(responding to Alexandre Sampaio)

> I�ve two questions about actors.

I agree with Les that there are no answers that are correct for
everybody.  This depends to some degree whether you want to be
pedantically correct about UML or whether you want to be as
clear as possible in what you are saying.

> 1.    Must we have only one actor initiating the UC? If I have two 
> actors initiating the UC, like �kiosk customer� and �schedule 
> administrator� that initializes the same UC, �View game schedule� 
> (the flow does not change for both), must I generate a more abstract 
> parent actor?

For each use case instantiation, only one Actor can instantiate.  However,
this Actor is not necessarily always of the same class.  If you want to
be pedantically correct, then there will be some common subset
of behaviours of 'kiosk customer' and 'schedule administrator'
that qualify these astors to instantiate this use case, and it _might_
aid future extension of the system if this was separated out into
a common superclass of these named actors.  OTOH doing this for
all such occurrences may result in a multiple inheritance hierarchy,
and some people find this comparatively difficult to comprehend.

I would find it perfectly adequate in the use case diagram for this
use case to link the two named initiating actors with a note saying
"XOR" or some other way of indicating one, but not both, instantiate
each use case of this class.

> 2.    May I have an actor that does not interact with an UC? For 
> example, I have two actors, CIC and PV, these actors have a parent 
> actor called �CA�. If the actor �CA� does not interact with an UC, is 
> this a valid actor? And if only the actor �CA� interact with an UC, 
> are �CIC� and �PV� valid actors?

There are few reasons why you might want to do this, but in
general I'd agree with Les and say don't do it.  Remember,
the underlying purpose of an Actor in UML is to document the 
interaction between the system and a particular class of user
of the system.  If there is no interaction, the actor tends to be
superfluous.  There are, however, a few cases where showing
such actors can, nevertheless, convey useful information
about the system and its context, so I would say, if adding 
these extra actors does indeed convey useful information,
go ahead and add them.

Paul Oldfield

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
www.aptprocess.com

any opinions expressed herein are not necessarily those of
Mentors of Cally or the Appropriate Process Movement
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

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