Mar 04, 2014: Arend Rensink: If-Next-Also-Else - An Algebra for Rule Scheduling

March 04, 2014If-Next-Also-Else - An Algebra for Rule Scheduling
Room: HalB 2FArend Rensink

To capture the essence of rule scheduling, I propose an extension to the usual
state-transition model. Rather than having a transition reflect only what
should occur after a rule has successfully concluded (from its target state),
in the extended model a transition is explicitly viewed as an attempt, and also
gives information about what should happen when the attempt fails, and when it

This idea allows rules to be scheduled deterministically, and at the
same time accounts for both symmetric and asymmetric (preferential,
try/else) choice. Algebraically, it is captured very fittingly by a single

C ? N & A : E   (read: if C next N also A else E)

expressing that C should be attempted, followed (after it is finished) by N; if
C succeeds, then A is attempted as an alternative, otherwise E is attempted as
an alternative.

I will discuss the motivation as well as and theoretical and practical
consequences of this concept.