Re: Lucid statement of the MV vs RM position?

dawn wrote:
> Jon Heggland wrote:

>> Other writers claim they *do* know of such applications, however, and
>> have proposed (semi-)formal guidelines for identifying cases where RVAs
>> may be appropriate.

"Simple" meaning "not relation-valued"?

> For example, we model data for XML
> documents for data exchange using multivalues even if we could do
> otherwise.

You do? Why?

I don't see the relationship between XML, RVAs and normalisation. Normalisation by definition applies to relations/relvars only. (I must confess I haven't seen the light with regard to using XML for exchange of data to/from relational systems either.)

> Are there best practices for that?

You tell me. Isn't "modelling" "data for exchange" just producing reports? In which case you do what is most convenient for the task at hand. Which is very different from designing the database, where you (or at least I) want it (i.e. the logical model) to be as orthogonal, unbiased and simple as possible.

> Would any of those best
> practices be applicable to modeling persisted data as well? If data
> for exchange is persisted (perhaps in a database such as IBM Viper when
> that comes out), it would make sense that the best practices for
> modeling data for exchange and persistence would overlap, right?

I don't know, but I'm skeptical. Why do you want to "persist" "data for exchange"? (I'm not really comfortable with either of those terms.)

-- 
Jon