Re: What is multidatabase

I'm not sure if there is a DEFINITIVE meaning to the term 'multidatabase'. In general, it refers to a several databases (of course) which are

• independent of one another
• may be heterogeneous (different platforms, semantics, etc.)
• but whose contents can be accessed from a 'global' site

Multidatabases are generally set up from the bottom up, because the databases were created independent of one another. There are different means of getting this set up. You can simply have access to all of the databases using a query language. So it'll be up to you to put things together. Or you can set up a virtual system that looks and feels like a single database as far as access is concerned, but really, it's a virtual combination of those original databases. This is very difficult to set up because those databases are probably different in all sorts of ways. This is usually not possible to set up just like that, out of the box. I think that a few DBMS products out there have their own ways to do this. IBM has a Data Joiner, according to someone in this newsgroup. Sybase had (has?) its Jaguar CTS (or probably something newer). Oracle lets you set up links (according to someone in this newsgroup). I think these would all require some doing, nonetheless, and the assumption is that direct connection to all the databases is possible.

The worst is if they're in different platforms and direct connection is not possible due to platform differences. In this case you can use middleware like CORBA or gateways like JDBC/ODBC but it will still take some setting up. You'd have to put wrappers (translator objects) around the databases to make them talk the same language and THEN set up maybe stored procedures to handle specific sorts of queries that map down to local queries for the databases. Sounds like great fun, huh? ;-)

Try searching the Net for "TSIMMIS", "CLIO" or "ARIADNE" for more info.

venetta wrote:
>
> Hi,
>
> Can someone please explain the term multidatabase?
>
> For example, if companies 1,2,3 replicate their database to company 9,
> is this consider as multidatabase?
>
> Thank you.

Jeff Received on Thu Nov 08 2001 - 03:23:12 CET