Re: Securing type extensions

[Georg Bauhaus <rm.dash-bauhaus@futureapps.de>]

On 16.09.10 09:47, Dmitry A. Kazakov wrote:

>> Certainly, and a "plan" suffices as an example, if you agree
>> that perfect technical specifications of what (again, just for the
>> sake of an example) a type writer expects an extension writer to
>> do are not always possible. (Which I understand you do.)
> 
> That is not the type writer.

Party X made a library, L, of O-O types, abstract or not.
Party Y extends a type in L, say T

I'm talking about how X and Y can trust each other before
X licenses the library and before Y writes an extension.
Both parties did not co-operate before making L and wishing
to extend L.T, respectively.  It must be done now, from
what is there.

What technical factors of a language's type extension mechanism
will likely make X and Y be more confident that nothing will
go wrong?

>> The issue is related to trust, and to type extension, and it is an
>> existing challenge.
>> Call it poor design on the part of Python framework writers, if that
>> is what it seems to be.   But since the framework exists as a foundation
>> for real software, it does affect multi-party work. We can't always
>> control the parent types, and must see if we can find it trustworthy.
> 
> and the point is? 

The point is to fathom the dark waters of software development
from multiple components, of possibly closed source:
Is there anything in Ada that acts like a flash light when
compared to more dynamic languages? Facilities of Ada that makes
one feel more secure when extending a type?

(You remember the story often told about Roman bridge builders
having to stand under their new bridge on opening day. Just to
illustrate trust.)


> The way you described it, trust has no physical meaning.

When you sign a contract with your name, then this is quite physical.
When you pay, or don't pay, this is easily measured.

> It is a
> psychological phenomenon, not a subject of CS and SW engineering.

Psychology, politics, ambition and money are undoubtably parts of
SW engineering, steering the decisions. They are essential to
engineering in general.

This famous rocket did not have an O-ring suitable for the range of
temperatures, they say, and then it exploded.  There had been some
protest before the parts were composed to form the rocket. An example
showing that engineering is not just about technical formulas.


Georg