rPress and used by DyeRun Controller *optimalTemp service object service relation *powerLev *expTime getREQ putORD Temp. setTempREQ Contr. Setup inititRunREQ DyeRun Agent Controller f1..f7 fillSolREQ Process Level tankEmptyC_REP Operator Contr. runREQ Release startTimingORD Timer timeOutC REP startORD Controll. relPressoRD Press. Contr. setPressORD Fig. 6.3 A service network; this network describes a PCS that controls a fabric-dying process When considering implementation and P- and D-dimension aspects, service objects need to be aggregated in the same abstract machine. This is an integration task, since the abstract machine must then implement an access mechanism SO that individual service objects can be accessed from other abstract machines. An exam- ple is given in Fig. 6.4 that shows part of a possible abstract network for integrating the service network of Fig. 6.3. The object handler is the integration mechanism that provides some extra access operations (here seizeServRelREQ and relServRe- IORD) for process operators. abstract machines object abstract protocol Setup DyeRun Agent Controller Process seizeServReIREQ Operator Object relServRelORD Handler (OBH) Fig. 6.4 Part of the abstract network for the service network of the fabric-dying control system A service network specifies two things: a (functional) structure (i.e. how the function is modularized in terms of interacting service objects) and the behaviour 6.2 A Service Network Modelling Case of the function. The structure depends basically on how the data that describe the RS are partitioned. The behaviour of the service network is defined by the behav- iour of the service objects. Service objects are small state machines that interact with other service objects by means of instances of ASPs that refer to operations. Most service objects control their own behaviour through their object state, consid- ering all service relations an object handles. The state of an object is a function of the state of the resource system model, and of the structure of th