Chris,

>>   Rational model is graph, but xml model is tree -
>> so xml model is sub-set of rational model (i.e. you are wrong).
>>   Of course, you can point artificial exit from this situation:
>> to use PrimaryKey-ForeignKey mechanism in xml attributes.
>>   So two model are identical in this ?
CB> The "primary-key/foreign-key" mechanism you refer to is
CB> part of the XML specification:

Of course, artificial mechanism can be standardized too.

CB> and no more artificial than the equivalent mechanism in relational
CB> databases.

Any technology has own _cental_ idea.
In other technology copies central idea,
it stops be itself, it become imitation.

CB> There are also many constructs in XML that have no correlate whatsoever
CB> in the relational model:
CB> - comments
CB> - processing instructions

Exist

CB> - external entities

what ?

CB> - internal and external references

My proposal
http://sql50.euro.ru/sql5.11.1.ppt , slides 58,76.

CB> - distinction between text in element content and attribute values
+
CB> - mixed content
+
CB> XQuery can address all the facets of XML documents I
CB> described above, which cannot be addressed by "SQL1-4" or "SQL5"

Append field with name '@' into DBMS.
It's possible to refer by '@@' to it,
and by '@fieldname' to all other fields.

Aimless existance (of distinction) is not benefit itself.

CB> - distinction between child elements and references to other elements

The same (read above).

>> There exist much libraries of SQL (SQL 1-4) code ;
>> there exist much applications, writing under SQL;
>> but XQuery is relatively new.
>> So preference should be given to SQL _syntax_.
CB> XQuery is not that new, having been around for several years

But not several tens years (as SQL).

CB> "SQL5" is distinctly new

It's new strongly in so measure, in which it accepts XPath
(to process whole trees instead of tuples).

CB> XQuery implemented by numerous vendors
+
CB> "SQL5" is not in general use or even endorsed by users of
CB> the "SQL1-4" libraries and applications.

XQuery has bulky syntax with repeated cycles.
Its syntax is objectively worse, than syntax of SQL
(XQuery is like Clipper or FoxBase).
And it's not cancealed by fact, that SQL5 is not implemented yet.

---

CB> Your solution is to replace the human pilot with an android robot, because
CB> look! we have already gone to all the trouble to design seats and
CB> parachutes

You think, this solution is not reasonable ??

CB> we don't have any need for seats and parachutes and heads-up displays

You are contradict terms of task, stated by yourself.

CB> all the technicians ... need to retrain to design anti-collision
CB> pattern-recognition systems and automated friend-or-foe decision
CB> systems, because believe me *nobody* is going to buy your android
CB> solution.

In my proposal (SQL5), these systems are proposed as part of android.
And even nobody is going to offer android without this implicit systems.



Dmitry Turin
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