Viterbi training (VT) provides a fast but inconsistent estimator of hidden Markov models (HMM). The inconsistency is alleviated with a little extra computation when we enable VT to asymptotically fix the true values of the parameters. This relies on infinite Viterbi alignments and associated with them limiting probability distributions. First in a sequel, this article is a proof of concept; it focuses on mixture models, an important but special case of HMM where the limiting distributions can be calculated exactly. A simulated Gaussian mixture shows that our central algorithm (VA1) can significantly improve the accuracy of VT with little extra cost. Next in the sequel, we present elsewhere a theory of the adjusted VT for the general HMMs, where the limiting distributions are more challenging to find. Here, we also present another, more advanced correction to VT and verify its fast convergence and high accuracy; its computational feasibility requires additional investigation.

This article deals with the effect of information and uncertainty on profits in an unobservable single-server queuing system. We consider scenarios in which the service rate, the service quality, or the waiting conditions are random variables that are known to the server but not to the customers. We ask whether the server is motivated to reveal these parameters. We investigate the structure of the profit function and its sensitivity to the variance of the random variable. We consider and compare variations of the model according to whether the server can modify the service price after observing the realization of the random variable.

We study weighted path lengths (depths) and distances for increasing tree families. For those subclasses of increasing tree families, which can be constructed via an insertion process (e.g., recursive trees, plane-oriented recursive trees, and binary increasing trees), we can determine the limiting distribution that can be characterized as a generalized Dickman's infinitely divisible distribution.

We consider a markovian multiserver queue with a finite waiting line in which a customer may decide to leave and give up service if its waiting time in queue exceeds its random deadline. We focus on the performance measure in terms of the probability of being served under both transient and stationary regimes. We investigate monotonicity properties of first and second order of this performance with respect to the buffer size, say k. Under the stationary regime, we prove that our service level is strictly increasing and concave in k, whereas we prove under the transient regime that it is only increasing in k.

Engineering design reviews, which take place at predetermined phases of the product development process, are fundamental elements for the evaluation and control of engineering activities. These meetings are also acknowledged as unique opportunities for all the parties involved to share information about the product and related engineering processes. For product development teams, the knowledge generated during a design review is not as secondary as it may seem; key design decisions, design experiences, and associated rationale are frequently made explicit. Useful work has been carried out on the design review process itself, but little work has been undertaken about the detailed content of the meeting activity; it is argued that understanding the transactions that take place during a meeting is critical to building an effective knowledge-oriented recording strategy. To this effect, an extensive research program based on case studies in the aerospace engineering domain has been carried out. The work reported in this paper focuses on a set of tools and methods developed to characterize and analyze in depth the transactions observed during a number of case studies. The first methodology developed, the transcript coding scheme, uses an intelligent segmentation of meeting discourse transcriptions. The second approach, which bypasses the time consuming transcribing operation, is based on a meeting capture template developed to enable a meeting observer to record the transactions as the meeting takes place. A third method, the information mapping technique, has also been developed to interpret the case study data in terms of decisions, actions, rationale, and lessons learned, effectively generating qualitative measures of the information lost in the formal records of design reviews. Overall, the results generated by the set of tools presented in this paper have fostered a practical strategy for the knowledge intensive capture of the contents of design reviews. The concluding remarks also discuss possible enhancements to the meeting analysis tools presented in this paper and future work aimed at the development of a computer supported capture software for design reviews.

Successful realization of large-scale product development programs is challenging because of complex product and process dependencies and complicated team interactions. Proficient teamwork is underpinned by knowledge of the manner in which tasks performed by different design participants fit together to create an effective whole. Based on an extensive industrial case study with a diesel engine company, this paper first argues that the overview and experience of senior designers play an important part in supporting teamwork by coordinating activities and facilitating proactive communication across large project teams. As experts move on and novices or contractors are hired, problems are likely to occur as tacit overview knowledge is lost. If informal, overview-driven processes break down, the risk of costly oversights will increase, and greater management overhead will be required to realize successful product designs. Existing process models provide a means to express the connectivity between tasks and components thus to compensate partially for the loss of tacit overview. This paper proposes the use of design confidence, a metric that reflects the designer's belief in the maturity of a particular design parameter at a given point in the process, to address the limitations of existing models. The applicability of confidence-based design models in providing overview, as well as their shortcomings, will be demonstrated through the example of a diesel engine design process. Confidence can be used to make overview knowledge explicit and convey additional information about the design artifact, thereby informing communication and negotiation between teams.

