Re: BOOLEAN RELATIONSHIPS: HARD QUESTION

On Sun, 13 Jun 2004 16:50:26 GMT in comp.databases.theory, "Jacopo" <jacopols_at_libero.it> wrote:

>I need to create a database for my company. We build machines and so we have
>a part list of the components.
>I have created a model of the machine in which there is a list of components
>to be filled in order to complete the design scheme.
>Every machine will be composed by:
>1 mandatory element of type "A" among the entire list of A type items
>1 mandatory element of type "B" among the entire list of B type items
>4 mandatory element of type "C" among the entire list of C type items
>N optional element of type "D" among the entire list of D type items
>
>The problem is this. When you choose a specific element to fill the type "A"
>box you can't then choose among all the items of list B to fill the type B
>box but among those B elements that matches the selected A items.
>As well the type C is influenced by the previous choices but in this case
>the list must be differently selected for any combination of the chosen A
>and B items.
>The optional elements on the other side can be present or not, according to
>the selected A, B, C items or to a combination of them all.
>
>The problem is creating a solid model of relationships in order to let the
>user select among the only items that matches the previous ones.
>Definitely I don't want to create rules into the source code.
>The idea is giving them a mask in which, when they create a new item, they
>can link it with OR, AND, NOT, XOR, ecc. relationship.
>The problem for me is saving these rules. If just one "AND" relationship
>between two items was allowed a new table with matching couples would be
>enough, but in this case I should be able to implement a rule like:
>
>If you choose the item A38 in A AND B15 in B AND NOT C44 in C, then you
>can select the optional element among this list.

You have a set of allowed combinations of elements A, B, C: first table. Given this list, you then have combinations that allow or disallow option D. Whether you keep the all the allowed or just the disallowed combinations for each D is up to you: second table.

You can retrieve all the A options with a select distinct, B options similarly with the given A selected, likewise C given A and B. Once you have each C selection, you can store each selected combination. Given the four selected A, B, C combinations, you can retrieve the D options that either meet all the allowed combination criteria, or are not rejected by disallowed combination criteria.

Spreadsheets are ideal for creating, communicating, and validating this kind of base combinatorial data, and if you can export in tab delimited or CSV format and import that format into the database, quick turnaround on data loading and query testing.

-- 
Thanks. Take care, Brian Inglis 	Calgary, Alberta, Canada

Brian.Inglis_at_CSi.com 	(Brian dot Inglis at SystematicSw dot ab dot ca)
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