We present a novel approach to optimization-based variation-tolerant analog circuit sizing. Using formal methods based on affine arithmetic, we calculate guaranteed bounds on the worst-case behavior and deterministically find the global optimum of the sizing problem by means of branch-and-bound optimization. To solve the nonlinear circuit equations with parameter variations, we define a novel affine-arithmetic Newton operator that gives a significant improvement in computational efficiency over an implementation using interval arithmetic. The calculation of guaranteed worst-case bounds and the global optimization are demonstrated by a prototype implementation.

We are developing a conceptual framework and a demonstration system for collaboration among members of design teams when direct communication among these members is impossible or impractical. Our research focuses on the long-term, indirect communication needs of project teams rather than the short-term needs of face-to-face communication or electronic mail. We address these needs with integrated, domain-oriented design environments. Our conceptual framework and our system-building efforts address two major issues: (a) How does individual work blend into project work (especially in large projects that span great distances and time)? and (b) What role do the work objects play in this coordination? We use a specific domain-oriented design environment (NETWORK-HYDRA—for the design of computer networks) to illustrate our approach, and we discuss HYDRA as the underlying domain-independent, multifaceted architecture for design environments.

Cooperativeproblem-solving systems help users design solutions themselves as opposed to having solutions designed for them, Critiquing-presenting a reasoned opinion about a user's product or action-is a major activity of a cooperative problem-solving system.Critics make the constructed artifact "talk back" to the user.Conditions under which critics are more appropriate than autonomous expert systems are discussed.Critics should be embedded in integrated design environments along with other components, such as an argumentative hypertext system, a specification component, and a catalog.Critics support learning as a by-product of problem solving.The major subprocesses of critiquing are goal acquisition, product analysis, critiquing strategies, adaptation capability, explanation and argumentation, and advisory capability.The generality of the critiquing approach is demonstrated by discussing critiquing systems developed in our group and elsewhere.Limitations of many current critics include their inability to learn about specific user goals and their intervention strategies.

We describe the critiquing approach to building knowledge-based interactive systems. Critiquing supports computer users in their problem solving and learning activities. The challenges for the next generation of knowledge-based systems provide a context for the development of this paradigm. We discuss critics from the perspective of overcoming the problems of high-functionality computer systems, of providing a new class of systems to support learning, of extending applications-oriented construction kits to design environments, and of providing an alternative to traditional autonomous expert systems. One of the critiquing systems we have built — JANUS, a critic for architectural design — is used as an example of the key aspects of the critiquing process. We also survey additional critiquing systems developed in our and other research groups.

Our goal is to build cooperative computer systems to augment human intelligence. In these systems, the communication between the user and the computer plays a crucial role. To provide the user with the appropriate level of control and a better understanding, we have to replace human-computer communication with human problem-domain communication, which allows users to concentrate on the problems of their domain and to ignore the fact that they are using a computer tool. Construction kits and design environments are tools that represent steps toward human problem-domain communication. A construction kit is a set of building blocks that models a problem domain. The building blocks define a design space (the set of all possible designs that can be created by combining these blocks). Design environments go beyond construction kits in that they bring to bear general knowledge about design (e.g., which meaningful artifacts can be constructed, how and which blocks can be combined with each other) that is useful for the designer. Prototypical examples of these systems (especially in the area of user interface design) are described in detail, and the feasibility of this approach is evaluated.