Re: [Gnue-dev] New Architecture Drawing based on Whitepaper.

[Stanley A. Klein]

At 06:39 AM 12/5/2002 -0500, Reinhard Mueller wrote:

>Am Mit, 2002-12-04 um 21.16 schrieb Stanley A. Klein:
>
>> What I mean by "traceability of the data" is that it is possible, given t=
>he
>> way a data item is defined on one side of appserver, to identify the data
>> item on the other side of appserver.
>
>Thanks, now I got it. Thanks for your very good explaination.
>
>I can assure you that this will be the case. It's an important point not
>only for security, but also for maintainability of the underlying
>database.
>
>The way how table and field names ("backside of appserver") are created
>from class and property names ("frontside of appserver") will be well
>documented, straightforward and easy to understand.


Reinhard -

I'm glad to see that you intend to have the front side to back side
mappings easy to understand.

However, there is a challenge in trying to do this that is evident from
your terminology.  "Table and field names" implies a relational paradigm.
"Class and property names" implies an object paradigm.  

If the front side is relational and the back side is relational, there is
no problem.  Likewise, if the front side is object and the back side is
object, there is no problem.  In both cases the mapping should just flow
through from one side to the other.

I'm not sure if there is a problem when the front side is relational and
the back side is object.  I think it is easy to map a relationsl structure
into an object structure.

However, if the front side is object and the back side is relational, I
think there may be a problem.  These kinds of mappings tend to be complex
and less easy to understand.  Objects can have structures that don't easily
map into tables and fields.

There is also the continuing issue of commonality with Common and the
two-tier model.  As I understand it, Common allows a front side relational
paradigm for the two tier model.  

These considerations were what I was asking about in my question about "the
schema
being expressable in either SQL/gsd or gcd."  SQL is in the relational
paradigm and gsd looks like it is.  However, I think gcd is in the object
paradigm.  I would be interested in learning how you plan to address this.  


Stan