UTP12 — Rename predefined type Time to Timepoint

In UTP 1.1 there are two predefined time-related types: Time and Duration. Time is used for starting a timer (Timer::start(expre:Time)), so it represent rather a Duration. In addition, time is ambiguous, because it is not clear what time actually represents, a particular point in time or a duration of time units.

Since UTO already defines a Duration type to express a duration of time unit, Time should be renamed to Timepoint to cope with particular points in time. Concrete timepoint formats are not given by UTP.

Furthermore, Timer should offer a second start() method with the signature Timer::start(duration:Duration). The user would be able to decide whether a time should timeout at a certain point in time or after a given duration.

The RTF agreed that the UML Testing Profile should allow to set both a duration and a timepoint for a timer to expire. This is consistent with the UML simple time concepts, where a user can express TimeEvents in terms of Duration or TimeExpression. However, it is not the intention of UTP to predefine or determine the concrete format of a Timepoint or Duration. There is ongoing work within the OMG to standardize those things.
Additionally, the RTF agreed on setting a constraint how values/instances of these two primitive types have to be expressed. In order to align the imperative timer concept of UTP with the declarative one of UML simple time, instances/values for utp::Timepoint shall be expressed as utp::TimeExpression with type set to utp::Timepoint. Consequently, instances/values of utp::Duration have to be expressed as uml::Duration with type set to utp::Duration. Again, the concrete format of such a ValueExpression is not predefined and is left open to the user. Finally, the predefined Timer interface of UTP should offer operations to start a Timer with either a Duration or Timepoint for expiration.