  English language requirements are often used to specify the behavior of
complex cyber-physical systems. The process of transforming these requirements
to a formal specification language is often challenging, especially if the
specification language does not contain constructs analogous to those used in
the original requirements. For example, requirements often contain real-time
constraints, but many specification languages for model checkers have discrete
time semantics. Work in specification patterns helps to bridge these gaps,
allowing straightforward expression of common requirements patterns in formal
languages. In this work we demonstrate how we support real-time specification
patterns in the Assume Guarantee Reasoning Environment (AGREE) using observers.
We demonstrate that there are subtle challenges, not mentioned in previous
literature, to express real-time patterns accurately using observers. We then
demonstrate that these patterns are sufficient to model real-time requirements
for a real-world avionics system.
