Subject: Re: [wsbpel] Issue 107 - Proposal to Vote (pending 82)
Here it is again, without changelog. This is a proposal to vote, pending 82 passing with same concepts. Expanding on Peter's existing 107 proposal (details, syntax, examples), assuming concepts in 82 (base+profiles) : ---------------------------------------------------------------- 15.1 Language extensions for Abstract Processes The language extensions consist of opaque tokens which are used as explicit 'placeholders' for missing details. Note that "opaque" is not a new semantically meaningful construct but a syntactic device for indicating incompleteness. As such, "opaque" entities have no semantics of their own. There are three kinds of opaque placeholders: expressions, activities, and attributes. A usage profile may restrict the kinds of opaque tokens allowed at its discretion. For example, a profile could specify that it allows only opaque activities, but not opaque expressions and attributes, or a profile could specify that it allows all attributes to be opaque except the “partnerLink” attribute. However, a usage profile may not expand it above what is allowed by the "common base". For example, a profile cannot specify that it allows <faultHandler> elements to be opaque. -Under the 'common base' section --------------------------------- Three types of opaque tokens are allowed in abstract processes: activities, expressions, and attributes. The functions of these opaque placeholders are described below, with examples: Part A - Opaque activities: An opaque activity explicitly is a placeholder for exactly one executable BPEL activity (not counting any activities that could be nested within that single executable activity) whose behavior is not relevant to the recipient/user of the abstract process. An opaque activity is a BPEL activity and therefore has the same standard elements and attributes that all BPEL activities have (see spec section 11.1 and 11.2). It has the following form: <opaqueActivity standard-attributes> standard-elements </opaqueActivity> One examples of using opaque activities includes creating process templates (marking the points of normative extension in a process). Another is when creating an abstract process from a known executable process and wanting to hide an activity that is a join point for several links. If that activity, on the other hand, had just been an unlinked activity in a 'sequence' it could have just been omitted from the resulting abstract process. At first glance, it seems that this could instead be done using <empty>. The difference is that <empty> explicitly says "nothing happens here," whereas <opaqueActivity> is really saying "something happens here, but it's hidden on purpose". A.1 Opacity of activities allowed in the base: Opaque activities are allowed. PART B - Opaque expressions: Opaque BPEL expressions shall be allowed exclusively for the use of abstract processes. An opaque expression explicitly hides a corresponding executable BPEL expression. An example usage of an opaque expression is that of copying a hidden value into a known variable. Opaque assignment can be used to express non-determinism: the obvious case being a process that needs to show a decision point with alternative outcomes without specifying how the decision is reached. In this case the expressions that constrain each branch may need to be left unspecified, but it may also be convenient to make a specific value or quantity such as a price threshold unspecified, so that explicitly specified conditions relative to the threshold become non-deterministic as a result of the threshold value being unknown. All expressions in BPEL, and their corresponding opaque representations are listed below: 1-Boolean valued expressions: -Transition Condition: <transitionCondition expressionLanguage="anyURI"? opaque="yes"/> -Join Condition: <joinCondition expressionLanguage="anyURI"? opaque="yes"/> -While Condition: <condition expressionLanguage="anyURI"? opaque="yes"/> -Switch Case Condition (editors’ note: reflect new if-then-else syntax) : <case> <condition expressionLanguage="anyURI"? opaque="yes"/> activity </case> 2- Deadline valued expressions: -Until element of onAlarm and wait: <until expressionLanguage="anyURI"? opaque="yes"/> 3- Duration valued expressions: -For element of onAlarm and wait: <for expressionLanguage="anyURI"? opaque="yes"/> -repeatEvery element of onAlarm: <repeatEvery expressionLanguage="anyURI"? opaque="yes"/> 4- Opaque From-Spec in Assignment: (Issue 103) <from expressionLanguage="anyURI"? opaque="yes"/> is allowed, and represents hiding any of the forms of the 'from-spec'. -Opaque assignment (<from opaque="yes"/>) is used for capturing variable creation/modification in a yet-to-be-concretized mechanism/fashion. See section 9.3. (editor’s note: update with any new expressions from any new activities) B.1 Opacity of expressions in the common base: All BPEL expressions are allowed to be opaque. The generic form of opaque assignment is also allowed. PART C - Opaque attributes: An opaque attribute hides the value of an executable BPEL attribute. For example, an opaque variable attribute in a receive activity hides where the data is stored once the corresponding message is received. The reserved value “##BPELopaque” shall be made available for use as the value of any BPEL attributes in a BPEL abstract process that can be opaque. (editor’s note: this may change to make sure have a value for attribute types based on XSD. C.1: Opacity of attributes in the common base: All BPEL attributes are allowed to be opaque in the common base. --------- Rania's note on spec editing : if 82 passes, then A.1, B.1, and C.1 could go in the bullets of the common base where it says that it depends on 107.