KKO Upper Structure

The upper structure of the KBpedia Knowledge Ontology (KKO) is informed by the triadic logic and universal categories of Charles Sanders Peirce. This trichotomy, also the basis for his views on semiosis (or the nature of signs), was in Peirce's view the most primitive or reduced manner by which to understand and categorize things, concepts and ideas (discussed further below the table).

Here is the upper structure of KKO with its 171 concepts:

The three constituents of Peirce's trichotomy, which are keyed into the table entries above, are what he called simply the Three Categories, or the universal categories. These three categories can be roughly summarized as:

• Firstness [1ns] — these are possibilities or potentials, the basic forces or qualities that combine together or interact in various ways to enable the real things we perceive in the world, such as matter, life and ideas. These are the unrealized building blocks, or elements, the essences or attributes or possible juxtapositions. The are not divisible, what Peirce called indecomposables, since they are integral qualities or ideas in themselves
• Secondness [2ns] — these are the particular realized things or concepts in the world, what we can perceive, point to and describe. As instantiated, they are actuals. A particular is also known as an event, entity, instance or individual
• Thirdness [3ns] — these are the laws, habits, regularities and continuities that may be generalized from particulars or possibilities. All generals — what are also known as classes, kinds or types — belong to this category. The process of finding and deriving these generalities also leads to new insights or emergent properties, which continue to fuel knowledge discovery. Insights arising from Thirdness enable us to further explore and understand things, and is a driving force for further categorization.

Understanding, inquiry and knowledge require this irreducible structure. Connections, meaning and communication depend on all three components, standing in relation to one another and subject to interpretation by multiple agents. (Traditional classification schemes more often have a dyadic or dichotomous nature, which does not support the richer views of context and interpretation inherent in the Peircean view.)

Of course, some Peircean scholars may rightfully see these explanations as a bit of a cartoon, and a possible injustice to his lifetime of work. For more than 100 years philosophers and logicians have tried to plumb Peirce's insights and writings. But we can apply his triadic logic to achieve a logical, coherent approach to categorization and knowledge representation.

Peirce argues persuasively that how we perceive and communicate things requires this irreducible triadic structure. The symbolic nature of Thirdness means that communication and understanding is a continuous process of refinement, getting us closer to the truth, but never fully achieving it. Thirdness includes a social and imprecise mode of communication and discovery, conducted by us and other agents separate from the things and phenomena being observed. Though it is a fallibilistic process, it is one that also lends itself to rigor and methods, in a constant quest for truth. The scientific method is a premier example of Thirdness in action.

What constitutes the potentials, realized particulars, and generalizations that may be drawn from a query or investigation is contextual in nature. That is why the mindset of Peirce's triadic logic is a powerful guide to how to think about and organize the things and ideas in our world. It provides a universal context for relating different knowledge bases and sources of information to one another, which is the express purpose of KKO. Peirce's triadic logic and views on categorization are fractal in nature. We can apply this triadic logic to any level of information granularity.

Thus, KKO applies this mindset to organizing its knowledge graph. At each level in the KKO upper structure, we strive to organize each category according to the ideas of Firstness (1ns), Secondness (2ns) and Thirdness (3ns), as shown in the simplified KKO tree above. Also note that most of the reference concepts (RCs) in KKO are organized under the Generals (3ns) branch. A type is an embodiment of a general, and that is why all of KKO's SuperTypes (typologies) reside there.

The KKO upper structure may be downloaded and inspected in greater detail. Use the non-working kko-demo.n3 file if you wish to see the linkage to the universal categories in your ontology browser. Periodic discussions of Peirce and the KKO structure may be found on Mike Bergman's blog.