Bikram Sengupta

A research agenda for distributed software development

In recent years, a number of business reasons have caused software development to become increasingly distributed. Remote development of software offers several advantages, but it is also fraught with challenges. In this paper, we report on our study of distributed software development that helped shape a research agenda for this field. Our study has identified four areas where important research questions need to be addressed to make distributed development more effective. These areas are: collaborative software tools, knowledge acquisition and management, testing in a distributed set-up and process and metrics issues. We present a brief summary of related research in each of these areas, and also outline open research issues.

Triggered Message Sequence Charts

This paper introduces triggered message sequence charts (TMSCs), a graphical, mathematically well-founded framework for capturing scenario-based system requirements of distributed systems. Like message sequence charts (MSCs), TMSCs are graphical depictions of scenarios, or exchanges of messages between processes in a distributed system. Unlike MSCs, however, TMSCs are equipped with a notion of trigger that permits requirements to be made conditional, a notion of partiality indicating that a scenario may be subsequently extended, and a notion of refinement for assessing whether or not a more detailed specification correctly elaborates on a less detailed one. The TMSC notation also includes a collection of composition operators allowing structure to be introduced into scenario specifications so that interactions among different scenarios may be studied. In the first part of this paper, TMSCs are introduced and their use in support of requirements modeling is illustrated via two extended examples. The second part develops the mathematical underpinnings of the language

Triggered message sequence charts

We propose an extension to Message Sequence Charts called Triggered Message Sequence Charts (TMSCs) that are intended to capture system specifications involving nondeterminism in the form of conditional scenarios. The visual syntax of TMSCs closely resembles that of MSCs; the semantics allows us to translate a TMSC specification into a framework that supports a notion of refinement based on Denicolas and Hennessys must preorder. A simple but non-trivial example illustrates the utility of our extension to MSCs.

TRIM: A Tool for Triggered Message Sequence Charts

TRIM is a tool for analyzing system requirements expressed using Triggered Message Sequence Charts (TMSCs). TMSCs enhance MSCs with capabilities for expressing conditional and partial behavior and with a refinement ordering. This paper shows how the Concurrency Workbench of the New Century may be adapted to check refinements between TMSC specifications.

An integrated framework for scenarios and state machines

This paper develops a semantic framework for interpreting heterogeneous system specifications consisting of a mixture of scenario-based requirements and state-based design. Such specifications arise naturally in spiral- and refinement-based development methodologies in which parts of a system have detailed designs while others exist in more abstract form as a collection of requirements. More precisely, we consider the scenario-based notation of Triggered Message Sequence Charts (TMSCs) and the state-based notation of Communicating State Machines (CSMs), and show how they may be integrated in a semantic framework that is founded on the mathematical theory of acceptance trees. Our semantic theory is also equipped with a robust notion of refinement, which allows us to relate one heterogeneous specification with another. A case-study serves to illustrate the utility of our framework as a basis for the principled evolution of higher-level requirements to lower-level operational specifications.

Secure requirements elicitation through triggered message sequence charts

This paper argues for performing information-flow-based securityanalysis in the first phase of the software development life cycle itself ie in the requirements elicitation phase Message Sequence Charts (MSC)s have been widely accepted as a formal scenario-based visual notation for writing down requirements In this paper, we discuss a method for checking if a TMSC (Triggered Message Sequence Chart), a recently propsed enhancement to classical MSCs, satisifes one of the most important information flow properties namely non-interference.

Executable requirements specifications using triggered message sequence charts

Triggered Message Sequence Charts (TMSCs) are a scenario-based visual formalism for early stage requirements specifications of distributed systems. In this paper, we present a formal operational semantics for TMSCs that allow the simulation of TMSC system descriptions, so that errors and inconsistencies in specification may be detected early on. The semantics is defined in terms of Structured Operational Semantics (SOS) rules that guide the step-wise execution of TMSC specifications. We also consider the equivalence of this semantics and the TMSC denotational semantics that has been presented in previous work.