our Specification Model describes describes Model Specification Operation describes Service describes Behaviour Object Behaviour Fig. 7.15 Information elements for property specification in service networks Resource Model Notation 7.3.1 Introduction A resource model, whether a service resource model or an object resource model, consists of up to seven sections, see Fig. 7.16. ResourceModelGraph Service refers Description Resource Model Rules isAspecification RefinementOf Resource PropertySpecification Model Object StateVector Resource StateModelSyntax Model Remark Fig. 7.16 Sections of a resource model As a general principle, AML distinguishes between notations for human readers and for machine interpretation. Only the former are regarded as mandatory infor- mation elements. In case of resource models, these are the resource model graph and the description. Remaining parts are optional or temporary information ele- ments, since they might not be needed for the purpose of the resource model. The resource model graph is absolutely essential, since the correct understand- ing of the service, and thereby of the operations and the behaviour depend on the graph. 7 Concepts and Notations for Process Control Systems Modelling The description is a natural language description of the resource model. It serves readers who are not familiar with the graphical notation, while at the same time (implicitly) explaining that notation. It is difficult (and sometimes impossible) to define all relevant relations graphi- cally in the resource model graph. Therefore, in general, it is better to list such relations (maybe all relations) separately in a rule section. Rules can be pre- sented as natural language statements, or by formal logical expressions. In the resource model graph, there is not much room for specifying properties which themselves are structures of properties, as well as values of properties. The property specification part is used to give such detailed information, if nec- essary. The state vector is a data model repr