Re: [BLACKBOX] Questions about inheritance

From: [at]} <Wojtek>
Date: Sun, 13 Mar 2011 12:59:26 -0400

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> I am now with CP for some years, but I never had to use OO features.
> Creating clean modules and applying classes to get abstract data
> types was sufficient for my projects in the past.

If it was sufficient till now, it will probably suffice in future. The
point is, that you have conditioned yourself to think in a certain way. It
worked for your project for years. Why do you want to change your way of
thinking, if it worked over the years?

> It's about process control and deals with automatic test equipment.

So it is complex, demanding, and mission-critical. Not a good place to
learn and to exercise. Learning and experimenting is best done with small
projects. The lessons must take time to sink in and to get into the mental
background. After a while the lessons will look obvious. Only then the new
methods can be applied to larger projects.

Working on a new, demanding project and trying to apply new, demanding
approaches at the same time is likely to lead to a disaster.


> The big picture of the technical process to be controlled is always
> the same. But in reality there are some different types of machines,
> because they have different number and type of hardware equipment,
> different types of control algorithms and different types of calls to
> a relational data base for retrieving data about the parts to be
> tested automatically and for storing the results of the tests
> respectively.

The problem with this kind of design is that you will be trying to outline
a system, which has not been developed yet (top-bottom approach). You will
be trying to guess ahead of time the facilities, which you will need
later. In all likelihood, you will guess sort of righ, but not exactly
right. This will lead to iterative work: down the road you will discover,
that initial guesses were not quite righ, and you will have to revisit the
assumptions and rewrite large portions of your software. After two or
three such iterations you will get exhausted.

In my opinion, OO frameworks such as BB itself were never developed this
way. BB was not written on the first attempt. There were predecessors,
such as the Oberon System, Gadgets, Ethos, etc. At some points the
experience from these prototypes was refined in the form of the OO
framework Oberon/F, which then became BlackBox. Therefore, the amount of
top-down guessing was in fact pretty minimal, because most of the design
choices have been tried before.

> For me as a novice in object oriented design this project seems to
> require a small framework which is adaptable to the technical
> hardware at hand. Unfortunately I don't know when to apply which of
> all these interesting OO concepts and how to do this.

My advice is "don't". Stick with what you know. After you achieve a
working system and use it for a while, its patterns will become clear in
your mind. At that point you may choose to apply OO concepts to simplify
your software, which you will then know and understand. The OO rework of a
well understood project will not require the guesswork, which it would
require now, when you are working on a new project.

These remarks come from my own experience. Your experience may be
different, so please take them with the usual grain of salt.

Wojtek

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Received on Sun Mar 13 2011 - 17:59:26 UTC