Schema types for expressions

Section 8.3 list five kinds of expressions: boolean, deadline, duration, unsigned integer and general expressions.

In the XML Schema there is a general tExpression type with five sub-types: tBoolean-expr, tDeadline-expr, tDuration-expr, tCondition and tBranches.

Having tCondition as a special type of boolean expression for join and transition conditions seems reasonable, since the are evaluated diffenrently that ordinary boolean expressions.

tBranches is a special case of an unsigned integer expression, used in the completion condition of the forEach activity.

Why is there no sub-type of tExpression to represent unsigned integer expressions in general, as used in startCounterValue and finalCounterValue of forEach? tBranches could have been a sub-type of this.

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