Re: How to? Writeable from a readable?

["John R. Strohm" <strohm@airmail.net>]

Maybe I'm way out in left field here.

In capability-based operating system terms, it sounds as though you are
trying to take a read-only capability and amplify it into a read-write
capability.  Every capability system I ever saw was specifically designed to
prevent you from doing precisely that: if the owner of the object wanted you
to have read-write access to the, he would have granted you a read-write
capability for the object in the first place.

What I think you want to do is go back to the original system, structure it
as a read-write object, and then make a read-only view of it that you give
out to the world.  Only the ones who really have a legitimate need for
read-write access get the read-write capability.

"chris.danx" <spamoff.danx@ntlworld.com> wrote in message
news:3T2S9.721$GU4.33144@newsfep1-gui.server.ntli.net...
> Hi,
>
> How can you resolve the following problem?  Let's suppose you have a
> tagged type readable_x say, which only allows you read access to the
> data in it, and you want to extend it with a new tagged type writeable_x
> which allows you read and write access to data.  How can you do this?
>
>
> The problem as I see it, is that if you make the data in readable_x
> private you can't extend and modify it in the extended type, but if you
> make it public anyone can modify the data anyway.  Is there a way around
> this problem (I want to allow a writeable wherever a readable is
allowed!)?
>
>
> Cheers,
> Danx
> --
> for personal replies change spamoff to chris
>