IMPORTANT NOTE: I've rewritten the code below in Python and expanded on its capabilities. See https://github.com/alreich/qualreas

Algebras for qualitative reasoning about time, space, etc.

NOTES:

• This code was written in the early 1990s and has only been partially tested since then using Armed Bear Common Lisp (ABCL). The portions tested appeared to work OK. However, it does not appear to work using Steel Bank Common Lisp (SBCL).
• As of November 2020, an updated version of this code is in-development and nearing completion using Python

The code here was used to write the following paper (a copy is in the "docs" folder of this repository):

"Intervals, Points, and Branching Time", Alfred J. Reich, Time-94: An International Workshop on Temporal Representation and Reasoning, 1994.

ABSTRACT: This paper extends Allen’s interval algebra to include points and either left or right-branching time. The branching time algebras each contain 24 relations: Allen’s original 13 relations, 5 more relations resulting from the inclusion of points, and 6 relations because of the inclusion of branching time. In this paper, I also present:(1) A technique for automatically deriving algebras of relations;(2) a new way of representing temporal constraint networks—the constraint matrix; and (3) a new way of performing constraint propagation—via constraint matrix multiplication.

An OWL (Web Ontology Language) ontology is also included, in TTL format. The ontology extends the World Wide Web Consortium (W3C) ontology, https://www.w3.org/2006/time, to include Time Points (Instants) and Intervals, where the relations are as defined in the Time-94 paper referenced, above. A description of W3C time can be found here: https://www.w3.org/TR/owl-time/