XHTML by Example

Syntactic Conventions

The first thing that should be noted is that abstract module definitions are not written in a formal grammar. However, the W3C has borrowed conventions that should be familiar to the authors of DTDs.

Each module might be viewed as a table with three columns. In each row, you'll find an element, the attributes allowed within the element, and then the minimal content model for the element. A minimal content model might contain a list of elements, a content set (which is of itself a common list of elements), or a datatype such as PCDATA for the title element.

Occurrence indicators and other expressions will be found in the minimal content models as follows:

Expression	Meaning
Foo ?	Zero or one instances of foo are permitted. ...