HP e-Commerce / XML director server appliance sa8250 - Users Guide

C H A P T E R 2 HP e-Commerce/XML Director Server Appliance SA8250 User Guide

Each element together with the operator selects a set of nodes in the

XML data tree relative to a context node. This set of nodes must

match the name of the element specified in a step. Every path starts

with the root node as the first context node. Nodes selected in a step

form the set of context nodes for the following step.

You can specify an element as “*”, which selects any element relative

to the context node. You can also specify an optional filter at the end

of a path to further refine XML data stream parsing.

Using the “employee” from the earlier XML data example, an XML

pattern on the SA8250 might look like this:

* & //address[zip > 90000]

where:

• * is a Layer 7 (RICH) wildcard expression

•

//address[zip > 90000] is an XML expression

For more information on XML patterns, see “XML Pattern Creation”

later in this chapter.

Because the server is configured for any zip codes greater than 90000,

and John K. Smith’s zip code is 92128, the SA8250 directs his

employee data to that server.

You can specify an attribute as @AttributeName, or @* to select any

attribute relative to the context node.

Filters are identified by a FilterExpression enclosed within square

brackets, [ ]. They define a pattern within a pattern following this

general structure:

( (’/’ | ’//’) Element )? [ FilterExpression ]

Filter expressions are applied to every element returned by the

preceding path pattern. They return a Boolean TRUE if the server is

a valid choice, or FALSE if that server will not be used.

An element or attribute by itself inside a filter expression specifies an

existence test. For example:

//a[b or @c]