Declarative Priority In A Concurrent Logic Language ON
Keiji Hirata, Yamazaki Kenichi
Abstract:
It is well known that priority control is essential for real-world
problems, and actually, many real-world-oriented concurrent
logic/constraint languages, such as KL1 and Oz, can deal with priority
in explicit or implicit ways. However, the design policies of these
languages in terms of priority were ad hoc, since priority has been
considered non-logical. It turns out that its procedural meaning has
been given in an informal way at most. Our aim is to construct a
formal declarative semantics of a prioritized program in order to
increase applicability of concurrent logic languages to real-world
problems. In this paper, we first define a model of priority and
prove some properties of the model. Then, we design a concurrent
logic language ON based on our theoretical framework and discuss some
prominent characteristics that are embodied in sample programs written
in ON. The results presented in the paper provide a new insight into
priority from the declarative point of view.