We have two new members on the dem mailing list:
Lars Hansen and Michael Werner.

Mike has an interesting question about inlaws.

>From werner@ccs.neu.edu Wed Jun 11 09:16:07 1997
>From: Michael M Werner <werner@ccs.neu.edu>
>Subject: Re: role of ordering graph
>To: lieber@ccs.neu.edu (Karl Lieberherr)
>Date: Wed, 11 Jun 1997 09:16:05 -0400 (EDT)
>
>I like the idea of a set S of entry nodes as opposed to trying
>to use the "vertex base" of the graph.  As you may know I look
>at these things from a software engineering viewpoint.  The vertex
>base is imho too unstable a set to be useful plus it doesn't
>correspond to any software design construct that I know about.

I agree.

>
>I am wondering if the latest formulation of a "strategy"
>would allow an elegant strategy for the inlaws problem I
>presented last year:
>
>A person object has a reference, spouse to another person object,
>and siblings to a set of Person objects.  An inlaw is either the
>spouse of a sibling or the sibling of a spouse.  The task is
>to find all the inlaws of a given person.

Excellent question.
Here are some possibilities:
Which are the right ones?

Class graph:
Person = [<spouse> Person] [<siblings> NList(Person)].
NList(S) ~ S {S}.

==========================================================
The strategy graph is cyclic and has one node labeled Person.

Person . 
( 
  through -> *,spouse,*   Person . through -> *,siblings,* Person
+
  through -> *,siblings,* Person . through -> *,spouse,*   Person
)

==========================================================
The strategy graph is acyclic and has 4 distict nodes labeled Person.

start#Person . 
( 
  through -> *,spouse,*   sp#Person . through -> *,siblings,* inlaw#Person
+
  through -> *,siblings,* si#Person . through -> *,spouse,*   inlaw#Person
)

==========================================================
The strategy graph is acyclic and has 4 distict nodes labeled Person.
through! means that the edge may be taken only once.

start#Person . 
( 
  through! -> *,spouse,*   sp#Person . through! -> *,siblings,* inlaw#Person
+
  through! -> *,siblings,* si#Person . through! -> *,spouse,*   inlaw#Person
)
==========================================================
The strategy graph is cyclic and has one node labeled Person.
through! means that the edge may be taken only once.

Person . 
( 
  through! -> *,spouse,*   Person . through! -> *,siblings,* Person
+
  through! -> *,siblings,* Person . through! -> *,spouse,*   Person
)
==========================================================


>
>		Mike
>