RM and abstract syntax trees

#91

Ed Prochak wrote:

Quote:

On Nov 12, 9:42 pm, paul c <toledobythe... (AT) ooyah (DOT) ac> wrote:
[]

Pointers of either kind are nothing more than implementation devices
when it comes to the RM. I'm even getting the impression that some
people think a data design that involves surrogate attributes must
involve pointers.

No I am saying that too many new Relational Database developeres treat
surrogate attributes as if they were pointers.

This seems to imply that those are the only kind of
attributes that could do that whereas I would say that as far as the RM
is concerned, no attributes are ever equivalent to pointers. If one is
using a dbms that has a feature to generate keys, I don't see why one
would take that to be a relational feature, don't see why a logical data
design needs pointers in the first place, don't see what surrogates have
to do with the RM, don't see what lazy instant gratification has to do
with logical data design, blah, blah, blah.

You nailed it, "lazy instant gratification".

Surrogates do come into RM at the higher normalization levels, I
think.
Can one of the knowledgable theorists correct me here?

"Surrogates" have nothing to do with normalization. The design criteria
for keys are: uniqueness, irreducibility, simplicity, stability and
familiarity. Sometimes the criteria conflict requiring design tradeoffs.

A lot of developers ignore familiarity as a criterion. Regardless
whether one adds an extra numeric attribute as an arbitrary key, one
needs to declare all candidate keys to the dbms, or the dbms cannot
manage integrity.

#92

On Nov 13, 9:26 pm, "David Cressey" <cresse... (AT) verizon (DOT) net> wrote:

Quote:

Now maybe we can get back to RM and abstract syntax trees, the main topic
of discussion.

Is there anything about syntax parsing that makes the RM an awkward tool for
modeling it?

Consider that a string is represented relationally (eg as a mapping
between index position and character) and an AST is represented
relationally, I have doubts whether RM/RA itself could offer any
particular advantages (with its set level operations) for the problem
of parsing the string into the AST for some given grammar, even if
teamed up with a functional, imperative or logic programming language,
or direct support for transitive closure. Either a counterexample or
some formal justification for that conjecture would be interesting.

I also doubt whether RM/RA offers any particular advantages for
subsequent processing of a relational representation of an AST. For
example, does it help with unification?

Does anyone have any insights on these questions?

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RM and abstract syntax trees

comp.databases.theory comp.databases.theory

Re: RM and abstract syntax trees - 11-13-2007 , 03:19 PM

Re: RM and abstract syntax trees - 11-13-2007 , 06:33 PM