  This paper combines two important directions of research in temporal
resoning: that of finding maximal tractable subclasses of Allen's interval
algebra, and that of reasoning with metric temporal information. Eight new
maximal tractable subclasses of Allen's interval algebra are presented, some of
them subsuming previously reported tractable algebras. The algebras allow for
metric temporal constraints on interval starting or ending points, using the
recent framework of Horn DLRs. Two of the algebras can express the notion of
sequentiality between intervals, being the first such algebras admitting both
qualitative and metric time.
