[Zope-Coders] Re: "Anonymous" role is pretty bizarre?

[Tres Seaver]

Chris McDonough wrote:
> On Mon, 2004-03-22 at 12:05, Chris Withers wrote:
> 
>>Chris McDonough wrote:
>>
>>>FWIW, I think the "Anonymous" role is pretty bizarre, 
>>
>>How so?
> 
> 
> It's the only role that is meant to apply to a single system user and
> one of two (with Authenticated) which cannot be granted to normal
> users.  Think about it.

Both of those roles are logically groups to whom permissions are 
assigned:  the 'Anonymous' role is actually an 'Everyone' group, with 
special-cased optimizations based on that fact littered throughout the 
code.  The 'Authenticated' role is really a group consisting of 
'Everyone' minus the one-and-only 'Anonymous User'.

Getting the terminology straght is hard, especially after we have all 
bent our brains not to fight with Zope's machinery.

   'Principal' -- an identifiable user, or group of users, to whom
     privileges are granted.

   'User' -- a single principal, associated with a request.  Each request
     has exactly *one* user, who may be the "nobody" user.

   'Group' -- a collection of principals (perhaps including other
     groups!)

   'Role' -- an abstraction representing the granting of one or more
     privileges to a given principal.

   'Permission' -- a single privilege, defined by the software developer.

   'Permission set' -- a rolled-up set of permissions, designed to be
     presented as a single chunk in the UI.

<pre class="sop-to-mail-readers-with-non-monospace-fonts">

       +---> Principal<-------->Role<-------->Privilege <-------+
       |  *      ^     *      *      *      *     ^      *      |
       |        /_\                              /_\            |
       |         |                                |             |
       |         |                                |             |
       |     +---+----+                    +------+------+      |
       |     |        |                    |             |      |
       +-<>Group    User            Permission  PermissionSet<>-+

</pre>

In Zope, roles are often warped into either 'groups' or 'permission 
sets', when in fact they are a third thing altogether (this confusion 
arises largely because classic Zope2 has neither groups nor permission 
sets).

Zope3 has already disentangled this mess to some extent;  Jim has 
expressed some hope that we might be able to migrate its cleaner model 
back into some version of Zope2.  Zope3 does allow for grants of 
privileges "directly" to principals, with no explicit role;  it makes 
this choice because many people find such grants "natural".  I would 
prefer to model that grant as being made a an "eponymous" role, but 
maybe I am just fussy. ;)

OTOH, the "Anonymous" role which this sub-thread is about is almost such 
a role, so perhaps not.

Tres.
-- 
===============================================================
Tres Seaver                                tseaver at zope.com
Zope Corporation      "Zope Dealers"       http://www.zope.com