[glue-wg] Capacity representation

[Burke, S (Stephen)]

Paul Millar [mailto:paul.millar at desy.de] said:
> As a counter-example, the same is true for the CE-SE-Bind (in 
> whatever form it 
> might take).  This leads no independent existence from the CE 
> and SE it connects, yet is represented as an object.

I'll reply to the rest tomorrow, but just on this since I thought of
another example: consider a coffee mug. That has a handle, and in
principle I could consider it as a separate object (I could break it
off), although for any practical purpose it's only useful when attached
to the mug. Now consider that the mug has a capacity (I can put 300 ml
of coffee in it). In that case it clearly makes no sense to consider the
capacity as having an independent existence of any kind, there's no way
to detach it from the mug. ("I've often seen a cat without a grin,"
thought Alice; "but a grin without a cat! It's the most curious thing I
ever saw in all my life!")

  Similarly with the MappingPolicy: if the mug belongs to me that's an
access rule, and although other things may belong to me the specific
"instance" of belonging that applies to the mug is not transferrable or
shareable - if I own two mugs and give one away it doesn't affect the
other one (rules and capacities may be equal but that doesn't make them
identical).

  In the case of the CESEBind there is something real underneath, some
kind of network connection and/or firewall rules and/or policies about
which protocols are allowed where. It might well be pointless to publish
such information without relating it to a CE and an SE, but not
nonsensical (indeed in principle it's interesting to know it for a UI). 

  For that matter you could say the same about e.g. the AccessProtocol:
we wouldn't publish one independently of an SE, and indeed we can't
because it only has a LocalID. Nevertheless it does deserve to be an
object and not just an attribute of something else because it describes
a discrete part of the SE, much like the handle of a mug.

Stephen