Agent models provide a generalized approach to the design of systems that autonomously monitor and affect an environment. Societies of agents that reason and communicate about an environment can achieve complex emergent behavior to facilitate and augment human activities. This paper introduces artificial agent technologies as a means by which the behavioral complexity of virtual worlds can be extended to provide the functionality needed to support collaboration in multidisciplinary design teams. Three key roles are identified that artificial agents can play to provide this functionality: support for multiple views of designed objects, support for the expression of relationships between designed objects, and compatibility with existing design tools. The implementation of a society of agents fulfilling these roles within a virtual world based, multidisciplinary design tool called DesignWorld is described. The increased behavioral complexity and functionality of DesignWorld's underlying virtual world is demonstrated using the results of multidisciplinary design experiments with DesignWorld.

Readily available and affordable technologies such as the Internet, groupware, and Web conferencing mean that sharing information and data within teams is simple and affordable. However, many small- and medium-sized enterprises (SMEs) struggle to implement or perform distributed collaborative design effectively or even at all. As part of the extended design team of large multinational companies it is not uncommon for SMEs to have collaborative working tools and practice imposed on them to meet the requirements of the multinational. However, many SMEs need to develop their own working practices to support effective, collaborative team design within their own organization or their extended design team. Through a series of case studies, this paper describes how a typical SME achieved successful distributed team design within their organization. A “strategy for effective distributed team design” encompassing the processes, methods, and tools developed and implemented within the company to achieve this success, is presented. In total, four live case studies, spanning a 2-year period, are described; two initial studies focus on current distributed design team practice clearly highlighting issues and areas for improvement, leading to the development of processes, methods, and tools to support distributed collaborative team design. A strategy for effective distributed team design encapsulating these processes methods and tools is presented together with its evaluation through two further live industrial case studies. The case studies themselves, together with the processes, methods, and tools developed by this company, could be adopted by other SMEs directly to achieve the same success. Generic and transferable findings drawn from this study aimed at helping others achieve this success form the conclusion of the paper.

Architecture, engineering, and construction team members, while collaborating on building projects, rely on past experiences and content through the use of project design archives (whether in paper or digital format). Underutilization of potential knowledge in the decision-making process of data, information, and knowledge reuse is limited by access to these archives, because of sheer size, decontextualized content, and inconvenient access and presentation. This paper presents an integrated solution called CoMem–iRoom that leverages two technologies Corporate Memory (CoMem) and interactive Room (iRoom) developed at Stanford. CoMem–iRoom addresses critical limitations (content, context, visualization, and interactivity) constraining the process of collaborative exploration toward knowledge reuse and decision making.

It is generally known that architectural practice relies heavily on the interactions between architects and other professionals. However, during their formal education, most students attending architecture schools, and engineering schools for that matter, get very little (if any) exposure to decision making in conditions that involve expertise and/or worldviews beyond those reflected and valued by their own discipline. In the past 10 years, a project-based learning initiative was developed between the University of California, Berkeley, and Stanford University in an international context involving several other universities around the world. Throughout this experience, we have identified several issues that have shown to be crucial to these interactions. This paper elaborates on three key issues: improvement of communication skills, empowerment through developing strategies of leadership, and recognition of own and others' worldviews. We also make the case to include experiential educational situations that can introduce these aspects into the academic curricula of architecture and engineering schools.

This paper presents an ontological framework for situated design teams in which the team is both the subject and the object of designing. Team designing is modeled using the set of processes provided by the situated function–behavior–structure framework. This is a formal basis for understanding the drivers for change in the product to be designed and in the design team. We specifically focus on changes in a team's structure that emerge from interactions among individual team members and subteams.

