About MS-Access RDBMS

I think your description misses the point out of rule 1:

Rule two says that tables have primary keys.

Rule one says that not just 'data', but foreign key
index definitions, stored procedures, permissions,
constraints, etc etc are stored in tables.

When properly formulated, the rules should be orthogonal:
ie you shouldn't be able to say 'fails rule 2 because it
fails rule 1'

(david)


"Tim Ferguson" wrote in message
...
"=?Utf-8?B?U3Jpbml2YXNhbg==?="
wrote in :

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