 type: the primitive types occurring in Fig. 7.24 are Request, Con- firm and Refuse (shortened to Req, Cnf and Ref respectively). There are six other possible values, see the diagram in Fig. 7.22. Primitive type values are defined as part of AML. A primitive type value has a specific position in the dia- logue between user and provider, and defines which of the provider and user is the initiating party. Primitive type values are grouped according to the operation classification system of AML, see Sect. 7.4.4. The parameter set: each communication event carries a set of values from a parameter set that is unique for each combination of operation names and primi- tive types. The values that occur in Fig. 7.24 are 12 (a value of the parameter time) and watchBroken (a value of the parameter cause). Note that the parame- ter set may be empty for some communication events (as for the event timeRe- quest). Note that a communication event expresses the initiating party's meaning with the communication, but says nothing about how that meaning is made known to the detector. Obviously, between initiation and detection, the event must be repre- sented as data (part of messages between the protocol elements in which the objects are allocated). That data must then be transported between the objects, which requires connectivity services, etc. This process is, however, completely dis- 7 Concepts and Notations for Process Control Systems Modelling regarded in service network modelling, and in abstract network modelling as well. A service or object behaviour therefore comprises properties that are quite different from message protocols, and are very attractive to the service network modeller: There is no time delay to consider between initiation and detection. Don't con- fuse this with the fact that the detector may delay the execution of the operation that is referred, and that the execution itself takes time. These are properties that are specified in the operation specification, see Sect. 7.4.5. There is no corruption of data t