Maximal Tractable Subclasses of Allen ' s Interval Algebra : Preliminary

This paper continues Nebel and B urckert's investigation of Allen's interval algebra by presenting nine more maximal tractable subclasses of the algebra (provided that P 6 = NP), in addition to their previously reported ORD-Horn subclass. Furthermore, twelve tractable subclasses are identiied, whose maximality is not decided. Four of these can express the notion of sequentiality between intervals, which is not possible in the ORD-Horn algebra. The satissability algorithm , which is common for all the algebras, is shown to be linear.