[sc34wg3] One subject per role typing topic

Robert Barta rho at devc.at
Mon Nov 9 06:02:08 EST 2009

On Mon, Nov 09, 2009 at 03:06:00AM +0100, Xuân Baldauf wrote:
> (Example 2)
>     drive(driver: Paul, from: Amsterdam, to: Rotterdam)
>     walk(walker: Paul, from: Amsterdam, to: Rotterdam)
>     ride_bike(bike_rider: Paul, from: Amsterdam, to: Rotterdam)

> (Example 3)
>     drive(driver: Paul, driving_from: Amsterdam, driving_to: Rotterdam)
>     walk(walker: Paul, walking_from: Amsterdam, walking_to: Rotterdam)
>     ride_bike(bike_rider: Paul, riding_bike_from: Amsterdam,
>     riding_bike_to: Rotterdam)

> So, it seems, the question here is:
>    1. whether the role type topic on its own (e.g. the "who" topic)
>       already disambiguates the role, or
>    2. whether the role type topic _together_ with the association type
>       topic only disambiguates the role.
> Is this the correct question?

Maybe not. I would ask: 

   "Is the combination of roletypes sufficiently discriminant to
    characterize the relationship?"

Or, equivalently,

   "is the association type _just a name_ for the combination of
   roletypes?". I.e. assoctypes are a redundant information (for the
   wet robots).

In that light, Example 2 would be proper modelling. And that ...

> As "drive", "walk" and "ride_balk" are all kinds of "locomotion", and
> as, for locomotion, the role types "from" and "to" are sufficiently well
> defined, I do not see (from a software-engineering "reuse what you can
> reuse" point of view) why it is wrong to plainly re-use the "from" and
> "to" role type topics.

... would also have room for reuse.


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