William G. Wood

Scaling up software architecture analysis

This paper will show how architecture design and analysis techniques rest on a small number of foundational principles. We will show how those principles have been instantiated as a core set of techniques. These techniques, combined together, have resulted in several highly successful architecture analysis and design methods. Finally, we will show how these foundations, and the techniques that instantiate them, can be re-combined for new purposes addressing problems of ever-increasing scale, specifically: addressing the highly complex problems of analyzing software-intensive ecosystems.

Temporal logic case study

This report is a case study applying temporal logic to specify the operation of a bank of identical elevators servicing a number of floors in a building. The goal of the study was to understand the application of temporal logic in a problem domain that is appropriate for the method, and to determine some of the strengths and weaknesses of temporal logic in this domain. The case study uses a finite state machine language to build a model of the system specification, and verifies that the temporal logic specifications are consistent using this model. The specification aspires to be complete, consistent, and unambiguous.

Assessing the Quality of Large, Software-Intensive Systems: A Case Study

This paper presents a case study in carrying out an audit of a large, softwareintensive system. We discuss our experience in structuring the team for obtaining maximum effectiveness under a short deadline. We also discuss the goals of an audit, the methods of gathering and assimilating information, and specific lines of inquiry to be followed. We present observations on our approach in light of our experience and feedback from the customer. In the past decade, as engineers have attempted to build software-intensive systems of a scale not dreamed of heretofore, there have been extraordinary successes and failures. Those projects that have failed have often been spectacular and highly visible [3], particularly those commissioned with public money. Such failures do not happen all at once; like Brooks’ admonition that schedules slip one day at a time [2], failures happen incrementally. The symptoms of a failing project range from the subtle (a customer’s vague feelings of uneasiness) to the ridiculous (the vendor slips the schedule for the eighth time and promises that another

A Specification of the Cat and Mouse Problem

30 million will fix everything). A project that has passed the “failure in progress” stage and gone on to full-fledged meltdown can be spotted by one sure symptom: the funding authority curtails payment and severely slows development. When that happens, the obvious question is asked by every involved party: “What now?” The answer is often an audit. This paper summarizes the experience of an audit undertaken by the Software Engineering Institute (SEI) in the summer of 1994 to examine a large, highly visible development effort exhibiting the meltdown symptom suggested above. The customer was a government agency in the process of procuring a large software-intensive system from a major contractor. The audit team included the authors of this paper, as well as members from other organizations. Members of the team had extensive backgrounds and expertise in software engineering, in large systems development,

Government product lines

The cat and mouse problem described herein was proposed as a sample real-time pedagogical problem at the REX workshop. It is very simple, and includes some real-time aspects. I decided to specify this particular problem to demonstrate one way of dealing with time in the specification language Z. This paper contains a description of the problem, the Z specification, and a justification for choosing Z as the specification language.

Application of formal methods to system and software specification

Government agencies often acquire large-scale software-intensive systems to be installed in many sites widely distributed across the country. These are often single-baseline systems that must be tailored to the particular environment of a site to allow for variations in both physical and functional configurations. Such systems often take a long time to develop and distribute to the sites; by the time the installations are completed, the system components are close to, or past obsolescence since technology is continuously evolving. This inevitably leads to a future “big bang” acquisition. This paper proposes that these problems can be resolved by considering the systems to be a product line that evolves incrementally, with new technology and functionality added over the lifetime of the product line. In this way the systems will remain state-of-the-shelf and avoid a future “big bang” acquisition.

Quality Attribute Workshops (QAWs), Third Edition

This position paper describes our efforts to apply formal, methods to the specification of complex systems and the overlap of these efforts with the topics of the workshop. The introduction describes why we are interested in using formal methods, and it is followed by short descriptions of the individual tasks with which we are currently involved. The conclusion relates these tasks to the workshop topics.