ActiveFacts (was "ORM is the ...")

At 1:30 PM +0900 4/1/07, Clifford Heath wrote:
The only solution is a system that enables us to completely
hide the physical layer from the user (from the queries),
and that's what fact-based modeling can do. The details of
how are contained in Terry Halpin's book "Information
Modeling and Relational Databases", and are implemented in
at least four significant database design tools, three of
which he designed (the other is CaseTalk, www.casetalk.com).
The most recent is an open source plugin for Visual Studio
called NORMA, which is available as a CTP as the "orm"
project at <http://sourceforge.net/projects/orm/>. Talk
about an iceberg in hell! This thing is already *way* cool.
I'm visiting the team (which Terry leads) for two days in
May before the Rails conference.

I'm a big fan of ORM2 (The current name for the ORM effort).
I'm not a database wonk, but I play around a lot with graph-
based data structures, and ORM2 fits my needs very well. I
would like to mention 2.5 other technologies that I'm hoping
to tie together with ORM2, Ruby, and Rails.

* Conceptual Graphs (Dr. John Sowa, et al)

Although CGs use a different notation than ORM2, both
systems describe hypergraphs (graphs in which edges
may have more than two endpoints: "John took the train
to Chicago"). While ORM2 maps nicely into relational
DBs, CG maps nicely into predicate calculus.

* Ruby Graph Library (RGL; Horst Duchene)
GRAph Theory in Ruby (GRATR; Shawn Garbett)

The basic idea in RGL and GRATR is a mapping between
graph nodes and objects. This lets you, for example,
ask a node about its neighbors, forward messages to
them, etc.

It seems to me (SciFi alert) that it should be possible to:

* extend RGL/GRATR to have both nodes and edges as objects,
such that you can ask an edge about the objects it links

* back the resulting graph by an ORM2-style database (this
would let me ask cross-graph questions such as "which As
have a B relationship with Cs").

* send links (predicates) to a KR system (e.g., PowerLoom)

In fact, I've been musing about how close Active Record is to
being able to support a subset of this scheme. Consequently,
I found your posting _quite_ interesting.


One problem I see with using AR join tables for relationships
is that there seems to be a presumption that there is only a
single reason why a set of tables would be joined. So, "Rich
drives a Camry" and "Rich owns a Camry" live in cars_people.

My working plan is to use a "type" field (ala STI) in each
join table to disambiguate these cases. Not pretty, however.
The discussion in

http://wiki.rubyonrails.org/rails/pages/ManytoManyPolymorphicAssociations

hints at some of the difficulties with this approach.

Another problem is that (apparently) AR doesn't support join
tables with more than two columns. Given that I need hyper-
edges, this loses badly. So, it looks like I need some model
(e.g., acts as) code...


The remaining problem is that the existing tools are only
design tools, that generate database schemata and static
data layers.

There's also the slight problem that NORMA requires Visual
Studio, C#, M$Windows, etc.

What's needed in addition is a flexible runtime
and query processor, written in a dynamic language, and it's
to create such an animal that I registered the ActiveFacts
project on RubyForge. There's no content there yet (sorry
Christian), but if anyone who's willing to do the background
study, they're welcome to help out. I hang out on the new
Yahoo group "information_modeling", and need folk to discuss
ActiveFacts with while I develop it to the point where I have
enough on which to base collaboration.

I'd be happy to be part of the discussion.

-r
--
http://www.cfcl.com/rdm Rich Morin
http://www.cfcl.com/rdm/resume rdm@xxxxxxxx
http://www.cfcl.com/rdm/weblog +1 650-873-7841

Technical editing and writing, programming, and web development

.

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