Re: Schema

On Thu, 2002-02-14 at 18:18, Derrell.Lipman_at_UnwiredUniverse.com wrote:
> (I'm trying to get this back onto gpe_at_handhelds.org rather than with
> individual addresses.)
>
> Owen Cliffe <occ_at_cs.bath.ac.uk> writes:
>
> > There is a problem with having the standard/user-defined contact types
> > both in the database in that the typeIDs of the user types will start
> > from where the pre-defined types left off, which will cause a future
> > compatibility should we add more user defined types, so we want a way of
> > all the new user-defined types starting with a typeID > some constant
> > which is about (0x0000ffff) but this means that to add a user-defined
> > type you would:
 
> Maybe you can elaborate a bit, since I'm not quite following why it would
> matter what's pre-defined and what's not. If the list of possible contact
> types were presented to the user ("SELECT contact_type_name FROM
> contact_types;" -- no WHERE clause)
> he'll see all of them. If new types,
> whether "pre-defined" or otherwise, are added later, they would get the next
> available ids. I missing what you're trying to get at, as I don't see why
> this is a problem.

For external interfaces mainly, and for base-line support in apps etc.
say for example a contact manager had a GUI form which only edited the
Basic types it is important that they have a way of referring to those
types when they get round to adding stuff to the database, its just
easier from an app-programmers point of view to have an alias for say
address, the separation thing is just to ensure that the 2 classes of
contact type can be grouped into two sets of contiguous IDs)

likewise a lot of external interfaces (say synchronization, or for
example a VCard transmitter) have to deal with the basic types in a
different way to any user-defined types, and the user-defined types may
become meaning less.

its easier to "SELECT contact_value from contacts where type=ADDRESS"
(where address is a defined constant) than always having to do

SELECT contact_value from contacts,contact_types where contacts.type_id
= contact_types.id and contact_types ="address".

Its just a way of saying: You can safely use these types and here is an
easy way of reffering to them.

owen

-- 
Owen Cliffe, Ph.D. Student, Dept. Computer Science
University of Bath