< 2006-11-14 19:19 >>

There are some simple, common terminological mistakes people tend to make when they first encounter Topic Maps, and I thought it might be useful to write up a simple guide to help people.

Topic

Many people think topics are things like "person", "country", and "company", but not things like "Lars Marius Garshol", "Norway", and "Ontopia", but this is wrong. The confusing answer is that all of these things are topics. The first three are topic types (which are topics), and the last three are instances of those types.

In other words, a topic is a thing you talk about in your topic map. Most topics have a topic type, but some of them are topic types. The thinking is that the types are also things, which you may want to say something about.

Topic names

This is another thing that people tend to be confused about, but it's really very simple. A topic name is just the name of some topic, and it's attached to the topic in the same way that occurrences and associations are. A topic can have more than one name. For example, the topic representing me could have the names "Lars Marius Garshol", "larsbot" (nick), and "larsga" (username) attached to it. It would still be a single topic, but it would have three names.

In a sense, topic names are not very different from attaching property occurrences like "date of birth" and "phone number".

Ontology

This term has a special usage in Topic Maps that's different from how it's used elsewhere. In the Topic Maps community it's used to mean the typing topics in a topic map. That is, the topic types, association types, and occurrence types that are used. (It's kind of like the database schema in a relational database.)

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