6.4. The Interchange Tag Language
Now we need a way to pull the template pieces we just created into the proper places to make a complete page. This is done using ITL, the Interchange Tag Language.
ITL is at the heart of almost all Interchange catalog pages. It's how you use Interchange's functionality. The ITL tags appear between square brackets like [this]. Options appear after the tag, separated by whitespace, like this: [tag option1 option2] and this: [tag option1=value1 option2=value2]. They can span multiple lines. (That can help readability when the tag has many options.) There are many ITL tags, and for this tutorial very few will be addressed. For a complete listing of the ITL tags, see the Interchange Tag Reference Guide.
Your first tag will be [include], which reads the file mentioned (relative to the catalog directory), parses any Interchange tags, and puts the result in place of the tag. This is demonstrated on the next page you need to create.