Re: A Design Question

[Kimbro Staken <ks...@dbxmlgroup.com>]

On Monday, February 11, 2002, at 03:24 AM, Yaser Al Masri wrote:
>
> Hi,
>
> In relational databases language, tables should represent collections, 
> and records should represent documents.  But from my knowledge in design 
> strategies in RDBs, the aforementioned design if mapped into RDB it would 
> be a bad one.  The difference here is that RDBMSs use joins to relate 
> categories in categories table for example, to items in items table, 
> while most native XML databases (or at least Xindice) doesn't currently 
> support joins (or links in XML databases language), so if I want to 
> create two collections; one for categories and subcategories, and another 
> for items, I won't be able to clearly see what should look like foreign 
> key-primary key relation between the documents (indexing may help, but 
> still we don't have strict coupling between collections' documents as 
> opposed to 'views' in RDBs), and I think also we here lost the physical 
> joins available between the documents, which is one of the valuable 
> things that distinguishes native XML databases from others.
>

I'd think it's be easier to just use one collection for all documents. 
Specify which category the item is in through data within the document 
rather then through a physical structure. This also makes it easy to have 
items in more then one category or to move things around. Basically, try 
to leverage the semi-structured nature of the database and XML to simplify 
the physical database design and avoid the need for joins.

Another alternative is to push the join concept into the client. It sounds 
like you could get away with retrieving a category description with one 
read and then all documents in that category with a second. There's no 
real need to do that within the database since you're retrieving data in 
larger chunks. i.e. in a RDBMS your item description would probably be 
spread across many tables that need to be joined together, in XML it's 
probably just one document.

>
> Can anybody help me in this argument....thank you.
>
>
>

>

>
> MSN Photos is the easiest way to share and print your photos: Click Here
>
Kimbro Staken
XML Database Software, Consulting and Writing
http://www.xmldatabases.org/