RE: Top down or bottom up

[Phillip Hallam-Baker <pbaker@verisign.com>]

> Well, I'll bite at the bait.  Unfortunately, due to 
> circumstances beyond my
> control, I don't have as much time to write a response as I'd like.
> 
> Which use cases do you believe bottomish makes easier than 
> toppish?  

I believe that both mechanisms can meet the use cases specified.

However the use cases specified may be unrealistic in being more
abstract and simplified than practical implementations would require.

The bottomish approach would provide more flexibility should 
practical experience prove that the original use case analysis
was wrong.

> One of the ideas that these discussions and proposals seems 
> to have brought
> is a scope discussions about whether we are defining a framework for
> assertions or assertions themselves? 

If we adopt a layered design methodology we do both.


> I think one of your  objections to
> toppish typing is that it locks implementations into a 
> particular model. But isn't that what we want? 

My end goal is to satisfy as many customers as possible, thus
causing all our stock options to increase in value.

I have no interest in attempting to lock anyone into anything.

At a recent workshop Dave Clarke ripped into certain wireless
technology on the basis that the entire range of uses had been 
designed in, the technology was designed to insist that it only 
be used as intended.

>I assert that successful standardization
> requires reduced flexibility and locking into a particular 
> model.  SOAP is a
> good example of locking users into a particular model for 
> headers, body,
> requests, responses, parameters, etc.  Java is another example.  

That is quite different. The design does not reduce functionality,
it reduces the number of means of achieving a given functionality,
a very different issue.

> The arguments that you are making, particularly to Pascal and 
> to reduced flexibility, leads me to believe that you are of the 
> weakly-typed camp, ala
> Smalltalk.  Whereas I've been a strongly-typed proponent, ala 
> Java and C++
> Would strong versus weak types be an accurate analysys of the 
> toppish versus
> bottomish typing? 

It would be a complete misrepresentation of my position.

C++ is in my view a weakly typed language. I have worked extensively
with true strongly typed languages such as Z and VDM.

The core fallacy of the Pascal 'type' system is that Wirth failled
to understand the distinction between type and representation.

> One way I'd summarize the toppish versus bottomish as specify 
> cardinalities
> or not.  

Confusion of type systems and syntax has long been considered an
error in language design.

	Phill

Phillip Hallam-Baker (E-mail).vcf