The value of the "name" attribute in the "param" element will correspond to the name of the context variable in the policy. This element will initialize the variable "foo" in the context of the XSL transformation and set it to the current value of the context variable "foo" in the service policy." The XSL transformation parameter "foo" will then have the value of "bar."
A policy author can then leverage this variable in an XSL transformation with a separate element: <xsl:value-of select="$foo"/>. Note that the variable prefix "$" is used in this context. This specified that "foo" is a context variable to the Gateway's XML message processor.
Policy context variables can also be referenced in an XPath evaluation with the following syntax: [local-name() = $varName]. In this circumstance, a reference to a context variable in policy ("varName") is set in the XPath assertion. If a policy author needed to use a context variable during the evaluation of an XPath then the syntac would be /foo/bar/*[local-name() = $varName].