Newbie just getting started with V4RB: Is-a relationships

[Stefano Franchi]

Hi all,

	I am just getting started with Valentina for RealBasic, and I need to 
clarify a couple of issues about hierarchical relationships in 
Valentina before I get started with database design.

	Say I have an object "Book"  with all the usual fields. It is a 
subclass of VBaseObject. If I need to specialize Book into 
"ManuscriptBook" (for example) can I subclass it and inherit all the 
properties of Book? This is what some Object-relational RDMS  like 
PostgreSQL allow.   But I'm not clear if Valentina allows it as well.

If it isn't possible, how do people normally implement Is-a 
relationships like this one in Valentina? Two standard approaches come 
to mind:

a.  With manually maintained 1-1 relationships between child and parent 
tables? Or


b. with so-called "horizontal" design (i.e. by having only children and 
replicating all the parent's fields in each table)?

I very much prefer the first approach, but it usually takes quite a 
significant performance hit in traditional RDBMS, because of all the 
joins needed to reconstruct the complete entity. Design is cleaner, 
though, and easier to maintain. Is Valentina's famed speed a good 
reason to dismiss the performance hit? Does it even suffer from it (I 
have no idea, yet I hope, of how different Valentina is from a RDBMS 
internally)?


Thanks for the help,

Stefano

_____________________________________________________________
Stefano Franchi
Department of Philosophy        Ph:  (64) 9 373-7599 x3940
University Of Auckland			Fax: (64) 9 373-7408
Private Bag 92019				s.franchi at auckland.ac.nz
Auckland
New Zealand