Existing Wording
There are two categories of data type: simple / primitive types, imported from XML schema, and complex types, which are re-usable clusters of elements.

Proposed Wording
There are two categories of data type: simple / primitive types (imported from XML schema), and complex types, which are re-usable clusters of elements.

Comments
The original wording/punctuation makes it sounds like there are THREE categories: 1. "simple/primitive" 2. "imported from XML schema" and 3. "complex types." The revision is clearer

Grahame's Comments
agree