Re: Just one more anecdote

On 4 Aug 2005 14:13:38 -0700, Marshall Spight wrote:

>Hugo Kornelis wrote:
>> An ORM diagram maps to
>> tables, primary key, unique, check and foreign key constraints,
>
>... which tables handle just fine...
>
>> plus a
>> bunch of constraints that can't be directly implemented in any RDBMS
>> that I know of.
>
>Like what? What can't a CHECK constraint do?

Hi Marshall,

See the examples in my post to Kenneth.

>> I'd say that stating the needs as table definitions is incomplete.
>
>Can any of the other software in the system take advantage of
>these constraints? If so, why can't the dbms do so also? If not,
>what value are they?

Not automated, if that's what you mean. That would require tools that support ORM in a way that goes far beyond what's currently available in Visio.NET.

But a front-end coder could easily look at the model, see an exclusion constraint and decide that input field 2 should be disabled if there is anything in input field 1, and vice versa. Or (in case of an equality constraint) move the cursor to field 2 when something is entered in field 1 and require the user to input something before allowing him to move on to other fields.

I guess that automated front end builders could do the same. But AFAIK, nobody has yet created an automated ORM-based front end builder.

Best, Hugo

-- 

(Remove _NO_ and _SPAM_ to get my e-mail address)