Object Models vs Ontologies Similarities Modeling a particular

Object Models vs Ontologies Similarities: • Modeling a particular subject area • Language Expressivity: similar fundamentals – Classes, properties and instances (individuals). – Sub-Class hierarchy with inheritance • Commercial tools available

Object Models vs. OWL Classes and Individuals/Instances OO: • classes are types, • every instance has unique type, • instances always in same class • set of classes fixed at compile time OWL: • classes are sets of individuals, • individual can be in multiple classes, • individuals can change class at runtime • can add new classes and edit classes at runtime

Object Models vs. OWL Properties, Attributes and Values OO: • Properties attached to single class; inherited to its subclasses. • Classes are primitive, not defined using properties. OWL: • Properties stand alone. Attached to multiple classes via domain constraints and inheritance • Properties are used to define classes.

OWL Classes: Sets of Instances with Common Characteristics Diagram from: A Semantic Web Primer for Object-oriented Software Developers Software Engineering Task Force, W 3 C SWBPD WG

Object Models vs. OWL Properties, Attributes and Values OO: • Instances can have values only for attached properties. Values must be correctly typed. • Data types used for type checking OWL: • Individuals can have arbitrary values for any property • Range constraints used for type inference and type checking

Object Models vs. OWL Inheritance: OO: • Template for creating instances, for programming convenience, not for inferencing • not logic-based, defaults w/ override OWL: • Is strictly logic-based, no overridable defaults. Inference is key. Compuatation / Inference OO: • Closed world: unknown = false. OWL: • Open world: unknown = unknown

Object Models vs. OWL Error and Consistency Checking OO: • Compiler problems indicate errors at build time only OWL: • Reasoners check consistency at build time & run time Maturity OO: • Very mature, vast range of commercial products OWL: • Maturing, commercial vendors recently emerged.