SOA for the Business Developer: Concepts, BPEL, and SCA (Business Developers series)

Overview

This appendix describes the Business Process Execution Language (BPEL) 2.0 syntax for

• durations and deadlines

• basic activities

• structured activities

• functions

• additional constructs in the BPEL process

• BPEL extensions to Web Services Definition Language (WSDL)

This appendix uses grammar from the BPEL 2.0 specification (Web Services Business Process Execution Language Version 2.0), which is available at the following Web site: http://www.oasis-open.org/committees/documents.php?wg_abbrev=wsbpel. Here are some of the symbols and phrases that we reproduced from there:

• ? means 0 or 1 time. The element or attribute that precedes the symbol is optional and can appear only once.

• * means 0 or more times. The element or attribute that precedes the symbol is optional and can be repeated.

• + means 1 or more times. The element or attribute that precedes the symbol is required and can be repeated.

• Unless otherwise stated in this introduction, an element or attribute that is not followed by one of the aforementioned three symbols (?*+) is required and can appear only once.

• | means that the preceding and following characters are alternatives; for example, yes | no means a choice: yes or no.

• Various strings mean what they say, though you may need to add spaces or remove hyphens. For example:

  • activity is a BPEL activity.

  • anyURI is a universal resource identifier (URI); for example, you use a URI to specify the query language in an assign activity.

  • BPELVariableName is an XML identifier that is valid for a BPEL variable name; the identifier has no colon, period, or reverse virgule (\).

  • BPELVariableNames is a list of BPEL variables names with no intervening commas or other punctuation.

  • standard-elements refers to the BPEL elements sources and targets, as described in relation to concurrency (Chapter 7). Those elements are optional.

  • standard-attributes refers to the optional attributes name and suppressJoinFailure, as described in Chapter 8. Those attributes are optional.

• Parentheses isolate characters from other characters. In the next example, the for and until elements are alternatives, and a BPEL activity is required.

  ( <for expressionLanguage="anyURI"?>duration-expr</for> | <until expressionLanguage="anyURI"?>deadline-expr</until> ) activity

  A function name is followed by a single pair of parentheses, typed as is.

• expr is short for expression:

  • bool-expr resolves to true or false.

  • duration-expr resolves to a duration (described later).

  • deadline-expr resolves to a deadline (described later).

• QName is an XML qualified name, which is an identifier that can include an initial prefix and colon.

• QName-list is a list of XML qualified names with no intervening commas or other punctuation.

• NCName is an XML identifier that has no colon. (The NC came from the phrase no colon.)

Most examples do not include namespaces, but the distinction between QName and NCName gives you additional detail. The name of a port type, for example, is a QName, which means that the name can include a namespace prefix. The name of an operation, however, is an NCName, which means that the name cannot include a namespace prefix. In this case, BPEL relies on the namespace in a given WSDL definition being identical for the two names.