Need help with a complicated use of composed_of()

I am using composed_of() in a model that maps a
complex data
structure (simply stored in a blob field in the table) to a custom
class. Like this:

class Master
< ActiveRecord::Base

composed_of :marc, :class_name => “Marc”, :mapping => %w(source)

end

class Marc

include
Comparable

end

This works beautifully so far in both directions
(loading up
from the db and saving to the db). I am
now faced with a particularly difficult problem.

In this complex data structure I would like to
store values
that map back to other tables in the database.
For example, one of the elements of the data structure refers to
a
person. I have a standard People model
with all the bells and whistles. When I
unravel the complex data structure (in Marc class) I want to lookup
people from
the people table primarily for data integrity purposes. For this
purpose I can
store the primary ids of people records in the data structure. Furthermore, when the user comes to edit
this data structure (in a ludicrously complicated data entry form) I
want them
to be able to lookup values from the people table in order to select
and insert
into this data structure.

There are several occurrences of people throughout
the data
structure so it would be wasteful to perform separate lookups as
show.rhtml or
edit.rhtml come across them. I have a
way of asking the custom class (Marc) to fetch all these “foreign keys”
from
the data structure before I start building the form and, hence, do one
big
fetch.

My first question is this:
is there a way I can use the usual ActiveRecord mechanism to
manage this
or do I need to manage the satellite tables (People) directly in Marc
class. That is if I had Marc class inherit
from ActiveRecord::??? like standard models (even though Marc is not a
whole table
or standard model unto itself) would this be completely illogical? I ask this because it would be nice to take
advantage of some of the mechanisms in ActiveRecord without actually
being an
ActiveRecord if you get my drift.

I see the current setup as:

Master (db table) -->
Marc (custom, non-db) -->
People (db table)

And lastly - is this the best way of dealing with
this type
of setup? I would like to hear opinions
from people on other possible approaches bearing in mind that the data
structure (handled by Marc class) is incredibly complex and cannot be
stored in
a normalised form in the database.

Apologies for such a long post, and kind regards,

Chad
Thatcher.