Content models

Within a content model:

  • sequence is indicated by comma
  • alternation is indicated by |
  • grouping is indicated by parentheses

Occurrence indicators:

[nothing] once ? optionally once
+ one or more times * zero or more times
If #PCDATA appears in a content model...
  • it can only appear once
  • it must appear first
  • if in an alternation, only the * occurrence indicator is allowed

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