Onto-Med >> Theories >> GFO Part I Basic Principles

Overview

General Formal Ontology (GFO)

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• 16.1.1 Ontological Levels
• 16.1.2 Classes, Universals, and Individuals
• 16.1.3 Time and Space
• 16.1.4 Presentials, Persistants, and Endurants
• 16.1.5 Properties, Property Values, Qualities, and Qualia
• 16.1.6 Processes and Perdurants
• 16.1.7 Further Issues

16.1 Comparison to DOLCE

In this section we briefly discuss some similarities and differences between GFO and DOLCE. Figure 3 presents a tree of the DOLCE categories as shown in (39). In reference to that report, we omit a comprehensive introduction of DOLCE herein and discuss the basic distinctions in combination with the comparison, roughly following the order of the GFO elements presented in sections 4 to 13 . For an overview of DOLCE categories, refer to figure 3.

Figure 3: Taxonomy of Basic Categories in DOLCE (39, p. 14).

16.1.1 Ontological Levels

In DOLCE, levels of reality are not introduced explicitly. It seems that the levels are reflected in the DOLCE taxonomy of endurants, since physical, mental and social objects are distinguished therein. Here the question arises why the distinction between physical, mental and social entities is only embodied in the taxonomy of endurants, and is not present with respect to DOLCE perdurants and qualities. In GFO we explicitly distinguish three levels of reality, but we have not yet elaborated on levels for specific categories (cf. sect. 4).

16.1.2 Classes, Universals, and Individuals

DOLCE is an ontology of particulars. The root element of the DOLCE hierarchy is ``Particular'', understood to be an entity having no instances. This corresponds to our notion of an individual. Universals are mentioned in (39), but excluded from the ontology itself. Hence, we observe that DOLCE supports neither the distinctions provided in GFO concerning sets and items, nor concerning the typology of categories. However, it seems that our notion of set is similar to the DOLCE category ``Set'', which in DOLCE is only indicative. In the case of unary universals, DOLCE refers to the meta-ontology presented in (27).

16.1.3 Time and Space

GFO chronoids and space regions, respectively, can be reconstructed in the context of DOLCE as time intervals and space regions. However, time and space boundaries are not yet contained in DOLCE. Perhaps they can be integrated, but this should be examined carefully, because of the inclusion of time and space under qualities and qualia in DOLCE. It should also be stressed that the GFO approach to time is not equivalent to the common view of intervals composed of points. Rather, a novel solution has been presented in terms of the coincidence relationship (cf. sect. 5.1).

Moreover, in the case of material structures, we have introduced the notion of an individual quality called extension-space, related to a material structure by a specialized inherence relation. This may appear similar to the category of spatial location of DOLCE, but note that extension-space and the space occupied are completely distinct entities.

16.1.4 Presentials, Persistants, and Endurants

The notion of persistant refers to the idea of persistence through time as attributed to DOLCE's endurant. However, persistants are not considered in GFO as individuals but as universals. Accordingly, we assume that they do not change (directly), but rather that several of their instances, all of which belong to the category of presentials, can have different properties.

Presentials, on the other hand, can be generally interpreted as DOLCE endurants, but without temporal extension. They reflect the aspects of being wholly present at a time of their existence and being involved in processes (in GFO by being the projection of a process to a time-boundary). Hence we can interpret GFO material structures and material objects, respectively, as DOLCE physical endurants and physical objects (at a time-boundary). Material/physical objects in both ontologies satisfy the criterion of unity. Altogether, we can say that the DOLCE category of endurant can be reconstructed in GFO terms by using the categories of persistants and presentials, whereas the separation of these two aspects in GFO is prevented in DOLCE, since there are no universals.

DOLCE's deep taxonomy of endurants, especially concerning non-physical objects, is not yet covered by the GFO. Here two remarks seem relevant. First, at present the GFO is not meant to provide a deep taxonomy, neither of endurants nor of any other category. Second, we intend to solve the problem of social and mental entities in a systematic way, based on the theory of levels of reality.

16.1.5 Properties, Property Values, Qualities, and Qualia

The next question concerns interpreting DOLCE quales. On the one hand, they appear as GFO property values, since they may be shared among different particulars. But on the other hand, quales are positions of some quality in a quality space, where the latter is not considered to be universal but individual. Thus, the more difficult question is determing what a quality space in DOLCE is. We believe that the notion of a measurement system (cf. sect. 9.1) comes closest to quality spaces. Accordingly, quality spaces are interpreted as systems of property value universals in GFO. As a consequence, an interpretation of our individual property values is difficult in DOLCE. We have not found any DOLCE category that corresponds to individual property values.

Both ontologies provide the classification of properties with respect to the kind of entity which has the property (i.e., in which it directly inheres in the case of DOLCE). DOLCE distinguishes the categories of physical, temporal and abstract qualities, which directly inhere in physical structures, perdurants and abstracts, respectively. The GFO classification is only preliminary, but one can observe that the qualities of material structures correspond to DOLCE physical qualities, while abstract qualities are not distinguished in GFO. Moreover, we have not yet considered whether all properties of processes have the character of temporal properties. Neither DOLCE nor GFO consider properties of universals. In this regard, DOLCE refers to the meta-ontology in (27) and to the methodology OntoClean (26). Properties of universals are still a matter of debate in the case of GFO, also in connection with a refined typology of universals.

For properties, we can conclude that the DOLCE model of qualities may be reconstructed in GFO terms, but in the opposite direction, one cannot represent individual property values in DOLCE. On the other hand, GFO supports the DOLCE classification of qualities only partially.

16.1.6 Processes and Perdurants

DOLCE perdurants are introduced in contrast to endurants as entities that happen in time, are partially present in time, have temporal parts and cannot change in time. Intuitively, we can say that the notion of perdurant corresponds to our notion of occurrent. Moreover, it seems that the GFO notions of process, state and change can be interpreted in DOLCE as stative, state and event, respectively.

However, there are several differences. First, states and events are relative categories in the GFO, and there is an additional distinction between intrinsic and extrinsic changes. Secondly, the typologies of occurrents in GFO and of perdurants in DOLCE are not compatible. The typology of perdurants is based on the notions of homeomericity and cumulativity. In section 8.4 we discuss these notions and reject this way of classification for individual perdurants.

16.1.7 Further Issues

Apart from space and time boundaries, there are some other kinds of entities in GFO that are not easily interpretable in the current version of DOLCE. In particular, this refers to GFO relations and relators⁴¹, as well as to such entities like situations, configurations, situoids and configuroids. Facts are the only notion that is closely related to those mentioned and indicated in DOLCE.

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