Many ontology-development tools allow users to supplement frame-based representations with arbitrary logical sentences. However, few users actually take advantage of this opportunity. For example, in the Ontolingua ontology library, only 20% of the ontologies have any user-defined axioms. We believe the difficulty of composing axioms primarily accounts for the lack of axioms in these knowledge bases: Many domain experts cannot translate their thoughts into abstract and symbolic representations. We attempt to remedy the difficulties by identifying groups of axioms that manifest common patterns, creating “templates” that allow users to compose axioms by “filling in the blanks.” We studied axioms in two public ontology libraries, and derived 20 templates that cover 85% of all the user-defined axioms. We describe our methodology for identifying the templates and present examples. We constructed an interface that allows users to create constraints on knowledge bases by “filling in blanks;” our usability testing shows that users could use templates to encode axioms with a success rate similar to that of experts writing directly in an axiom language. Our approach should foster the introduction of axioms and constraints that are currently missing in many ontologies.
