Re: Application logic and Business logic

From: Alfredo Novoa (alfredo_novoa_at_hotmail.com)
Date: 02/28/05 

Date: Mon, 28 Feb 2005 18:37:37 +0100

On 28 Feb 2005 15:42:01 +0000, Patrick May <pjm@spe.com> wrote:

> The business logic concepts I enumerated are at a
>different level of abstraction from the implementation-specific
>database constraints.

Database constraints are purely logical concepts. They could not be
any other thing.

But you can implement database constraints in many ways.

One of the worst ways is to implement them on the applications using
procedural code, and that is what most (if not all) OOA/D books teach.

> Entities, rules, procedures, and processes can
>be implemented in any number of ways.

Agreed, and the best way is to implement them declaratively using a
good DBMS.

> It is the concepts that are
>important in the context of this discussion, not one way of specifying
>those concepts.

A database constraint is a rule and not a way to specify a rule.

> Similarly, application logic is not limited to presentation logic
>except in simple CRUD systems.

Application logic is not limited to presentation and communication
logic except in well designed systems which are very rare.

>> OOA/D is not aware of that there are specialized systems intended to
>> manage the business logic freeing the applications from such task.
>>
>> These systems are called DBMSs.
>
> OOA/D isn't aware of anything -- it's just a set of techniques
>for developing software.

A fuzzy set of techniques that often includes very bad techniques. One
of the most popular OOA/D techiques is to implement DBMSless systems.

> However, some of the best developers I've
>had the pleasure of working with have extensive experience and
>expertise with both OO and relational technology.

Relational technology is not available.

> They know, for
>example, that DBMSs are one way to manage some types of business
>logic.

DBMSs are THE WAY to manage business logic. If you don't know that
then you don't know what a DBMS really is.

To manage any business logic on the applications is a big design
fault.

> They also know that one size doesn't fit all, so they use the
>appropriate tool for the job.

Decent developement tools don't exist and we have to deal with very
poor tools.

It is true that sometimes we are forced to corrupt the design due to
the tool's flaws, but we are corrupting the design anyway.

>
>> I don't know any programmer who knows what a DBMS really is :-(
>
> Perhaps you need to work with people who have experience in more
>than one paradigm.

I don't need to work with more people with a lot of experience making
poor jobs, what I need is to work with people who knows the
theoretical foundations of the profession, but they are really hard to
find.

Regards