Dear Cameron,
This is why I have taken lately to reminding people that VistA is not
written in MUMPS. VistA (well, DHCP anyway) is written in Standard
MUMPS. The difference, as you know, is the heart of VistA's
portability, and therefore sustainability.
Yours truly,
Rick
Cameron Schlehuber wrote:
The 3-tier architecture with SQL at the database tier permits (in theory)
the ability to swap vendors of the DBMS. The cost is one of performance
unless stored procedures are used ... which then end up tying you to the
DBMS vendor. ANSI M provides a way out of that problem since the business
logic (usually the middle tier) can be combined with the database and the
combination can be ported from one vendor's implementation to another with
the exact same code and not have to change any "stored procedures" as they
are part of the ANSI M code. (Though vendors can certainly have a
significant impact on performance).
Greg wrote:
I find it useful to think in terms of data types. I believe that what
you are saying here is that it is important to abstract away from the
primitives used to implement other types. Just as pointers are the
basic primitive used in a language like Pascal to implement abstract
data types, tuples and relations are the basic primitives used in the
relational world to model other structures. I believe it is
unnecessarily narrow (and in fact, a caricature of the relational
model) to think of the table as the basic *abstraction* of this model.
That would be like saying pointers and subfiles are the basic
abstractions with which one works in Fileman. That's just not true.
They are *primitives* used to model abstractions that can be quite
complex.
Think about this way: Bricks and mortar may be used to construct
buildings (well, maybe not out here in earthquaqke country), but when
an architect looks at a building, (s)he does not see (just) brick and
mortar. There is much more that can be said about buildings than simply
that they are built out of certain fundamental components.
[...]
===
Gregory Woodhouse
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