Integral Logistics Management — Operations Management and Supply Chain Management Within and Across Companies

20.2.3 Dimension Hierarchy Creation: Whole-Part Hierarchy, Specialization Hierarchy, Association Hierarchy

Intended learning outcomes: Differentiate between the component hierarchy, or whole-part hierarchy, and the specialization hierarchy. Explain the association hierarchy, or determination hierarchy.

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Through hierarchy creation, in a view of the information system, “lower” items belonging to a “higher” item are grouped/classified.

Hierarchy creation is a very important construct in modeling. It pervades and characterizes modeling, for which reason it can actually be called a dimension of modeling. Through hier­archy creation, elements belonging together are arranged, grouped, or classified in sets. The following three types of semantics in hierarchy creation are observed frequently in practice: 

  • Component hierarchy, or whole-part hierarchy
  • Specialization hierarchy
  • Association hierarchy, or determination hierarchy

In the component hierarchy, or whole–part hierarchy, a hierarchically superior element G is composed of (consists of) elements T1, T2, T3, …

In reverse order, each of the hierarchically subordinate elements T1, T2, T3, … is a part or component of a superior element G. Figure 20.2.3.1 illustrates the semantics.

Fig. 20.2.3.1       Component hierarchy, or whole–part hierarchy.

Examples of component hierarchies in the material world are:

  • A bicycle (as a whole) with its components: handlebars, frame, and wheels
  • A transport (as a whole) with its phases: load, transport, and unload.

Examples of component hierarchies in information systems are: 

  • A system with its subsystems
  • An object with its components
  • A process with its subprocesses
  • A function with its subfunctions
  • A task with its subtasks.

The dimension of the principle of proceeding “from the general to the particular” in systems engineering (Section 19.1.1) and in different modeling tool sets corresponds to a component hierarchy. 

In a specialization hierarchy the elements S1, S2, S3, … represent special manifestations of the superior element G. In other words, each of the elements S1, S2, S3, … is a (special) G.

In reverse order, the hierarchically superior element G is a generalization of all subordinate elements S1, S2, S3, … In other words, an element G can be an element S1 or an element S2 or an element S3, and so on. Figure 20.2.3.2 illustrates the semantics.

Fig. 20.2.3.2       Specialization hierarchy.

Examples of specialization hierarchies in the company environment are  

  • Employees of a company (generalization) with the various mani­festations “salaried employee,” “blue-collar worker,” and “trainee.”
  • A shipping service (generalization) with its various options: “express,” “normal,” or “lowest-cost” processing. 

Examples of specialization hierarchies in the modeling of information systems are

  • An object with its specialized manifestations
  • A process with various processing options

In an association hierarchy, or determination hierarchy, all elements G1, G2, G3, … that jointly define or determine a subordinate element A, or due to whose association an element A comes into existence or is generated, are placed superior to A.

In other words, to exist, element A needs all elements G1, G2, G3,… jointly. We can also say that A belongs to the elements G1, G2, G3, … together, or that A comes into existence because of their association. In reverse order, the hierar­chically superior elements G1, G2, G3,… jointly “generate,” “determine,” or “possess” a subordinate element A. Figure 20.2.3.3 illustrates the semantics.

Fig. 20.2.3.3       Association hierarchy, or determination hierarchy.

Examples of association hierarchies, or determination hierarchies, are:

  • To exist, a child needs a father and a mother. Or the child comes into existence by their association.
  • A taxpayer is defined by a person and a political unit (municipality)
  • A customer order is determined by a customer and a date.
  • Sales and distribution are determined by marketing (which is strategically superior) and long-term corporate planning.

Examples of association hierarchies in the modeling of information systems are: 

  • To exist, an object needs various other objects
  • A process is determined by several other processes 

The different verbs used to describe the semantics of the association hierarchy, point up different possible degrees of intensity of determination: from generation to possession. However, what they all always share is that the subordinate element cannot exist without the elements that determine it. The most intensive form is a “parent/child” relationship. 

The least binding form of the association hierarchy can be expressed by the verb “to have,” or in reverse order “belongs to.” However, the semantics are too general to characterize the association hierarchy, as it can also be used for the component hierarchy or for another hierarchical or nonhierarchical relationship. 

The various semantic constructs of creating hierarchies are recursive. Thus, multilevel constructs can be built:

  • Each component itself can in turn be composed of subordinate elements.
  • Each specialized element itself can in turn be specialized into further elements, possibly according to another criterion. 
  • Each element defined through a superior element can in turn, possibly together with further elements, determine a subordinate element. 

Familiar examples:

  • A bill of material or nomenclature is the structured list of components making up a product. It is a multilevel component hierarchy. See here also Section 1.2.2.
  • A classification system is a multilevel specialization hierarchy. An example of this is the German DIN 4000 standard, a standardized classification guide aiding the work of the designer, enabling the designer to systematically trace items — typically semiprocessed items and single parts. See here also Section 17.5.3.
  • The classical chain of command in a company or another human or mechanical organization is a multilevel determination hierarchy in which in each instance only one determining element has an influence on one subordinate element.
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Course section 20.2: Subsections and their intended learning outcomes

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