Introduction

Ontologies are now widely used for representing information regarding a universe of discourse. Many ontology modeling environments have been created, which though provide built-in support only for basic data types, while support for other information structures, although possible to some extent, is not adequately handled. This work is an extension of the Protégé tool to accommodate the modeling and presentation of:
  • entity history, i.e. past values of properties and/relationships; each such value is timestamped with the period that it was (or will be) valid in the real world. To this end, the presented extension provides:
    1. integrated support for data types expressing time quantities – more specifically dates (individual points in time) and periods (anchored segments of the time axis).
    2. data types for storing histories of properties of different types (strings, integers, floats, booleans and instances [i.e. relationships]).
  • weighted data, i.e. data where each value is associated with a real number, its weight. This can serve as a degree of confidence for fuzzy/uncertain data or for any other application-defined purpose.
The extension can be used in contexts that the modeling of entities’ history or representation of weights is important, such as historical archives, museums, fuzzy and uncertain data management etc.