**Capabilities**

dan:
For an OS, you get capabilites from the kernel, or some
appropriately delegated authority (which from hereon in I
will describe as "a security service"). It's most certainly
not "we haven't thought about it yet": there are many
operating systems in use which use capabilities for security
(EROS and Amoeba come to mind).

There is more to it, namely, how are capabilities
implemented?

One method is to use unbreakable abstractions. Implement
the capability inside kernel or security service, and your
normal memory protection system should make the abstraction
unbreakable.

The other option (used in Amoeba, because it's a
distributed OS) is to use cryptography. It's slow. Enough
said.

**Mathematics**

To the Advogato amateur mathematicians: For those
interested in a more "open" MathWorld replacement, I've
registered a project on SourceForge under the working title
Principia
Mathematica. The first mailing list,
"principia-discuss" should be up in a little while. Please
add yourself if you support the idea of an open
encyclopaedic dictionary of the mathematical sciences.

There will be some interesting social and technical
challenges. The most difficult technical challenge, as I see
it, will be how to handle mathematical and diagrammatic
content with a web-based
interface in a form that's convenient for mathematicians. I
have some thoughts on this (which involve converting between
LaTeX, Lout and MathML amongst other things), but I'd like
to talk about it first.