Chart showing the relation between a conceptualization in information science, its various ontologies (each with its own specialized language), and their shared ontological commitment.
In information science a conceptualization is an abstract simplified view of some selected part of the world, containing the objects, concepts, and other entities that are presumed of interest for some particular purpose and the relationships between them. An explicit specification of a conceptualization is an ontology, and it may occur that a conceptualization can be realized by several distinct ontologies. An ontological commitment in describing ontological comparisons is taken to refer to that subset of elements of an ontology shared with all the others. "An ontology is language-dependent", its objects and interrelations described within the language it uses, while a conceptualization is always the same, more general, its concepts existing "independently of the language used to describe it". The relation between these terms is shown in the figure to the right.
Not all workers in knowledge engineering use the term ‘conceptualization’, but instead refer to the conceptualization itself, or to the ontological commitment of all its realizations, as an overarching ontology.
As a higher level abstraction, a conceptualization facilitates the discussion and comparison of its various ontologies, facilitating knowledge sharing and reuse. Each ontology based upon the same overarching conceptualization maps the conceptualization into specific elements and their relationships.
The question then arises as to how to describe the 'conceptualization' in terms that can encompass multiple ontologies. This issue has been called the 'Tower of Babel' problem, that is, how can persons used to one ontology talk with others using a different ontology? This problem is easily grasped, but a general resolution is not at hand. It can be a 'bottom-up' or a 'top-down' approach, or something in between.
However, in more artificial situations, such as information systems, the idea of a 'conceptualization' and the 'ontological commitment' of various ontologies that realize the 'conceptualization' is possible. The formation of a conceptualization and its ontologies involves these steps:
specification of the conceptualization
ontology concepts: every definition involves the definitions of other terms
relationships between the concepts: this step maps conceptual relationships onto the ontology structure
groups of concepts: this step may lead to the creation of sub-ontologies
formal description of ontology commitments, for example, to make them computer readable
An example of moving conception into a language leading to a variety of ontologies is the expression of a process in pseudocode (a strictly structured form of ordinary language) leading to implementation in several different formal computer languages like Lisp or Fortran. The pseudocode makes it easier to understand the instructions and compare implementations, but the formal languages make possible the compilation of the ideas as computer instructions.
Another example is mathematics, where a very general formulation (the analog of a conceptualization) is illustrated with 'applications' that are more specialized examples. For instance, aspects of a function space can be illustrated using a vector space or a topological space that introduce interpretations of the 'elements' of the conceptualization and additional relationships between them but preserve the connections required in the function space.
The ontological commitments of a theory are those things which occur in all the ontologies of that theory. To explain further, the ontology of a theory consists of the objects the theory makes use of. A dependence of a theory upon an object is indicated if the theory fails when the object is omitted. However, the ontology of a theory is not necessarily unique. A theory is ontologically committed to an object only if that object occurs in all the ontologies of that theory. A theory also can be ontologically committed to a class of objects if that class is populated (not necessarily by the same objects) in all its ontologies. [italics added]
“Researchers...come from different areas of study and have different perspectives on modeling, but significantly they pledged to adopt the same ontological commitment. That is, they agree to adopt common, predefined ontologies...to express general categories, even if they do not completely agree on the modeling behind the ontological representations. Where ontological commitment is lacking, it is difficult to converse clearly about a domain and to benefit from knowledge representations developed by others... Ontological commitment is thus an integral aspect of ontological engineering.” [italics added]
^In information science, one approach to finding a conceptualization (or avoiding it and using an automated comparison) is called 'ontology alignment' or 'ontology matching'. See for example, Jérôme. Euzenat, Pavel Shvaiko (2007). Ontology Matching. Springer. ISBN3540496122.