Live Sequence Charts (LSC) extend Message Sequence Charts (MSC), mainly by distinguishing possible from necessary behavior. They thus enable the specification of rich multi-modal scenario-based properties, such as mandatory, possible and forbidden scenarios. The sequence diagrams of UML 2.0 enrich those of previous versions of UML by two new operators, assert and negate, for specifying required and forbidden behaviors, which appear to have been inspired by LSC. The UML 2.0 semantics of sequence diagrams, however, being based on pairs of valid and invalid sets of traces, is inadequate, and prevents the new operators from being used effectively.We propose an extension of, and a different semantics for this UML language-Modal Sequence Diagrams (MSD)-based on the universal/existential modal semantics of LSC. In particular, in MSD assert and negate are really modalities, not operators. We define MSD as a UML 2.0 profile, thus paving the way to apply formal verification, synthesis, and scenario-based execution techniques from LSC to the mainstream UML standard.

Reactive synthesis is an automated procedure to obtain a correct-by-construction reactive system from its temporal logic specification. Two of the main challenges in bringing reactive synthesis to software engineering practice are its very high worst-case complexity-for linear temporal logic (LTL) it is double exponential in the length of the formula, and the difficulty of writing declarative specifications using basic LTL operators. To address the first challenge, Piterman et al. have suggested the General Reactivity of Rank 1 (GR(1)) fragment of LTL, which has an efficient polynomial time symbolic synthesis algorithm. To address the second challenge, Dwyer et al. have identified 55 LTL specification patterns, which are common in industrial specifications and make writing specifications easier. In this work we show that almost all of the 55 LTL specification patterns identified by Dwyer et al. can be expressed as assumptions and guarantees in the GR(1) fragment of LTL. Specifically, we present an automated, sound and complete translation of the patterns to the GR(1) form, which effectively results in an efficient reactive synthesis procedure for any specification that is written using the patterns. We have validated the correctness of the catalog of GR(1) templates we have created. The work is implemented in our reactive synthesis environment. It provides positive, promising evidence, for the potential feasibility of using reactive synthesis in practice.

Abstract. Class diagrams (CDs), which specify classes and the relationships between them, are widely used for modeling the structure of object-oriented systems. As models, programs, and systems evolve over time, during the development lifecycle and beyond it, effective change management is a major challenge in software development, which has attracted much research efforts in recent years. In this paper we present cddiff , a semantic diff operator for CDs. Unlike most existing approaches to model comparison, which compare the concrete or the abstract syntax of two given diagrams and output a list of syntactical changes or edit operations, cddiff considers the semantics of the diagrams at hand and outputs a set of diff witnesses, each of which is an object model that is possible in the first CD and is not possible in the second. We motivate the use of cddiff , formally define it, and show how it is computed. The computation is based on a reduction to Alloy. The work is implemented in a prototype Eclipse plug-in. Examples show the unique contribution of our approach to the state-of-the-art in version comparison and evolution analysis.

Specification mining is a dynamic analysis process aimed at automatically inferring suggested specifications of a program from its execution traces. We describe a novel method, framework, and tool, for mining inter-object scenario-based specifications in the form of a UML2-compliant variant of Damm and Harel's Live Sequence Charts (LSC). LSC extends the classical partial order semantics of sequence diagrams with temporal liveness and symbolic class level lifelines, in order to generate compact and expressive specifications. The output of our algorithm is a sound and complete set of statistically significant LSCs (i.e., satisfying given thresholds of support and confidence), mined from an input execution trace. We locate statistically significant LSCs by exploring the search space of possible LSCs and checking for their statistical significance. In addition, we use an effective search space pruning strategy, specifically adapted to LSCs, which enables efficient mining of scenarios of arbitrary size. We demonstrate and evaluate the utility of our work in mining informative specifications using a case study on Jeti, a popular, full featured messaging application.