BPMN21 — Use XPath 2.0 as default expression language instead of XPath 1.0

XPath 1.0 is the default expression language in BPMN 2.0. Instead of XPath 1.0, the default expression language should be XPath 2.0 which is a W3C Recommendation since 14 December 2010 (and I assume that is why it has not made it into BPMN 2.0).

A major problem with XPath 1.0 is its limited set of functions. For instance, XPath 1.0 does not provide any time-related functions. Consequently, it is impossible to get the current system time in an expression, which might be necessary in Timer Events, without proprietary extensions to the standard. This harms portability of process models and is especially relevant for Process Execution Conformance. XPath 2.0 provides such functions and the time-related data types used in both, BPMN 2.0 and XPath 2.0, are identical (ISO-8601).

This change might affect several parts of the specification:
In section 10.3.3 The usage of XPath as expression language in BPMN 2.0 is discussed. There, several additional XPath-functions are defined, mentioning deficiencies in XPath 1.0. These functions should be redefined with XPath 2.0.
Section 14 Mapping BPMN Models to BPEL might also require changes. XPath 1.0 is the default language required by BPEL 2.0 and XPath 2.0 functions that are not present in XPath 1.0 cannot be mapped as easily.

I would strongly recommend for BPMN 2.0 to require the support for XPath 2.0 instead of XPath 1.0 as default expression language.