Need Global Modifier "at( at: start, etc. )"

at( at: start | at: end | at: invariant | at: variant )

Semantically this give Temporal Aspect to any specified value.

at: start - is an initial value
at: end - is a target value
at: invariant - is a continuous value
at: variant - is a series of values that are specified by an 
external file that has a time series (i.e. speed profile, acceleration profile, s-distance profile along a route)

IMPORTANT: BY Specifying this once as a Global modifier in an action, all other modifiers are implicated / affected.