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modeling_of_activities_and_processes

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Occurrences, activities, processes and events

An occurrence is in its widest sense anything that happens. This includes human activities, but also physical and (bio)chemical processes, control processes, events and physical phenomena. Processes includes both discrete processes and continuous processes. A discrete process consists of a sequence of discrete process steps or actions. Examples of discrete processes are business processes in which various persons provide a contribution in the process, mechanical production processes in the mechanical industry and batch processes in the chemical industry. A continuous process is a process that is an operation on a continuous stream of raw material to produce one or more continuous streams of product materials. Examples of continuous processes are the flowing of water in a river, the operation of an electric power generation plant and the various refinery processes. An occurrence in fact always happens over time, but in some cases, such as events, the duration can be neglected. All these kinds of occurrences can be modeled in Gellish in a similar way.

1. Classification of occurrences

Occurrences, and its subtypes: activities, processes and events, can be classified by kinds of occurrences, whereas the names of those kinds consists either of nouns or of verbs. For example, a particular individual human activity can be classified as a 'walk' or as 'walking'. Both kinds of terms are considered as being equivalent denotations of the same kind of occurrence. Therefore both such terms are included in the Gellish Dictionary as synonyms. Kinds of occurrences can be denoted by terms in an active form, a passive form and a noun form and sometimes other forms. For example: act, acting and action, but also activity. All such forms are treated as synonyms in Gellish.
Each individual activity, process or event shall be classified explicitly, for example as follows:

UID of left hand objectName of left hand objectUID of ideaUID of kind of relationName of kind of relationUID of right hand objectName of right hand object
1 compr-1 101 1225 is classified as a 191936 compression

An occurrence, activity, process or event is further specified by describing the kinds of behavior of the objects that are involved in the occurrence, as well as their mutual interaction. This means that an occurrence is an interaction between two or more objects. Thus more than two objects can be related because of their participation in one occurrence. It is even possible that a variable number of objects are involved over time in one occurrence. For example in a project or a meeting. The modeling of occurrences therefore requires that it should be possible that more than two objects are involved in one occurrence. This can be achieved in Gellish by modeling occurrences as 'objects' that represent higher order (or variable order) relations, being relations with typically more than two related objects. The details of an occurrence are expressed by the specification of the objects that are involved in the interaction, especially in the various roles that they play.

2. Specification of how objects are involved in occurrences

An occurrence is modeled as a higher order relation, because an occurrence is an interaction of several objects. This means that several objects are involved in an occurrence, each with its own role, although often only the involvement of one or two objects with their roles are specified. The roles that various objects play in an occurrence are modeled in Gellish by the specification of a different expressions for each involved object. Each of such an expression specifies that an object plays a particular role in the occurrence. This results in several lines with involvement relations. The involvement relations are described by expressions that use kinds of relations that are subtypes of the <is involved in> relation type.
For example:

Name of left hand objectName of kind of relationName of right hand object
fluid-1 is input in heat transfer-1

The Gellish English Dictionary contains a large number of kinds of involvement relations that describe ways in which objects can be involved in occurrences, processes and activities. For example:

  • is performer of
  • is enabler of
  • is input in
  • is output of
  • is subject in
  • is tool in
  • is enabler of
  • is controlled by
  • etc.

If only the two roles are of interest, the roles of a performer and of a subject, then it is allowed in Gellish to express the occurrence as a binary relation. For example, the idea: 'pump P-101 pumps fluid S-1' can be expressed as follows:

UID of left hand objectName of left hand objectUID of ideaUID of kind of relationName of kind of relationUID of right hand objectName of right hand object
1 P-101 101 194201 pumping 2 S-1

The UID of the idea (in the example idea 101) is the identifier of the occurrence. In this example the individual occurrence is not given a name. However, as a guideline it is recommended that software generates a name that is the concatenation of the name of the kind of relation, the word 'of' and the name of the individual subject. In the example the name of the process would be ‘pumping of S-1’.

3. Definition of kinds of occurrences, activities, processes and events

Occurrences that do not exist yet in the Gellish English dictionary can be added in a similar way as defining physical objectsby obeying the [wiki:“Proper definition of a concept” rules for proper definitions] in Gellish English. A kind of occurrence shall be defined as a subtype of an existing kind of occurrence and facts that are by definition true shall be added to complete the definition.
In general, generic kinds of activities and processes are independent of the subject of the occurrence, and independent of the performer or the enabler. For example, the activity 'design' or 'operate' does not include an indication of what is designed or operated. However, more specialised ‘qualified’ activities often do include the subject of the activity or process. For example, “design a pump” or “operate a facility”. In such a case the definition of such a kind of occurrence should include and explicit relation that states that it has by definition as subject a particular kind of thing. For example:

Name of left hand objectName of relation typeName of right hand object
design a pump is a qualification of design
design a pump has by definition as subject a pump

Similar considerations apply for specific activities that include a specific subject. For example, the specific activity called 'design P-101“ is by definition a design of a thing called P-101. This is specified as follows:

Name of left hand objectName of relation typeName of right hand object
design of P-101 is classified as a
design of P-101 has as subject

4. Specification of activity sequences

Often it is required to specify in which sequence activities or chains of shall be or are performed. This may result in activity networks. For example, in activity scheduling for testing, commissioning and start up of facilities or to describe a maintenance procedure. This can be done for sequences of kinds of activities, but also for sequences individual activities, or for procuderes in which typical activity sequence is describedthat shall be repeated every time that the procedure is followed.
For example, the following activity sequence may describe steps that shall be taken during a planned maintenance shut-down (also called a turnaround) of facility:

Name of left hand objectName of relation typeName of right hand object
purge a vessel shall occurs after a drain a vessel
inspect a vessel shall occurs after a purge a vessel

Whereas a sequence of individual activities is expressed as follows:

Name of left hand objectName of relation typeName of right hand object
assemble system A occurs after clean system A
test system A occurs after assemble system A

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modeling_of_activities_and_processes.1541076426.txt.gz · Last modified: 2018/11/01 13:47 by andries