15. A method of validating a message received by an intermediate computer in a communication network, comprising the following steps: acquiring the message, at the intermediate computer, from a service description document comprising a description of a processing functionality implemented during a preprocessing or the post-processing of data in XML format of the message exchanged during the execution of a service on the communication network; extracting, from the service description document, the description of a service associated with the document; extracting a processing from the received message; acquiring from said service description document at least one imperative value associated with a property of the processing; verifying whether said imperative value is included in a list of values which can be attributed to a property supported by said processing functionality described in the service description document; reading a value associated with a property adapted to specify whether the processing is executed before or after the sending of said message; executing said processing when said read value specifies that the processing must be executed before the sending of the message; and validating the result of said processing with respect to a type of data specified in said service description document.
15. A method of validating a message received by an intermediate computer in a communication network, comprising the following steps: acquiring the message, at the intermediate computer, from a service description document comprising a description of a processing functionality implemented during a preprocessing or the post-processing of data in XML format of the message exchanged during the execution of a service on the communication network; extracting, from the service description document, the description of a service associated with the document; extracting a processing from the received message; acquiring from said service description document at least one imperative value associated with a property of the processing; verifying whether said imperative value is included in a list of values which can be attributed to a property supported by said processing functionality described in the service description document; reading a value associated with a property adapted to specify whether the processing is executed before or after the sending of said message; executing said processing when said read value specifies that the processing must be executed before the sending of the message; and validating the result of said processing with respect to a type of data specified in said service description document. 17. A computer-readable storage medium on which is stored a computer executable program to implement the method of validating a message according to claim 15 .