Re: What is this model technique called

In message <2981867.1055186932_at_dbforums.com>, jimv <member30950_at_dbforums.com> writes
>
>I have been reading this thread with interest, since I was thinking that
>EAV would work well for my application. It does seem to be quite
>popular for storing medical records, as can be seen by a quick google
>search on EAV.

I've used it on occasions. I've used it when I know that the people using the database understand metadata.

>
>I am working on an inventory system. However, I can assume very little
>about the type of data that is associated with inventory items. I know
>that every inventory item will have a manufacturer, model, and serial
>number, but I can't assume anything else.
>
>For example, a monitor has a size and refresh rate, a computer has a
>certain size of memory and hardrive, etc.
>
>If I don't store these as name/value pairs, how can I store them?
>One big string doesn't seem like a very good idea. I need to be
>able to perform stock counts too, so that I end up with a list
>saying, for example:

You can use subentities if you know that every item will fall into one of a limited range of types, and you know what all of those types are.

The EAV system (or a version of it) predates relational algebra by a century or two. Library systems assign attributes (classes) to books. Sometimes a book arrives that doesn't fit in any existing class so the librarian has to create a new one. The new class then gets communicated to every other librarian.

-- 
Bernard Peek
bap_at_shrdlu.com
www.diversebooks.com: SF & Computing book reviews and more.....

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