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A complete set of descriptors

Atomic descriptors

In the following, the assets will be considered as placeholders for the asset values. A task is a placeholder for its priority. A task is also characterized by a program and by a target. The program consists of operators or operations that are more complex, local assets and path selectors. Together the assets, the atomic sub-states, the task priorities, the task scheduling criteria, the distribution of tasks over the available threads, the operators, the state transitions and the triggers constitute a complete view of the observed dynamic system.


Atomic specification element


Unstructured Asset

Place holder for asset value

Atomic sub-state

Value of an unstructured asset

Atomic operand

Indivisible operation


Priority of a task

State transition

Experience of occurrence in which one state transfers into another

Atomic path selector

Decides on Boolean asset value

Operand statement

Triggers an operand or a more complex operation

Schedule trigger

The criterion for a single scheduling action


The appearance of a subject, the content of a resource and the target of a task are complex concepts that often have no precise description. However, directly or indirectly, any description of these items will use the above atomic descriptors.

The program block separators are examples of administrative descriptors. Administrative descriptors define how other parts of the description must be used. The name of a method result is another kind of administrative descriptor.

If the system is modeled and implemented in software, the implementation itself may introduce some extra independent descriptors. This will be treated later, but the distribution of tasks over threads and the name of the method result are examples of extra descriptors.

Categorization and grouping

By categorizing the atomic descriptors and by grouping descriptors in subgroups that appear to occur frequently in different circumstances, the handling of the descriptors can be simplified or familiarized.

Examples are the categorization of assets that are placeholders of properties as ‘attributes’ and the categorization of a sequence of state transitions that belong to one action as an ‘operation’. A method is a combination of an operation and the parameters that are transmitted. The operation is controlled by a program. In software, the method also encompasses the method result and the state-transition in the original sender that is caused by the callback. A group of methods that regularly occur together is often combined in an ‘interface’. Contrary to the atomic descriptions, the groups do not have to be independent. For example, a method may appear in more than one interface. Attributes and parameters are placeholders for the values of assets. Relations are a special kind of assets. An attribute or parameter that represents a relation is called a ‘reference’.

Equivalence Classes

Higher-level specifications that occur frequently will be used as higher-level design elements. The realizations of higher-level design elements form equivalence classes. Often, an equivalence class can be derived from another class. The instances of the derived class can also be interpreted as instances of the parent class.

Grouping can be used to reduce complexity. Potential relations are the source of complexity. If a group is always referred to as a whole, then the number of potential relations is effectively reduced. Another way to reduce complexity is the encapsulation of a set of subjects into a module, such that the values of the assets can only be accessed through interfaces. In this way, the module can be made responsible for its own behavior. Usually these modules can also be grouped in equivalence classes.

Equivalence classes can often be seen as a specialization of other classes. This leads to a hierarchy or even a network of equivalence classes. Part of the specification of the child class coincides with the specification of the parent class. This may be used to increase specification efficiency. Grouping in equivalence classes has so many advantages that often, even in case of singletons, the concept of equivalence class is used.

An instance of an equivalence class is the actual realization of a class member. Instances of these classes will be identified with two identifiers; a class-related identifier and an instance-related identifier. Sometimes a globally unique identifier is used in parallel with the class-related identifier.


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