Systems, methods and apparatus operate to receiving a markup processing program containing a set of markup processing instructions. Each markup processing instruction includes an operation defining a processing operation to be matched to a markup language representation and a corresponding action to be performed upon matching the operation to the markup language representation. The system receives the markup language representation containing encoded items representative of markup language constructs and executes the markup processing program in conjunction with the markup language representation to dynamically control generation of an output control signal indicating how the markup language representation is to be processed for generation of output based on the markup language representation. The markup processing program is applied in real-time to streaming XML data and represents logic instructions that carry out application of post processing such as XPATH expression evaluation, schema validation or other post processing on the stream of XML data.