Re: Multi-Parent Nodes in org-mode

[Lennart Borgman <lennart.borgman@gmail.com>]

On Thu, Jul 16, 2009 at 11:44 PM, Bastien<bastienguerry@googlemail.com> wrote:
> aartist <aartist@gmail.com> writes:
>
>> I like to have the nodes in org-mode that can have multiple parents.
>>
>> A : 1,2
>> B : 1,3
>> C:  2,3,4
>>
>> The above should easily be transferred too.
>>
>> 1 ! A,B
>> 2 ! A,C
>> 3 ! B,C
>> 4 ! C
>
> I don't see how to do it with a tree structure, and Org-mode is very
> tree-oriented.
>
> Maybe we can emulate this by having just a flat list of tasks and by
> adding two properties :Parents: and :Children:, each one indexing the
> parents' ids and the children ids.  But I don't see clearly how useful
> it would be.

I think the suggestion does not fit tree structures, but a two way
graph like that can be printed in two dimensional space -- ie if you
just print children and parents belonging to one node at a time. You
can look at it as a two-way tree (don't know if anyone actually uses
that term, but it is a subset of graphs).

In case of org-mode and the capabilities you have to show a graph as
text you could simply just show the parents as links, something like
this:

  * Other parent
  ** Other parent child
  * Parent
  ** Child
              # Other parent (make this a link)
                  Other parent body
              ## Other parent child
              # Next parent child (make this a link)
     Child body
  * Next parent
  ** Next parent child

I am not sure this will be tremendous useful in a case like this
however. However I am not sure. It is a common problems when
structuring knowledge so it might be. So if someone wants to use
org-mode for that it may be useful.

For a solution like the one above you have to think about how to
manage editing of the "# parent" part. I think it may be implemented
as 'after-string overlay properties in the buffer, perhaps with some
hooks for updating.