CR — XSD attribute "processRef" MUST be required

According to Chapter 5.4.10.5 ProcessTask, Table 5.36 - ProcessTask attributes, the attribute 'processRef' (a reference to a Process) is required.
The XSD in OMG Document dtc/14-01-01 does not reflect this:
<xsd:attribute name="processRef" type="xsd:QName">

In my opinion is must be:
<xsd:attribute name="processRef" type="xsd:QName" use="required">

The same applies to definitionRef of tCaseFileItem.

So one of the two must be corrected: either the XSD or the class diagram.

Also I am wondering why 'use="optional"' is used at the attributes level quite often. I thought this is the default setting anyway.

Add definitionRef use="required" in XSD definition of tCaseFileItem

1. We should leave processRef optional because of resolution to issue CR-12 (make CaseRef and ProcessRef an expression)

2. Modify the XSD and define attribute "definitionRef" for tCaseFileItem as follows:
<xsd:attribute name="definitionRef" type="xsd:QName" use="required">