Release 10.1A: OpenEdge Development:
Web Services

SOAP message headers—an overview

A SOAP request message or a SOAP response message can contain an optional <Header> element (header) that passes non-parameter information about the Web service or the operation that generates it. This header can contain one or more header entries. A header entry contains certain information defined by the Web service that is necessary to properly invoke some or all of its operations.

A header returned by the Web service in a SOAP response message is a SOAP response header. A header sent in a SOAP request message by invoking a Web service operation is a SOAP request header. Syntactically, there is no difference between these two types of headers. However, keeping them conceptually separate helps to clarify how you can manage them for a Web service operation. For a given operation, the content of any SOAP request header can be different from that of any SOAP response header.

Why are headers necessary if operations already pass data as parameters? Headers can simplify the management of data for users of certain Web services that require the management of context (such as user authentication) during the course of Web service interaction. With the use of headers, the mainline of a client application need have no concern about maintaining these states. The Web service provider typically provides specific information about the content of headers and how they must be handled by client applications. The client can then provide special header handlers, which are callback procedures that manage the content of these headers for the Web service application.