This chapter discussed fundamental principles of modeling in information management. There exists no single and generally valid model for an operational information system. This is in accordance with the complexity of such sociotechnical systems. The goal is therefore to find a general framework in which the different conceptual models can be arranged and organized. To this purpose, three dimensions in the modeling of operational information systems were defined:
- Hierarchy creation, or the principle of proceeding from the general to the particular: This includes the component or whole-part hierarchy, the specialization hierarchy, and the association hierarchy or determination hierarchy.
- Four views in the modeling: Process view (sometimes also seen as control view), function view, object view (sometimes reduced to data view), and task or organization view.
- The phases of life of the information system: the concept phases preliminary study, main study, and detailed studies; system establishment (also called implementation); system introduction; system operation; and system disposal or decommission.
The basic design elements of data models and object models are object, attribute, and class, and in addition views of classes and the establishing of primary and secondary keys. From the user’s point of view, a class is a two-dimensional table, showing the attributes in the rows and the objects of a class in the columns. The different generations of design methods have resulted in different notations for objects, attributes, classes, views, and keys.
Classes, more precisely objects of classes, can be connected with each other in associations. Mostly, exactly two classes are in an association. Such a binary association can be described by two roles, each in one direction. A role, also called access function, is a statement on the type or basis of the association. An access function can be single-valued or multivalued. The maximum cardinality of an access function is the maximum number of objects or entities in the target class to which an object or entity of the initial class can lead. An access function can be total or partial. The minimum cardinality of an access function is the minimum number of objects in the target class to which each object of the initial class must lead.
If both roles, or access functions, of an association are single-valued, the association is said to be a 1-to-1 association. If at least one role is multi-valued, an association is said to be a 1-to-n association, or an n-to-1 association, or an n-to-n association. Each n-to-n association can be broken down into two 1-to-n associations, and that from each of the original class to a new class, which is called the association class. In some cases, this is naturally given, but in other cases it has to be postulated artificially. A possible primary key for the new class is always a combination of the primary keys of the two original classes. That kind of composite primary key can be replaced by a re-identification key.
The chapter also focuses attention on the breaking up of a reflexive n-to-n association. The relatively frequent occurrence of this construct is characteristic of operational information systems. Together with the other kinds of hierarchy creation, creating association classes is a powerful tool for the development of a company-wide generic data model or object model.
Course 20: Sections and their intended learning outcomes
Intended learning outcomes: Produce a review of important terms in information management. Disclose the modeling of operational information systems. Explain in detail the modeling of information systems in the data view and object view.
Intended learning outcomes: Produce definitions for terms from colloquial language that are easily understood by employees, such as for information, data, information technology, information system, database.
Intended learning outcomes: Present basic principles of modeling. Differentiate various dimensions in the modeling of information systems for business processes. Describe the dimension of hierarchy creation and the dimension of various views in modeling.
Intended learning outcomes: Present terms such as object, attribute, object class, view, primary and secondary keys. Explain basic concepts such as association, association role and type. Describe the breaking up of an n-to-n association – in particular a reflexive one – and the association class. Disclose the use of the hierarchical constructs for developing a company-wide generic object model.