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Topology / ALM-Compiler

A Java implementation of the ALM language that compiles to the SPARC variant of Answer Set Programming (ASP).
Apache License 2.0
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Design issue in ALM - define constant/instance for non-source sort #6

Open zhangyuanlin opened 6 years ago

zhangyuanlin commented 6 years ago

  1. currently constants and instances are only allowed for source sorts.

  2. An alternative is to allow constants and instances for non-source sorts. These constants/instances are taken as not in any of its descendent sorts.

Current Monkey banana program from ALM paper uses non-source sorts in defining constants and instances. They bugs by 1, but they are ok by 2.

Topology commented 6 years ago

I've always felt that the restriction was arbitrary and interferes with reuse.

Scenario: sort A is populated by "normal" instances. sort B extends sort A with some additional state that documents "abnormal" instances of A. I should not have to create a subsort of A that holds the instances that are not in B.

zhangyuanlin commented 6 years ago

May we can summarize the assumption behind the decisions as

  1. parent sort = union of all its child sorts
  2. parent sort is a superset of the union of all its child sorts.
Topology commented 6 years ago

I think it also draws forward the philosophical debate over using sets vs. categories as a foundation of mathematics. I have a tendency to see sorts more as kinds and categories than sets.