Grasping the concept of Classes & Categories

Alan L. Lovejoy sourcery at comcast.net
Sat Jun 18 20:51:29 UTC 2005


Daniel:

You might want to look into "subjectivity." Here' a link to get you started:
http://www.laputan.org/reflection/subject94.html

--Alan

-----Original Message-----
From: squeak-dev-bounces at lists.squeakfoundation.org
[mailto:squeak-dev-bounces at lists.squeakfoundation.org] On Behalf Of Daniel
Salama
Sent: Friday, June 17, 2005 10:26 AM
To: chris at funkyobjects.org; The general-purpose Squeak developers list
Subject: Re: Grasping the concept of Classes & Categories

Chris,

That's a very interesting perspective. The thought crossed my mind,  
but then I thought of another "issue" which is what prompted me to  
ask the question to the list.

Originally I thought I could simply just run an image for each of  
these specialized applications. For example, one could be a Customer  
Relationship Management system, while the other is a Medical Billing  
system. Both systems have different views of what a Customer is and  
it would make sense to run them in separate images.

However, given my limited resources for hardware (mainly), I wasn't  
sure if I could, efficiently, run two Squeak images, each with  
Seaside listening on different ports and both front-ended by Apache  
on a single machine. I wasn't sure how two images could run on the  
same machine in terms of performance, processes, memory, etc.  
Assuming these would run on a dual-Xeon machine with 2GB RAM, would  
that be feasible?

To some degree, I guess the question will depend on the traffic load  
on the machine, but I would guesstimate that, for example, the CRM  
system would handle about 10000 contacts a day (by contact I mean  
customer record inquiries, or logging call attempts, etc) and maybe  
about 500 medical bill records per day. If anyone has some experience  
in these industries, you can guesstimate some sort of traffic load.

I don't k now if I'm being too vague or worrying too much about  
something that hasn't been materialized yet. I just like to plan ahead.

Thanks,
Daniel

On Jun 17, 2005, at 11:50 AM, Chris Muller wrote:

>> I have two applications that both need a class Customer. However, one
>> of the application requires that class Customer have a set of
>> attributes and methods very different from the second application who
>> uses the class Customer for a totally different industry.
>>
>
> Hi Daniel, for me, the key to the answer to your question is the  
> phrase
> "totally different industry."  If this is true, it seems there  
> would be little
> chance that the Customers would need to be in the same running  
> image, nor would
> they need to be developed together.
>
> Therefore I wouldn't worry too much about trying to factor the two  
> Customer
> classes into a single, grand Customer superclass, if it won't ever be
> commingled in practice.  In fact, doing so could potentially  
> increase cost.
> For example, the two groups of developers may have their own ideas  
> about what
> belongs in the generic superclass Customer.  So then you have  
> developers
> spending time reconciling code by two completely disparate industries.
>
> Even if theres a remote chance of the two programs needing to co- 
> exist in an
> image, you can use refactoring-tools to meld the code at that  
> time.  But keep
> it simpler in the meantime.  Remember, if you can solve the problem  
> of ultimate
> malleability of software, you no longer need to worry about up- 
> front planning
> of "ultimate" classes..  We still need a balance of both, but I  
> believe the
> future is in the former.
>
> That's my view, anyhow..
>
>  - Chris
>
>





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