Measuring the Capacity of an XML Schema: Specifying an Information Channel with an XML Schema

Fundamental concepts for measuring the amount of information specified by an Extensible Markup Language (XML) Schema are presented. A web service or XML application can use an XML Schema to specify the form of XML data allowed to invoke the service or application. The XML Schema may be viewed as a specification of an information channel to the web service or application. The capacity of the information channel specified by the XML Schema can be numerically measured. Knowledge of the capacity of a channel specified by an XML Schema is beneficial for web services and XML applications. The capacity indicates how much effort might be required by a web service or application to process XML instances, thus serving as an indicator of the potential load on the web service or application. Knowledge of the capacity of a channel specified by an XML Schema is also beneficial for security services that regulate against undesirable information exchanges. The amount of regulation required is proportional to the variety of information received. Thus, XML data conforming to an XML Schema that has a large capacity will require a comparatively large effort to regulate. As a general rule, the higher the capacity, the larger the security risk.