Re: Architecture ideas for n-tier app with diff backends

Charles McDonald wrote:

> Hi Guys
>
> I have a question regarding the seperation between the Business (BOL)
> and Data (DSL) layers and where what should go.
>
> Let us assume that we have a Customer and CustomerOrders tables.
> Let the BOLCustomer and BOLCustomerOrders be the business objects and
> DSLCustomer and DSLCustomerOrders be the Data objects. Now if we wish to
> have a method in BOLCustomer to retrieve all the orders for a particular
> customer would the processing be in the BOL or the Data layer?
>
> ie: Would the data layer simply contain Add, Delete and Update methods
> and the BOL would use these methods to build a list of CustomerOrders or
> would the list be built in the Data layer.
>
> My impression is to use have only the atomic (?) -add, delete & update -
> methods in the DSL and build the list using these methods in the BOL.

You would presumably need at least a 'find' method in the DSL, which would naturally allow a multi-entry return, making it your 'list' function as well. This is as 'atomic' as an insert or delete, and the correct place for it.

   I believe you are mixing apples-and-oranges with the BOL-DSL nomenclature. Your business objects are logically distinct entities, whose physical implementation includes the DSL. The business object IMHO has an implementation which spans the class, it's DBMS access, the DBMS contents, and the DBMS-enforced refer- ential integrity, including any triggers and indexes on the DBMS tables.

Joe Weinstein at BEA, the home of WebLogic --
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