Adaptive SOAP (A-SOAP) is a practical approach to SOAP message compression. A-SOAP separates mechanisms from policies and allows for incremental deployment. This paper focuses on its three underlying mechanisms: accelerating message composition, reducing parsing overheads, and compressing messages, which leverages the previous two mechanisms. In contrast to existing dictionary-based compression techniques, ASOAP does not require dictionaries to be exchanged between the two endpoints in advance; its dictionaries are built incrementally, as the communication progresses. ASOAP endpoints agree on the dictionary management policy using a mechanism similar to HTTP content negotiation, possibly using a dedicated HTTP header field. In experiments with short messages and a simple policy, an A-SOAP prototype reduces processing overheads by half and message sizes by an order of magnitude without increasing message latencies.