Elaborate on default values

I.e. values that are textContent of XML nodes (in the primary instance)

1. Make clear these values are **not** expressions but constants.
2. Is there a "correct" way for a client to deal with default values that do not match the data type?

Start by locating the specification section that defines default values as textContent of XML nodes in the primary instance. Clarify that these values are constants rather than expressions, and document how clients should handle defaults that do not match the declared data type. Done means both questions are answered in the specification.

Written by the indexing model from the issue text.