[cap-talk] Don't understand capabilities

[Valerio Bellizzomi]

On 30/10/2006, at 6.55, Rob J Meijer wrote:

>On Sat, 28 Oct 2006, Marcus Brinkmann wrote:
>
>> >
>> > Marcus Brinkmann wrote:
>> > > At Wed, 25 Oct 2006 11:19:38 -0700,
>> > > Jed at Webstart <donnelley1 at webstart.com> wrote:
>> > >
>> > >>If we haven't adequately conveyed that message so that somebody can
>> > >>do "much reading" on the capability concept and still not
understand
>> > >>it then I think something is seriously wrong with "our" message.
>> > >
>> > > Mmmh.  I have a gut feeling here.  Capabilities may be difficult to
>> > > understand because they are not "natural", in the sense that they
are
>> > > not a concept that comes out of human experience.
>> >
>> > They are no more or less so than "objects" in the object-oriented
>> > programming sense.
>>
>> Why do you think so?  Certainly, the human mind has a great capacity
>> to identify and abstract objects in the real world.  Furthermore,
>> "operating on an object" seems also to be a concept inherent to the
>> human mind, as the passive voice shows which is part of our language
>> (have to check with a linguist if it is universal, but it's hard to
>> imagine exceptions).
>
>But in OO programming you need pointers or references  (or capabilities)
>to 'operate' on these objects. Thus you should not look to see if the
>concept of 'objects you can operate on' is as natural as 'operating on
>objects with capabilities'.
>You should look if 'capabilities' are as natural as 'pointers' or
>'references'. In my view neither is realy natural, least of all
>pointers.

The possess of a capability gives you the full power to use it, like a key
or a badge.
Revoking a capability is like disabling a badge, you can still possess it
but it becomes unusable.

val