next up previous
Next: Type-level and instance Up: Process Modelling in Previous: Basic EPOS-PM Concepts

SPELL

SPELL stands for Software Process Evo Lutionary Language [C+92] [COWL91]. It is the Process Modelling Language of EPOS. It allows to model the three classes of process entities just presented (i.e. activities, products and relations).
SPELL conforms to the Object-Oriented paradigm. A task, for example, can model many different kinds of activities: the compilation of a source module as well as an high-level ``testing'' activity. The corresponding modelling types are the subtypes of a common TaskEntity root type. Quite similarly, a source code module and a design document have a common DataEntity ancestor which contains the set of common properties.
Figure 1.4 shows some system-defined and predefined types.

  
Figure 1.4: Part of the EPOS type hierarchy.

Entity is a system-defined root type. It has two subtypes:

Meta-types can be described as ``the type of the types'', in that normal types are instances of them. From a practical point of view, meta-types can be handled as any other type in EPOS and could theoretically be used to model different domains of application of the system, i.e. by providing EPOS with domain knowledge. Meta-types can be refined through subtyping, but this does not mean that every type possesses its own meta-type (the default semantics when a new type is created, is to have it ``inherit'' the meta-type of its super-type). PM_Entity is the class gif of any process element, and only acts as a container of the two basic types TaskEntity and DataEntity. The meta-types of these two are TaskDescriptor and DataDescriptor, which are, in practice, also the meta-types of all the subtypes of the two types just mentioned.

Before we provide a more detailed view of SPELL,we must clarify the inheritance mechanism exploited by EPOS and the difference between type-level and instance-level attributes. To these subjects we dedicate the next two paragraphs.





next up previous
Next: Type-level and instance Up: Process Modelling in Previous: Basic EPOS-PM Concepts



Passani Luca
Mon Feb 20 21:59:27 MET 1995