[elephant-devel] Mirroring classes from 3rd party packages.

[Yarek Kowalik]

I have a dilemma deciding on the structure on persiting data.  I need your
advice on.

I'm relying on a third party package (Amazon-ECS) that helps me parse Amazon
XML data feed, with the result that the XML is translated into a set of
nested CLOS objects (all classes use metaclass ELEMENT-CLASS).   The XML
documents are represented by a root object, and there subparts of the XML by
the nested objects accessible via root object slots, and so on
recursively.   It's actually a small tree structure of various types of
objecs at each level.   The data within this structure is valuable for
current and future needs for the project and I would like to cache it
instead of fetching from Amazon (there is a limit on how much you can fetch
at one time, plus the volume would make it prohitive).

For the purpose of the application, currently I only need a small subset of
the data.   As a solution I thought that perhaps can I just create a facade
object that will contain the basic data slots I need plus an
OBJECT-REFERENCE field that refers to XMLRoot (and the objects hidden
within)? When this facade object is persisted, will the entire XMLRoot with
its descendends (objects refering to objects either through slots or lists
in slots) be persisted?  That is, when an object is serialized, is the
serialization recursive?

The second option is to build a set of persistend mirror objects for the XML
objects I get and copy the data onto it.  This probably can be automated
somehow.

The third option is to modify the package Amazon ECS parsing package to use
persistent objects by default.  It's problematic, because now I will
effectively create a branch of the package and maintain it separately from
the core.  I would not want to persist all of the classes, so I would have
to be selective - it isn't simply making Amazon-ECS' ELEMENT-CLASS an
Elephant's PERSISTENT-CLASS.

Any clarifications and advice would be much appreciated.

Thanks,

Yarek
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