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A major obstacle in the technology transfer agenda of behavioral analysis and design methods is the need for logics or automata to express properties for control-intensive systems. Interaction-modeling notations may offer a replacement or a complement, with a practitioner-appealing and lightweight flavor, due partly to the sub specification of intended behavior by means of scenarios. We propose a novel approach consisting of engineering a new formal notation of this sort based on a simple compact declarative semantics: VTS (visual timed event scenarios). Scenarios represent event patterns, graphically depicting conditions over traces. They predicate general system events and provide features to describe complex properties not expressible with MSC-like notations. The underlying formalism supports partial orders and real-time constraints. The problem of checking whether a timed-automaton model has a matching trace is proven decidable. On top of this kernel, we introduce a notation to state properties over all system traces: conditional scenarios, allowing engineers to describe uniquely rich connections between antecedent and consequent portions of the scenario. An undecidability result is presented for the general case of the model-checking problem over dense-time domains, to later identify a decidable-yet practically relevant-subclass, where verification is solvable by generating antiscenarios expressed in the VTS-kernel notation.