Re: About MS-Access RDBMS
- From: "Srinivas" <Srinivas@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Mon, 11 Apr 2005 18:33:02 -0700
Thank you very much Tim, this what I expected.
I'm a developer on VB looking to build prototype applications on MS-Access.
Working in Malaysia, Could you tell me how about the VBA and Access market
now.? would you advise me switch to these techies from VB.
Thanks
-Srinivas
"Tim Ferguson" wrote:
> "=?Utf-8?B?U3Jpbml2YXNhbg==?=" <Srinivasan@xxxxxxxxxxxxxxxxxxxxxxxxx>
> wrote in news:86190119-FA54-4665-AD9C-BFC659ABE540@xxxxxxxxxxxxx:
>
> > Can we say MS-Access as True RDBMS?,
>
>
> I have a feeling that this is a troll, but in any case I'm sucker enough
> to bite... Codd describe the twelve rules of relational fidelity, and
> Pascal added rule 0.
>
> 0) Foundation rule: a relational dbms must manage databases entirely
> through relational capabilities.
>
> The mdb file is a monolith, and it's not possible to pretend that tables
> in different file can be related, and there are no tools to manipulate
> the data in mdb files directly; so this is a pass.
>
> 1) Information rule: all information must be held in R-tables.
>
> Access allows tables to be created without primary keys and therefore
> fails rule 1.
>
> 2) Guaranteed logical access rule: every value must be accessible via
> table name, PK value and column name.
>
> Since Access fails rule 1, this also fails by definition.
>
> 7) Set level operation rule: select, insert, update and delete operations
> must be available via set operations rather than requiring row-by-row
> manipulation
>
> Within the limitations of the language, all these operations are called
> by SQL and so this is a pass.
>
> 3) Missing information rule: missing information should be handled by the
> database not by applications' own exception processing features.
>
> Access provides NULL handling on all data types except booleans. Note
> that Codd himself had big problems with proper handling of null data, so
> Access is not significantly worse than any other product. I think MVDBMSs
> are meant to be better, but I don't understand enough to make a valid
> judgement.
>
> 8) Physical independence rule: applications and interactive operations
> should remain independent of internal storage mechanisms.
>
> Microsoft only provides access to (logical) data via the Jet engine, and
> the internal (physical) structure of mdb files is a deep mystery which
> may or may not change from one version to another. This rule is therefore
> a pass.
>
> 9) Logical independence rule: applications and interactive operations
> should remain independent of the structure of the base tables.
>
> Access does not support views as an alternative to direct base table
> access -- queries are partly updateable and cannot always be substituted
> for base tables. This is at best a partial pass, and strictly it's a
> fail.
>
> 6) View update rule: the rdbms should identify at definition time whether
> or to what extent a view can be updateable.
>
> I have a feeling that Access should do this, but updateability seems so
> unreliable and paradoxical that I can't use the capability. In my hands,
> Access fails this rule, but it may be that in others' more experienced,
> it's at least a partial pass.
>
> 10) Integrity independence rule: operations and applications should be
> independent of internal integrity declarations.
>
> Access can define unique key and foreign key integrity rules, validation
> rules that cover one table and rules across multiple tables.
> Unfortunately, the user interface makes these hard and often pretends
> that they are optional, so although this rule is a pass, Microsoft loses
> credit for trying to obfuscate it.
>
> 11) Distribution independence rule: operations and applications should be
> independent of distribution and re-distribution of the database
>
> I don't have a lot of experience with Jet replication, but I gather that
> the applications run just as happily against a replica as with a real
> database, so this is a pass. Just whether replication counts as true
> distribution is another argument and it's well over my head!
>
> 4) Dynamic online relational catalog rule: The database description
> should be held just like ordinary data i.e in R-tables
>
> Access nearly gets a pass on this. Actually, the entire schema is held in
> R-tables, but then agan Microsoft has officially not documented these and
> the only reliable access is via proprietary dao or adox libraries. In
> practical terms, therefore, it's a fail.
>
> 5) Comprehensive data language rule: there should be one language to
> support all the relational features of the database - data definition,
> data manipulation, integrity rules, authorisation etc.
>
> Access has a pretty complete implementation of SQL DDL and DML; but it
> does not use the same langauge for security features or the system
> catalog or queries, so this is a fail.
>
> 12) Non subversion rule: operations in a native language should not be
> able to subvert data integrity rules declared in a higher-level language.
>
> Access does not allow the DAO library (for example) to break integrity
> rules, so this is a pass.
>
> Summary: Access passes seven out of thirteen rules for relational
> fidelity. It's up to you whether this makes it a True RDBMS, or even
> whether you think that a product can be half-relational. Are you looking
> for a platform to learn about relational theory and design? Are you
> looking for a standardised environment to develop a mission-critical
> database? Are you comparing with other desktop products, or with
> industry-strength software systems costing thousands of dollars?
>
> All the best
>
>
> Tim F
>
>
.
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