2.1. SOAP and XML2.1.1. XML Messaging2.1.2. RPC and EDI2.1.3. The Need for a Standard Encoding2.2. SOAP Messages2.2.1. Envelopes2.2.2. RPC Messages2.2.3. The mustUnderstand Attribute2.2.4. Encoding Styles2.2.5. Versioning2.3. SOAP Faults2.3.1. Standard SOAP Fault Codes2.3.2. MustUnderstand Faults2.3.3. Custom Faults2.4. The SOAP Message Exchange Model2.4.1. Message Paths and Actors2.4.2. The SOAP Routing Protocol2.5. Using SOAP for RPC-Style Web Services2.5.1. Invoking Methods2.5.2. Returning Responses2.5.3. Reporting Errors2.6. SOAP's Data Encoding2.6.1. Understanding the Terminology2.6.2. XML Schemas and xsi:type2.7. SOAP Data Types2.7.1. Multiple References in XML-Encoded Data2.7.2. Structs, Arrays, and Other Compound Types2.7.3. Partially Transmitted Arrays and Sparse Arrays2.7.4. Null Accessors2.8. SOAP Transports2.8.1. SOAP over HTTP2.8.2. Contentious Issues