Re: A working document

> On Fri, 28 Dec 2001, Cezary Zielinski wrote:
>
> [... ``component image'' vs ``component interface''...]
> > > Why use another term when the whole computer science world uses
> > > ``interface'' as the term to represent the view that a component/class
> > > offers to the outside world? ``Interface'' can be used with both
> > > components and classes; it covers both data encapsulation as
> > > ``methods''.
> >
> > To me an interface is something between two faces - a kind of a
go-between.
> > An image is something that is internal to a component. It is a data
> > structure ineternaly representing inside a component A another component
B.
> > It is a representation (obviously simplified) of component B inside
> > component A. This data structure has to get its contents from outside
the
> > component A. It gets this contents from component B through some kind of
an
> > interface between them.
> > Thus two different names are needed.
> >
> This local representation of the interface of another component is
> called a ``proxy'' in computer science. The proxy is one of the
> best-documented software patterns around, so I would think _very_ hard
> before replacing its name by something else :-)
>
To me a proxy is something that is external to a component - an image is
internal. Examples. A proxy server is a server that stands in for another
server to diminish its work-load. It services incomming requests instead of
the otherwise overloaded server. It is external both to the "overloaded"
server and to the requesters of the service. In QNX a proxy is a
quasi-process which is associated with  a proper process. Whenever someone
wants to signal the proper process of something he kicks the proxy. Thus the
notifier and the proper process are external to the proxy. A proxy is a
stand-in who acts in the name of someone. The image is simply a data
structure representing some properties of the component B. An image is
passive, a proxy is active. I think that I would rather prefer "interface"
than "proxy" in our case, although both don't suit me.
Cezary



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