Introduction & Philosophy

What is DUL?

DUL (DOLCE+DnS Ultralite) is a foundational ontology designed to provide reusable, domain-independent patterns for modeling any domain of discourse. It represents a simplification and practical adaptation of DOLCE (Descriptive Ontology for Linguistic and Cognitive Engineering), one of the most influential foundational ontologies in knowledge representation.

Key characteristics:

Pattern-based architecture: DUL is not just a taxonomy, but a collection of content ontology design patterns (ODPs)
Lightweight yet foundational: Easier to apply than full DOLCE while maintaining philosophical rigor
Domain-agnostic: Designed to work across physical, social, and mental domains
Epistemologically committed: Recognizes that our knowledge is framed by descriptions and contexts

Origins

DUL emerged from the Ontology Design Patterns (ODP) initiative, which recognized that ontology engineering benefits from reusable conceptual patterns, similar to design patterns in software engineering.

From DOLCE to DUL:

DOLCE Lite-Plus: The parent ontology, grounded in formal ontology and philosophical analysis
Simplification goals: Make names more intuitive, relax some formal constraints, focus on practical applicability
Integration of D&S: Incorporates the Descriptions and Situations (D&S) pattern as a core architectural principle

Core Ontological Commitments

DUL makes several fundamental commitments about reality and how we model it:

Descriptive vs. Prescriptive

DUL is descriptive: it aims to model how people actually conceptualize reality, not to prescribe a single "correct" ontology. This philosophical stance acknowledges ontological pluralism—different communities and contexts may legitimately organize reality differently.

The Frame-Based View

Reality is always understood through conceptual frames (Descriptions). We never access "raw reality" but always reality-as-interpreted. This echoes:

Kant's epistemology: We know phenomena (appearances) through mental categories, not noumena (things-in-themselves)
Frame semantics (Fillmore): Concepts are understood within structured mental frames
Constructivism: Social reality is constructed through shared conceptualizations

Multiple Perspectives

The same entity can be validly viewed from multiple perspectives:

An event can be seen as an accomplishment, achievement, process, or state transition
A physical object can be a designed artifact, a biological object, or a refunctionalized entity
These are not different identities but different Situations that frame the same entity according to different Descriptions

Reification Strategy

DUL heavily uses reification—turning relations and attributes into first-class entities:

Qualities: Instead of direct attributes, DUL reifies qualities (e.g., "the yellowness of Dmitri's skin")
Regions: Values are abstract regions in dimensional spaces (e.g., specific colors in color space)
Situations: Relations are reified as situations (e.g., "John being a student in 2024" is a situation)

This enables:

Time-indexing: "John was a student in 2020 but is now a teacher"
Context-sensitivity: "This object is a cradle in the baby room but a flower pot in the garden"
N-ary relations: Relations with more than two participants

Design Principles

Pattern Reusability

DUL classes and properties are designed to be reused across domains. Rather than creating domain-specific concepts from scratch, ontology designers:

Identify relevant DUL patterns
Specialize DUL classes for their domain
Combine patterns to create rich domain models

Simplicity over Formal Completeness

Unlike DOLCE, DUL favors:

Intuitive naming: "Object" instead of "Endurant", "Event" instead of "Perdurant"
Relaxed constraints: Fewer formal restrictions for easier adoption
OWL2 expressivity: Uses OWL2 features but avoids overly complex axioms

Social and Cognitive Orientation

DUL gives special prominence to:

Social objects: Entities that exist through communication and shared understanding
Information: Abstract information vs. concrete realizations
Descriptions: Conceptual schemas that organize experience
Agency: Agents, roles, tasks, plans, and intentional action