In environments with limited network bandwidth or resource-constrained computing devices the high amount of protocol overhead caused by SOAP is disadvantageous. Therefore, recent research work concentrated on more compact, binary representations of XML data. However, due to the special characteristics of SOAP communication most of these approaches are not applicable in the field of web services. First, we give a detailed overview of the latest developments in the field of XML data compression. Then we will introduce a new approach for compressing SOAP data which utilizes information on the structure of the data from an XML Schema or WSDL document to generate a single custom pushdown automaton. This cannot only be used as a highly efficient validating parser but also as a compressor: its transitions are tagged with short binary identifiers which replace XML tags during compression. This approach leads to extremely compact data representations as well as low memory and CPU utilization.