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If you want to describe 1:many relationship, you can do so using
element-subelement, for example, if there is a 1:many from A to B in your
example, say it in your DTD as:
root -> B*
B -> (B.1, B.2, A*)
A -> (A.1, A.2)
In the above the relationship from B to A is not captured, however.
Also, if you would like to capture many:many relationships or
relationships such as B to A, then we need to be able to specify foreign
keys, which are not possible using DTDs alone. Rather the current
constraint specification (used as the basis for specifying relationships
in databases and mostly will be used in XML) has not matured fully as yet,
and hence there exist limitations.
cheers and regards - murali.
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On 31 Jul 2002, Mudita Singhal wrote:
> Hello all,
>
> I am new to this group and so might be asking a question which
> might ahve already been answered, or is very simple.Sorry for
> that.
>
> If we have to make a DTD for a database with 2 tables, say A and
> B.The attributes of the tables are as under:
>
>
> Table A
> A.1(PRIMARY KEY)
> A.2
> A.3(FORIEGN KEY TO TABLE B)
>
> Table B
> B.1(PRIMARY KEY)
> B.2(foriegn key to table A)
>
> Now can anyone guide me on how to write a simple DTD for
> this.Means , do we have to declare a content type declaration for
> the forign keys also??IF not then how do we write the XML document
> for this?
>
> secondly How to impose the many-to-many and one-to-many
> relationships?
>
> Thanks
> Mudita
>
>
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- References:
- Doubt
- From: "Mudita Singhal" <msinghal3@rediffmail.com>
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