Rails - Sep 2005 - Dynamic Relationships

Looking at the ORM write-up in Locomotive, I don''t see how to handle
new relationships on a dynamic basis.  In this application, I''m likely
to be encountering unexpected relationships on a continuing basis.  I
I don''t want to be updating my table definitions on the fly, so I need
a way to add new relationships in a "semi-structured" manner.

One possible implementation would use an "edge list", as seen in:

   *  RDF (http://en.wikipedia.org/wiki/Resource_Description_Framework)

   *  RGL (Ruby Graph Language; http://rubyforge.org/projects/rgl/)

That is, along with the static relationships encoded by foreign keys,
I could encode arbitrary (including dynamic) relationships in an
"edges"
table, as:

<scifi>

   create table edges (
     src_table  varchar(100),
     src_id     int            not null,

     dst_table  varchar(100),
     dst_id     int            not null,

     e_type_id  int            not null,

     id         int            not null auto_increment,
     primary key (id)
   );

</scifi>

In one possible use, you could ask an object for a list of its edges.
Along with reporting on the ones it implements via foreign keys, it
could tell you about ones that are encoded in the "edges" table.  You
could then iterate over the reported edges, seeing what you have.

Before I wander off in this direction, however, I''d like to ask for
feedback.  Is there some better way to handle this sort of problem?
Are there caveats (aside from performance, which is not likely to be
a gating issue in this application)?

Inquiring minds need to know...

-r
-- 
email: rdm-go8te9J4rpw@public.gmane.org; phone: +1 650-873-7841
http://www.cfcl.com        - Canta Forda Computer Laboratory
http://www.cfcl.com/Meta   - The FreeBSD Browser, Meta Project, etc.

you should be keeping your database just as your trying to keep your
database -- non-modified.

database scheme''s should remain stable during any runtime.
adding/deleting tables during production is asking for trouble to
occure in many ways.  as well im not aware of any database that allows
multi-table column referencing.  its entirely to complicated and
unneeded.


On 9/16/05, Rich Morin <rdm-go8te9J4rpw@public.gmane.org>
wrote:
> Looking at the ORM write-up in Locomotive, I don''t see how to
handle
> new relationships on a dynamic basis.  In this application, I''m
likely
> to be encountering unexpected relationships on a continuing basis.  I
> I don''t want to be updating my table definitions on the fly, so I
need
> a way to add new relationships in a "semi-structured" manner.
> 
> One possible implementation would use an "edge list", as seen in:
> 
>    *  RDF (http://en.wikipedia.org/wiki/Resource_Description_Framework)
> 
>    *  RGL (Ruby Graph Language; http://rubyforge.org/projects/rgl/)
> 
> That is, along with the static relationships encoded by foreign keys,
> I could encode arbitrary (including dynamic) relationships in an
"edges"
> table, as:
> 
> <scifi>
> 
>    create table edges (
>      src_table  varchar(100),
>      src_id     int            not null,
> 
>      dst_table  varchar(100),
>      dst_id     int            not null,
> 
>      e_type_id  int            not null,
> 
>      id         int            not null auto_increment,
>      primary key (id)
>    );
> 
> </scifi>
> 
> In one possible use, you could ask an object for a list of its edges.
> Along with reporting on the ones it implements via foreign keys, it
> could tell you about ones that are encoded in the "edges" table. 
You
> could then iterate over the reported edges, seeing what you have.
> 
> Before I wander off in this direction, however, I''d like to ask
for
> feedback.  Is there some better way to handle this sort of problem?
> Are there caveats (aside from performance, which is not likely to be
> a gating issue in this application)?
> 
> Inquiring minds need to know...
> 
> -r
> --
> email: rdm-go8te9J4rpw@public.gmane.org; phone: +1 650-873-7841
> http://www.cfcl.com        - Canta Forda Computer Laboratory
> http://www.cfcl.com/Meta   - The FreeBSD Browser, Meta Project, etc.
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
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> 

-- 
Zachery Hostens <zacheryph-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>