Why Timed Sequence Diagrams Require Three-Event Semantics

Abstract

Abstract. STAIRS is an approach to the compositional development of sequence diagrams supporting the specification of mandatory as well as potential behavior. In order to express the necessary distinction between black-box and glass-box refinement, an extension of the semantic framework with three event messages is introduced. A concrete syntax is also proposed. The proposed extension is especially useful when describing time constraints. The resulting approach, referred to as Timed STAIRS, is formally underpinned by denotational trace semantics. A trace is a sequence of three kinds of events: events for transmission, reception and consumption. We argue that such traces give the necessary expressiveness to capture the standard UML interpretation of sequence diagrams as well as the black-box interpretation found in classical formal methods.

Stepwise refinement of sequence diagrams with soft real-time constraints

“…STAIRS assigns formal semantics to sequence diagrams and defines refinement relations similar to the ones presented here. Time is introduced in STAIRS in [6]. An operational semantics for STAIRS is given in [16,17], equivalent to the denotational one.…”

“…We refer to this approach as probabilistic STAIRS, or pSTAIRS. The approach is based on STAIRS [4,5,6], and extends STAIRS with the expressive power to capture soft real-time constraints as well as other probabilistic constraints. This is achieved through extensions to ordinary sequence diagram notation that are, in our opinion, small and intuitive.…”

Time Exceptions in Sequence Diagrams

“…TimedSTAIRS [4] is an approach to the compositional development of timed sequence diagrams. With time constraints, we argue that it is important to know whether a given constraint applies to the reception or the consumption of the message.…”

“…With time constraints, we argue that it is important to know whether a given constraint applies to the reception or the consumption of the message. Hence, in [4] we introduce a three-event semantics for timed sequence diagrams. In some cases, the time constraint should apply to the receiving of the message, while it in other situations should apply to the consumption.…”

“…In order to make a graphical distinction between reception and consumption, [4] uses a double arrow for reception and the standard single arrow for consumption. We will follow this convention in our examples.…”