Re: How to create a DBMS from scratch?

"oblomov" <spam_at_oblomov.org> wrote in message news:20021128043026.50341077.spam_at_oblomov.org...
> On 28 Nov 2002 03:01:15 GMT
> Christopher Browne <cbbrowne_at_acm.org> wrote:
>
> > In the last exciting episode, Andy Dingley <dingbat_at_codesmiths.com>
wrote::
> > > On Mon, 25 Nov 2002 12:45:29 +0000, Rob Tweed
> > > <rtweed_at_imtcons.demon.co.uk> wrote:
> > >
> > >>Its interesting the way XML has brought back new life into the old
> > >>hierarchical databases,
> > >
> > > Interesting, but not a good thing.
> > >
> > > This commonality between XML and hierarchical DB's isn't a validation
> > > of the DB, more a condemnation of XML's rigidly tree-structured data
> > > model.
> >
> > The fact that certain varieties of hierarchical queries are not
> > particularly convenient in SQL is a bit of condemnation thereof.
> >
> > You tend to have two choices:
> >
> > a) You iterate through the tree, an SQL query for each node, or
> > b) Go with some cleverness ala the "Celko nested sets" approach.
>
> Why not just run an LDAP and an RDB at the same time? It's not impossible
in any way. Keep heirchial design in heirachial persistency and cross-referenced relations in relation-style persistency.
>
> Or if you ask me, get an OODB and skip the mapping-layers so it's up to
you and your design.
>
>
>
> karl

Yes use LDAP for XML. This book chapter does a nice comparison of several approaches (RDB, OODB, Native XML, LDAP):

C. Schmauch and T. Fellhauer (2003) A comparison of database approaches for storing XML documents. In: XML Data Management: Native XML and XML-Enabled Database Systems, A.B. Chaudhri, A. Rashid and R. Zicari (eds.), Addison-Wesley, Reading, Massachusetts, 2003. To appear. http://www.aw.com/catalog/academic/product/1,4096,0201844524,00.html

Whilst there are a number of documented approaches for storing XML in an RDB (e.g. see the book by Graves), Celko's nested sets has been used successfully by my colleague, Dr. Richard Edwards. The code can be downloaded from sourceforge:

http://minx.sourceforge.net/

Richard also has a nice chapter in the above book mentioned :-)

vr

--
Akmal B. Chaudhri
Zone Editor, Special Projects (Eclipse, Grid, Web Services)
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