RE: [wsbpel] Issue - 137 - Making properties consistent with variable va

This issue represents a misunderstanding of the semantics of properties in BPEL.

Properties are not akin to variables and are not set nor do they exist independently. A property “occurs” in a message. One can already get and set it in a message through getVariableProperty and property assignment. Thus the fragment “the variable is edited to change one PO into two. Now the NumOrder property, still set to the value 1” illustrates the misunderstanding.

Only correlation sets have independently set values, and they are set at the time of a web service interaction only.

Perhaps Issue 8 was not redundant after all ..

Satish

From: ws-bpel issues list editor [mailto:peter.furniss@choreology.com]
Sent: Wednesday, July 14, 2004 8:01 PM
To: wsbpel@lists.oasis-open.org
Subject: [wsbpel] Issue - 137 - Making properties consistent with variable values

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Issue - 137 - Making properties consistent with variable values

Status: open
Categories: Syntax and validation
Date added: 15 Jul 2004
Submitter: Yaron Y. Goland
Date submitted: 15 July 2004
Description: Currently a property's value is set when a variable is initially set. If the variable's value is subsequently changed then the property's value is not updated. Instead, once the property has been initially set, the state of the property and the state of the underlying variable are no longer correlated. Allowing for a disconnect between the property and its variable is all but guaranteed to lead to misunderstandings.

Imagine a variable that contains a purchase order and the NumOrder property which contains a count of how many orders are in the PO. Now imagine that after the variable is set and the property initialized then the variable is edited to change one PO into two. Now the NumOrder property, still set to the value 1, will no longer have the correct count of orders in the variable.
Submitter's proposal: 1) We should require that any time a variable's value is updated (e.g. with assign) that the property alias for all the properties on the variable should be re-run so the property values will be updated.

2) We should either ban assigning directly to properties or we should specify that properties that are not LValues (e.g. resolve to a single node in the underlying variable) are read-only and properties that are LValues can be written to but the consequence of doing so is that the node in the underlying variable is changed.
Changes: 15 Jul 2004 - new issue

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Issue - 137 - Making properties consistent with variable values