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.
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