Abstract: A cache system for storing request messages expressed in Extended Markup Language (XML) and the responses to those messages. The inbound request message, which typically takes the form of an HTTP request message containing an XML request document as its payload, is received via the Internet from a remote sender. The XML request portion of the inbound message is then translated into canonical form, preferably conforming to the predetermined standard canonical form established as an Internet standard. The canonical XML request is then compared with previously received canonical requests. To speed the process of comparing the inbound canonical XML request with previously cached XML requests, an access key, such as a checksum or a hash integer, is generated from the content of the inbound request. The access key is then used to identify zero or more prior canonical requests which may match the inbound canonical request.