A general problem with computer science terminology is that some terms are often used for different concepts and that the same concepts are denoted by different terms. To a great extent, this is due to the rapid advances in computer science where new concepts need new names.
We illustrate these issues by means of a special section in the August 1997 Communications that focused on the practical application and uses of health care information systems. These articles revealed some confusion with terminology in the area. For example, in one of the articles, a hospital information system is regarded as a particular type of product that only focuses on patient registration, admission, discharge, transfer, and other administrative functions, whereas a clinical information system is regarded as a product that focuses on physicians’ use [1]. A personal communication with the author made clear that many hospital information systems contain both administrative and clinical components. However, reading this article, one can get the impression that hospital information systems and clinical information systems are regarded as disjoint systems. It is not so unusual for the term “hospital information system” to be used with this restricted functionality in mind (in particular by the hospital information systems vendors), despite the fact that the more appropriate term, “hospital administration system,” was introduced more than 20 years ago [6].
Saying a hospital information system contains a clinical information system is more appropriate; the term “hospital information system” should denote a broader concept of an information system for the hospital as a whole (which usually includes administrative and clinical components). Furthermore, a hospital information system is a kind of health care information system.
Some Problem-Solving Efforts
Collen [3] presents an early classification for a subdomain of computer science, namely medical information systems. This taxonomy distinguishes between a hospital information system and an office information system as being parts of a medical information system, whereby both hospital information systems and office information systems contain an administration system and a clinical information system. This redundancy seems unnecessary and not very intuitive since many functions offered by both contained administration systems are identical.
More than 250 terms were candidates for a European standard that defines a Medical Informatics Vocabulary (MIVoc) [2]. Different than Collen’s taxonomy, the terms are organized into a generalization/specialization hierarchy (plus some additional links specified textually within a glossary). However, the final European standard defines and organizes only 59 of these terms into the tree structure, whereby only the 27 leaf nodes are defined in the core list of entries [2]. The remaining candidate terms are listed alphabetically in an appendix without being given detailed definitions. In particular, the varieties of information systems classified in the accompanying box are only listed in the appendix of the standard and not classified within the tree structure.
An Object-Oriented Taxonomy for Health Care Information Systems
We propose systematizing the terminology by means of taxonomies and employing an object-oriented modeling notation to specify the taxonomy. As an example, the figure displays a taxonomy for health care information systems that has been modeled using the Unified Modeling Language (UML) notation for class diagrams [4]. The taxonomy provides a coarse classification of the functional requirements on such systems, not a decomposition into technical subsystems. This taxonomy is based on textbooks for medical informatics. The individual elements and the notation in the figure are explained in the figure box.
Logical Components vs. Physical Subsystems
The taxonomy presented corresponds to an assignment of functionality to specific functional components. In a particular setting, one such logical component may be realized through multiple physical systems, or one physical system may realize multiple logical components. The resulting requirements on system integration are not the subject of the taxonomy, which addresses the logical distribution of functionality. However, the dependencies and required integration would be relevant for the actual implementation of a health care information system. For instance, access to computer-based patient records will be required by the other components of a hospital information system or by a telemedicine system (in our taxonomy, it is not explicit that some components may require access to each other). The overlapping areas of data among the components of a hospital information system are not modeled because this is not relevant for a taxonomy that classifies functionality. Refer to [5] for discussions of some problems and solutions to the integration of heterogeneous subsystems within a hospital environment.
Summary
We have shown how an object-oriented modeling notation can be used to present a taxonomy. The simple classification for medical information systems in [3] uses only aggregation, and the medical informatics vocabulary in [2] primarily uses a generalization/specialization hierarchy to relate terms to each other. The object-oriented modeling notation of the UML allows both generalization/specialization and aggregation/composition to be specified within a taxonomy in a visual way. To some extent, the presented taxonomy reflects our view on the domain, but it is based on previous research and on textbooks for medical informatics. Exemplary, a simple taxonomy for a small domain, namely health care information systems, is presented to illustrate the ideas. An important concern is the visual specification of the relationships among the defined terms.
Our central claims are:
- Systematizing the terminology in computer science by means of taxonomies is useful.
- Employing an object-oriented modeling notation to present the taxonomies is appropriate.
We consider such taxonomies important steps toward overcoming existing confusion with terminology in the area. Often, terminology is a problem for computer science because the development is so fast that people frequently use the same terms for different concepts or different terms for the same concept. A systematic terminology is useful to solve some of the resulting problems.
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