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Introduction to Ontology

This guide provides a foundational understanding of ontology and its key concepts, particularly focusing on the Basic Formal Ontology (BFO) framework.

Defining Ontology​

An ontology is a representation of some part of reality, (e.g. medicine, social reality, physics, etc.). Smith states that: “Ontology is the science of what is, of the kinds and structures of objects, properties, events, processes and relations in every area of reality…Ontology seeks to provide a definitive and exhaustive classification of entities in all spheres of being.” To be an accurate representation of reality an ontology includes the types of entities and events in a given domain (along with their definitions) arranged in a hierarchical structure, along with relations (such as part-of, depends-on, caused-by, etc. where necessary). Ontologies enable the formulation of robust and shareable descriptions of a given domain by providing a common controlled vocabulary for doctrine writers, IT Developers, and war-fighters alike, thereby allowing these disparate communities to communicate with each other. An ontology should be a shared resource between communities, and its continued collaborative development should support the integration of information and facilitate knowledge discovery. These two goals are realized by ensuring wide dissemination of the ontology, so that it will be used by many stakeholders, and its terms will be correspondingly familiar and readily used for search.

Core Concepts​

Basic Formal Ontology (BFO)​

BFO is a top-level ontology that provides a framework for organizing and categorizing entities in the world. Key concepts include:

  • Stasis: The state of being static or unchanging
  • Process Profile: A pattern of processes that occur over time
  • Process Characteristic: The counterpart of 'quality' for processes
  • Capability: A disposition whose realizations satisfy interests of organisms or groups
  • System: An object aggregate whose members interact

Systems​

A system is defined as:

  • An object aggregate whose members interact
  • Members are called "elements" of the system
  • Interaction occurs when objects participate in the same process
  • Systems can be elements of higher-order systems

Key Principles​

Realism and Top-Level Ontology​

  • Based on philosophical realism
  • Uses a hub-spokes approach to ontology development
  • Distinguishes between universals and instances

Language and Naming​

  • Uses singular nouns for entities
  • Incorporates mass nouns appropriately
  • References material entities (see Wikipedia)

Dependencies and Relationships​

  • Specific dependence
  • Generic dependence (GDC, ICE)
  • Copyable patterns and concretizations
  • Dispositions and qualities
  • Capabilities and functions

Quality Layers​

Qualities can have multiple layers (e.g., colored vs. red)

Ontological Rules​

  1. The all-some rule
  2. Single inheritance principle
  3. Aristotle's definition of substance rule
  4. Universal quantification rule
  5. No multiple inheritance (asserted vs. inferred)

Tools and Resources​

Definitions and Axioms​

In first-order logic, definitions and axioms must be kept separate:

  • Definitions provide the shortest, logically simplest specification of necessary and sufficient conditions
  • Axioms specify additional distinguishing marks for all instances
  • This separation provides:
    1. Easy understanding and application of definitions
    2. Stability as new kinds of entities are discovered or evolve