Web Services Essentials

Header

The optional Header element offers a flexible framework for specifying additional application-level requirements. For example, the Header element can be used to specify a digital signature for password-protected services; likewise, it can be used to specify an account number for pay-per-use SOAP services. Many current SOAP services do not utilize the Header element, but as SOAP services mature, the Header framework provides an open mechanism for authentication, transaction management, and payment authorization.

The details of the Header element are intentionally open-ended, thereby providing maximum flexibility for application providers. The protocol does, however, specify two header attributes:

Actor attribute

The SOAP protocol defines a message path as a list of SOAP service nodes. Each of these intermediate nodes can perform some processing and then forward the message to the next node in the chain. By setting the Actor attribute, the client can specify the recipient of the SOAP header.

MustUnderstand attribute

Indicates whether a Header element is optional or mandatory. If set to true,^[5] the recipient must understand and process the Header attribute according to its defined semantics, or return a fault. (See Table 3-2 for the MustUnderstand fault code.)

Here is an example Header:

<SOAP-ENV:Header>
   <ns1:PaymentAccount xmlns:ns1="urn:ecerami" SOAP-ENV:
        mustUnderstand="true">
      orsenigo473
   </ns1:PaymentAccount >
</SOAP-ENV:Header>

The Header specifies a payment account, ...