Pragmatics of the Knowledge Level

new hypotheis test observable new evidence abstract finding focus trigger specific finding FIGURE 5.11: Introducing nding abstractions In addition, syndromatic abstraction could be considered as a fourth type of abstraction. In syndromatic abstraction, a cluster of ndings is treated as one aggregate nding. Clustering of ndings is probably the most e cient way of limiting the number of hypotheses in the di erential. For example, the combination of physical stress and retro-sternal pain triggers the hypothesis angina pectoris. Retro-sternal pain in isolation would generate all ischaemic heart diseases and possibly some additional ones as well. These four types of abstraction can be seen as a special type of di erentiation of the abstract inference, which we have called inference di erentiation (cf. Sec. 5.3). In this case, abstract can be di erentiated into four sub-inferences, based on the type of domain knowledge used by the inferences (see Fig. 5.12). Finding abstractions Operation Addition of knowledge source Addition of specialised role (\abstract nding") Method Knowledge di erentiation Criteria Computational Chapter 5. Model Construction 89