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:zz,skx: Preflet piece explanation / Slices

I haven't had a chance to look at Andrew's
 archive site, so I've just sent the piece along again.

By a single mechanism I sought to embrace the following
 desiderata, and I think succeeded.

1) allow unbreakable links (part of the '86ish specifications)
2) allow order-unchangeable links (where elements could
 be inserted)
3) allow the sliding in of additional cells from collections
 of cells called "slices" (files of cells segregated by the user
 and swapped out), whose cells could actually be insinuated
 in existing ranks.

The preflet mechanism expresses all of these in a compact way.
 I believe it is combinatorially well-behaved and places little
 burden on structural operations.


At 10:31 AM 10/28/98 -0500, you wrote:
>> This "conjoinment" may be a good term.  I have
>>  been noticing that you generally want new dimensions
>>  in pairs in just this way,
>> d.inside / d.contents
>> d.mark / d.marklist (tells what cells are part of
>>  "the same mark")
>That's what I was thinking.  Any time someone is going to want to have
>a relationship that is one-to-many, they will need to do this.
>> "Transitive" means that ordering is important. 
>Not exactly.  Order can be important wihout being transitive.
>	---> d.ancestor
>	A--B--C
>Here you want --- links to express `ancestry'.
>A is the ancestor of B, and B is the ancestor of C.
>But it is transitive, so A is also the ancestor of C.
>	---> d.child
>	A--B--C
>Here you want --- links to express a parent-child relation.
>A is the parent of B, and B is the parent of C.
>But is is *not* transitive, so A is *not* the parent of C.
>The two pictures look exactly the same, so if ZZ is going to
>understand the difference between these two pictures, there will have
>to be an explanation somewhere else.
>> See my paper on Preflets
>> I think 1 and 3 come from somewhere else
>>  (as you see, I'm no mathematician) and may not 
>>  have meaning or relevance.  Hey, I'm open--
>I wrote them down because I ran into examples where they were
>Symmetric means that in A---B, A is related to B in the same way that
>B is related to A.  If you hop A over B and make it B---A, the meaning
>does not change.  Example: d.contents is symmetric.  d.inside is not.
>If ZZ is going to do things like selecting and gathering cells
>automatically, it will have to understand something about the meaning
>of the structures you build.  Symmetry and transitivity are both
>important here.
>In an earlier message, I suggested that there could be an operation
>for automatically alphabetizing cells:
>	---> d.sex
>	MALE   -- Homer -- Bart -- Ned -- Barney -- Moe -- Snake
>You'd put the cursor on MALE, press the button, and the structure
>would become
>	MALE   -- Barney -- Bart -- Homer -- Moe -- Ned -- Snake
>In order to do this, ZZ must know that d.sex is symmetric and
>transitive.  Otherwise it should give you a warning first, because
>what you are asking for makes no sense, and if you try to alphabetize
>in a dimesion that is not symmetric or transitive, you will change the
>meaning of the structure:
>	---> d.son
>	Grandpa -- Dad -- Ted
>	||   Alphabetize
>	\/
>	Dad -- Grandpa -- Ted        (ooops)
>> >There were a couple of others I thought of, but my notebook is
>> >downstairs.
>> Uh-oh.  You DEFINITELY are one of us.
>My notebook is now in the compuiter, so beware.

Theodor Holm Nelson, Visiting Professor of Environmental Information
 Keio University, Shonan Fujisawa Campus, Fujisawa, Japan
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