Re: [binarycloud-dev] entity definition format

[John D. <jo...@we...>]

On Fri, 17 Aug 2001, Alex Black wrote:

> >> I can see use in having separate "settings" for the database and the app.
> > Jepp. I think this is neccessary.
> > 
> > Another question. Can a entity span say parts of one or more tables?
> > Something similar like a view in SQL?
> 
> "Sort of"
> 
> you can embed entity references (called pointers) in entity definitions.
> 
> so you can say:
> 
> user_id
> user_name
> user_password
> address_id -> address
> 
> i.e. "get the address entity with this id"
> 

Yep.

> > In the example the complete db entitys are mapped in the definition. And so
> > querys are genearated for all fields. But that might me overhead. So I would
> > like to define a entity that spans parts of tables.
> > 
> > E.g. If I have a enty defined called "Subscriptions" that span the
> > tables.fields:
> > 
> > user.userId
> > user.login
> > smssubscriptions.userId
> > smssubscritpions.serviceId
> > emailsubscriptions.userId
> > emailsubscriptions.serviceId
> > 
> > but the tbl user has more fields I do not need to query for this entity. But
> > for this one it's just fine.
> 
> I don't see why not. I don't _think_ entityManager supprts that currently
> but I have no problem with the idea as long as its implemented properly :)
> 

It does support that; you have to specify the joins in a hierarchical array
structure in the entity definition (that syntax could use some rethinking
before we release as it was imported from an earlier abstraction layer). I can
supply an example entity definition if there is interest.

> ------------
> 
> Actually, along these lines: does anyone have any qualms about making this
> assumption?:
> 
>     -Entity Field names must correspond exactly to table field names (we
> could get rid of the schema map if we did this)
> 

The schema structure is optional; if it's not present, we use the object
structure, which is single-dimensional, instead. Odysseas or John C.  will
probably have better rationale for this than I do, but at least one example of
where the schema mapping comes in useful is in building a generic public data
access structure which could be used to automatically generate, for example,
dtd's for XML access to these objects. Having a degree of independance between
your data access structure's element names and your database field names could
prove useful for cases like this.

HTH

-- 

John Donagher
Application Engineer, Intacct Corp.

Public key available off http://www.keyserver.net
Key fingerprint = 4024 DF50 56EE 19A3 258A  D628 22DE AD56 EEBE 8DDD