This element contains application specific information about the SOAP message.

If the Header element is present, it must be the first child element of the Envelope element.

All immediate child elements of the Header element must be namespace-qualified.

The example above contains a header with a "Trans" element, a "mustUnderstand" attribute value of "1", and a value of 234.

SOAP defines three attributes in the default namespace ("http://www.w3.org/2001/12/soap-envelope"). These attributes are: actor, mustUnderstand, and encodingStyle. The attributes defined in the SOAP Header defines how a recipient should process the SOAP message.

By passing different endpoints along the message path, a SOAP message may travel from a sender to a receiver. Not all parts of the SOAP message may be intended for the ultimate endpoint of the SOAP message but, instead, may be intended for one or more of the endpoints on the message path.

The SOAP actor attribute may be used to address the Header element to a particular endpoint.

This attribute can be used to indicate whether a header entry is mandatory or optional for the recipient to process.

If you add "mustUnderstand="1" to a child element of the Header element it indicates that the receiver processing the Header must recognize the element. If the receiver does not recognize the element it must fail when processing the Header.

This attribute is used to define the data types used in the document. A SOAP message has no default encoding. The encodingStyle attribute may appear on any SOAP element.It will apply to that element's contents and all child elements.