Amedeo,

What you have here is a design pattern known as a "Bill of Material." It can be quite involved implementing a "Bill of Material" and there are different types of these to consider. The main two are "Engineering Bill of Material" and "Manufacturing Bill of Material."

Here is a short non-technical explanation of a "Bill of Material:"

http://www.npd-solutions.com/bom.html

As you suspect this does require a "reflexive" many-to-many relationship. It also requires a "recursive" validation to make sure that no subassemblies ever contain the "root" product.

You will need an exposed join table (so no flattening of the many-to- many can be used). At minimum the join table will need an "exposed" attribute to indicate the quantity of each component part used in the product being built.

Part    <---->>  ComponentAssembly    <<---- Part

On Feb 7, 2006, at 6:31 AM, Amedeo Mantica wrote:

Hi, a question... how to implement this:

Products entity...

some product can be related to many other products...

then I need to join in many-to-many the same entity...

any suggestion?

thanks
Amedeo
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