Differences in SOAP versions

Both SOAP Version 1.1 and SOAP Version 1.2 are World Wide Web Consortium (W3C) standards. Web services can be deployed that support not only SOAP 1.1 but also support SOAP 1.2. Some changes from SOAP 1.1 that were made to the SOAP 1.2 specification are significant, while other changes are minor.

The SOAP 1.2 specification introduces several changes to SOAP 1.1. This information is not intended to be an in-depth description of all the new or changed features for SOAP 1.1 and SOAP 1.2. Instead, this information highlights some of the more important differences between the current versions of SOAP.

The changes to the SOAP 1.2 specification that are significant include the following updates:
  • SOAP 1.1 is based on XML 1.0. SOAP 1.2 is based on XML Information Set (XML Infoset).

    The XML information set (infoset) provides a way to describe the XML document with XSD schema. However, the infoset does not necessarily serialize the document with XML 1.0 serialization on which SOAP 1.1 is based.. This new way to describe the XML document helps reveal other serialization formats, such as a binary protocol format. You can use the binary protocol format to compact the message into a compact format, where some of the verbose tagging information might not be required.

    In SOAP 1.2 , you can use the specification of a binding to an underlying protocol to determine which XML serialization is used in the underlying protocol data units. The HTTP binding that is specified in SOAP 1.2 - Part 2 uses XML 1.0 as the serialization of the SOAP message infoset.

  • SOAP 1.2 provides the ability to officially define transport protocols, other than using HTTP, as long as the vendor conforms to the binding framework that is defined in SOAP 1.2. While HTTP is ubiquitous, it is not as reliable as other transports including TCP/IP and MQ.
  • SOAP 1.2 provides a more specific definition of the SOAP processing model that removes many of the ambiguities that might lead to interoperability errors in the absence of the Web Services-Interoperability (WS-I) profiles. The goal is to significantly reduce the chances of interoperability issues between different vendors that use SOAP 1.2 implementations.
  • SOAP with Attachments API for Java™ (SAAJ) can also stand alone as a simple mechanism to issue SOAP requests. A major change to the SAAJ specification is the ability to represent SOAP 1.1 messages and the additional SOAP 1.2 formatted messages. For example, SAAJ Version 1.3 introduces a new set of constants and methods that are more conducive to SOAP 1.2 (such as getRole(), getRelay()) on SOAP header elements. There are also additional methods on the factories for SAAJ to create appropriate SOAP 1.1 or SOAP 1.2 messages.
  • The XML namespaces for the envelope and encoding schemas have changed for SOAP 1.2. These changes distinguish SOAP processors from SOAP 1.1 and SOAP 1.2 messages and supports changes in the SOAP schema, without affecting existing implementations.
  • Java Architecture for XML Web Services (JAX-WS) introduces the ability to support both SOAP 1.1 and SOAP 1.2. Because JAX-RPC introduced a requirement to manipulate a SOAP message as it traversed through the run time, there became a need to represent this message in its appropriate SOAP context. In JAX-WS, a number of additional enhancements result from the support for SAAJ 1.3.
  • The Web Services Description Language (WSDL) Version 1.1 specification does not discuss SOAP 1.2. SOAP 1.2 is discussed in the draft versions of WSDL 2.0. WSDL Version 1.1 only defines how to render a SOAP 1.1 payload in a WSDL 1.1 document. To resolve how to represent SOAP 1.2-based services, there is another W3C document that defines how to define a SOAP 1.2 payload within a WSDL 1.1 document. Read about WSDL 1.1 binding extensions for SOAP 1.2.
  • SOAP 1.1 is a single document. The SOAP 1.2 specification is organized in the following parts:
    • Part 0 is a non-normative introduction to SOAP.
    • Part 1 describes the structure of SOAP messages, the SOAP processing model and a framework for binding SOAP to underlying protocols. Conformant SOAP implementations must implement everything in Part 1.
    • Part 2 describes optional add-ins to the core of SOAP including a data model and encoding, an RPC convention and a binding to HTTP. Conformant SOAP implementations might implement any of the add-ins in Part 2. However, if add-ins are implemented, they must conform to the relevant parts of the specification.
    A fourth document is the Specification Assertions and Test Collection

SOAP 1.2 has a number of changes in syntax and provides additional, clarified semantics from those that are described in SOAP 1.1. The SOAP 1.2 Primer document lists and describes these syntax changes.