G-Man:
You say:
"A fundamental difference between MV and relational
is as follows:
- In a relational DBMS, a DBA defines RI at the database level.
The DBMS enforces the rules.
- In MV, a programmer defines RI at the application level. BASIC
code enforces the rules. This is why MV shops generally don't
have DBA's, they just have programmers."
I think that's what Wol meant with his comment. There is referential
integrity but it's done differently and in the hands of different
people. To say MV doesn't have referential integrity because it
doesn't do it at the database level is like saying the RDBMS doesn't
have referential integrity because it doesn't do it at the application
level.
Do you remember the D3 file function (bridge processing) that maintained
referential integrity? When we updated one file it took the value of an
attribute and updated the other file with that key. I have no idea why
that idea didn't go past D3.
Don't get me wrong, I know the limitations of the MV model, as I do the
limitations of the RDBMS model; so I'm not debating this here. I'm only
mentioning that Wol has a point, and that D3 did have some interesting
referential integrity capability that the other MV models don't. :-)
Bill
------------------------------------------------------------------------
Tony Gravagno said the following on 9/19/2009 2:54 PM:
From: Anthony W. Youngman
Please - define "referential integrity". In a MV
database, for the most part, orphan records don't
happen because MV *does* enforce integrity. It just
does it completely differently - it stores related
attributes together so they can't get orphaned, rather
than scattering them across multiple tables. As has
been pointed out before, it's easy to make a mistake
when defining your relational database. Those sort of
mistakes just don't tend to happen with an MV database.
Sure they do. A fundamental difference between MV and relational
is as follows:
- In a relational DBMS, a DBA defines RI at the database level.
The DBMS enforces the rules.
- In MV, a programmer defines RI at the application level. BASIC
code enforces the rules. This is why MV shops generally don't
have DBA's, they just have programmers.
[snipped]
Tony Gravagno
Nebula Research and Development
TG@ remove.pleaseNebula-RnD.com
remove.pleaseNebula-RnD.com/blog
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