Subject: Issue 143 - Proposal For Vote
143 - StaticSwitch Activity Proposal: Add static switch to BPEL Rationale: This is a very common programming construct that has proved its value over the years. It is particularly useful when needing to evaluate enumerated values. In XPATH it turns out that it's always possible to compare any two values no matter what they are and get a Boolean result. But this may not be true for other expressions languages so I put in a general requirement that staticSwitch's be statically analyzed to determine if the values used can be compared. However one can imagine languages where even a static check might not be possible. In theory we could cover that case by defining a special 'illegalCaseMatch' fault but I'm not convinced we need to do that work now. 12.X Static Switch <staticSwitch standard-attributes> standard-elements <condition expression-language="URI">expression</condition> <case value="xs:string">+ activity </case> <otherwise>? activity </otherwise> </staticSwitch> The staticSwitch activity evaluates the expression and then compares the returned value to the string values recorded in each case in term. The details of how the comparison is carried out is expression language specific. If the string value in a case matches then the activity in that case is executed and the staticSwitch exits. If no case matches and there is an otherwise then the activity in the otherwise is executed and the staticSwitch exits. If no case matches and there is no otherwise then the static switch exits without taking any action. BPEL processors MUST statically analyze BPELs and refuse any that return a value for the condition expression that cannot be compared to the values in the case statements using the language specified for the general expression. If the condition language is XPATH 1.0 then in effect each case statement contains an expression of the form "expression = xs:string". If the resulting value is true then the case matches, otherwise it does not. XPATH 1.0 is defined in such that such an expression is always legal, if not always useful.