[jboss-jira] [JBoss JIRA] Commented: (BPEL-272) allow xpath expression/query to create more than one occurrence of an element

allow xpath expression/query to create more than one occurrence of an element ----------------------------------------------------------------------------- Key: BPEL-272 URL: http://jira.jboss.com/jira/browse/BPEL-272 Project: JBoss jBPM BPEL Issue Type: Feature Request Security Level: Public(Everyone can see) Components: Engine Affects Versions: jBPM BPEL 1.1 beta 3 Reporter: Alejandro Guizar Assigned To: Alejandro Guizar Priority: Critical Fix For: jBPM BPEL 1.1 GA PROBLEM The current XPath sublanguage implementation automatically creates nodes missing from location paths during assignment. This facility has a number of conceptual limitations. One of them is the inability to append a child element to an existing element if the latter already has a child element with the same name. There is no XPath syntax to express that a new element is required! It is tempting to think of a numeric XPath predicate as an array index, leading to the next snippet: <copy> <from><literal>haha</literal></from> <to variable='laughter' xmlns:ex='http://jbpm.org/bpel/examples'> <query>ex:laugh[last() + 1]</query> </to> </copy> However, such an interpretation of a predicate is wrong. Consider the following extract from XPath 1.0 specification on predicates: "A PredicateExpr is evaluated by evaluating the Expr and converting the result to a boolean. If the result is a number, the result will be converted to true if the number is equal to the context position and will be converted to false otherwise." The description of the last() function reads: "The last function returns a number equal to the context size from the expression evaluation context." Noticed the problem? The context position is never greater than the context size. Therefore the predicate [last() + 1] does not represent the position "one past the context size" but the boolean value false. Unfortunately, no other predicate seems appropriate. PROPOSAL Introduce a minor deviation from the XPath 1.0 specification. Interpret the result of a numeric predicate that equals the context size plus one as a request to create a new occurrence of the node.