Add support for multiple expression languages

From W3C XForms Group Wiki (Public)

Make the expression language pluggable

Different users prefer different languages to write their queries and calculation expressions. XForms 1.1 supports only XPath 1.0 for its query (to specify node sets and refer nodes), constraint and calculation language. Examples of languages that could be used as query, constraint and calculation languages are XPath 2.0, javascript (for example using ECMAScript for XML)