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

C H A P T E R 2 XML Operations
23
XML Pattern Matching
Please refer to this example XML command throughout this
discussion:
create */order.asp & doc=3 & //From[id="Acme"]
The SA8250 attempts to find XML pattern matches in the following
sequence:
1. RICH expression matches. If the RICH expression
(
*/order.asp) does not match, the document number and
XML expression are ignored.
NOTE: We recommend
using the same document
number in all XML
patterns with the same
RICH expression for a
service. If you specify
different document
numbers for each XML
pattern of the same RICH
expression, it could cause
degraded performance,
because a different XML
document has to be
parsed for each XML
pattern to be matched.
2. Optional document number matches.
doc=3 instructs the
SA8250 to use the third document for matching against the XML
expression. If the third document is missing, or is not an XML
document, the data is treated as a non-XML document and
directed to the first matching RICH expression server.
For more information on the document number, see “Document
Number Specification” later in this chapter.
3. Optional XML expression matches. If both the RICH and XML
expressions match, the SA8250 directs the client data to the
server matching the XML expression (
//From[id=”Acme”]).
4. If only the RICH expression matches, or the XML expression is
missing, the SA8250 either directs the client data to a default
server, or returns an HTTP error 503, “No Servers Available”
message to the client. This depends upon the SA8250’s
configuration.
For information on how to configure a default server, see Chapter
4.
For more information on RICH expressions, see “RICH
expressions in XML patterns” later in this chapter.
If any server in a service has undefined XML expressions, that server
will be used for any XML data sent to that service, regardless of
content. To prevent this, ensure that you define XML expressions on
all servers within a service.