This paper introduces projective systems for topological and probabilistic event structures. The projective formalism is used for studying the domain of configurations of a prime event structure and its space of maximal elements. This is done from both a topological and a probabilistic viewpoint. We give probability measure extension theorems in this framework.

This second special issue devoted to ‘developments in computational models’ (the first was Volume 16 Issue 4) came out of an open call for papers following the First International Workshop on Developments in Computational Models (DCM). This took place in Lisbon, Portugal, on the 10th July 2005, and was a satellite event of ICALP 2005 focused on abstract models of computation and their associated programming paradigms.

A restriction category is an abstract formulation for a category of partial maps, defined in terms of certain specified idempotents called the restriction idempotents. All categories of partial maps are restriction categories; conversely, a restriction category is a category of partial maps if and only if the restriction idempotents split. Restriction categories facilitate reasoning about partial maps as they have a purely algebraic formulation.

In this paper we consider colimits and limits in restriction categories. As the notion of restriction category is not self-dual, we should not expect colimits and limits in restriction categories to behave in the same manner. The notion of colimit in the restriction context is quite straightforward, but limits are more delicate. The suitable notion of limit turns out to be a kind of lax limit, satisfying certain extra properties.

Of particular interest is the behaviour of the coproduct, both by itself and with respect to partial products. We explore various conditions under which the coproducts are ‘extensive’ in the sense that the total category (of the related partial map category) becomes an extensive category. When partial limits are present, they become ordinary limits in the total category. Thus, when the coproducts are extensive we obtain as the total category a lextensive category. This provides, in particular, a description of the extensive completion of a distributive category.

We present a simple module calculus where selection and execution of a component is possible on open modules, that is, modules that still need to import some external definitions. Hence, it provides a kernel model for a computational paradigm in which standard execution (that is, execution of a single computation described by a fragment of code) can be interleaved with operations at the meta-level, which can manipulate in various ways the context in which this computation takes place. Formally, this is achieved by introducing configurations as basic terms. These are, roughly speaking, pairs consisting of an (open, mutually recursive) collection of named components and a term representing a program running in the context of these components. Configurations can be manipulated by classical module/fragment operators, hence reduction steps can be either execution steps of the program or steps that perform module operations (called reconfiguration steps).

Since configurations combine the features of lambda abstractions (first-class functions), records, environments with mutually recursive definitions and modules, the calculus extends and integrates both traditional module calculi and recursive lambda calculi. We state confluence of the calculus, and propose different ways to prevent errors arising from the lack of some required component, either by a purely static type system or by a combination of static and run-time checks. Moreover, we define a call-by-need strategy that performs module simplification only when needed and only once, leading to a generalisation of call-by-need lambda calculi that includes module features. We prove the soundness and completeness of this strategy using an approach based on information content, which also allows us to preserve confluence, even when local substitution rules are added to the calculus.

In this paper we discuss the following interesting question about accepting hybrid networks of evolutionary processors (AHNEP), which are a recently introduced bio-inspired computing model. The question is: how many processors are required in such a network to recognise a given language L? Two answers are proposed for the most general case, when L is a recursively enumerable language, and both answers improve on the previously known bounds. In the first case the network has a number of processors that is linearly bounded by the cardinality of the tape alphabet of a Turing machine recognising the given language L. In the second case we show that an AHNEP with a fixed underlying structure can accept any recursively enumerable language. The second construction has another useful property from a practical point of view as it includes a universal AHNEP as a subnetwork, and hence only a limited number of its parameters depend on the given language.

We extend the coalgebraic account of specification and refinement of objects and classes in object-oriented programming given by Reichel and Jacobs to (generalised) binary methods. These are methods that take more than one parameter of a class type. Class types include products, sums and powerset type constructors. To allow for class constructors, we model classes as bialgebras. We study and compare two solutions for modelling generalised binary methods, which use purely covariant functors.

In the first solution, which applies when we already have a class implementation, we reduce the behaviour of a generalised binary method to that of a bunch of unary methods. These are obtained by freezing the types of the extra class parameters to constant types. If all parameter types are finitary, the bisimilarity equivalence induced on objects by this model yields the greatest congruence with respect to method application.

In the second solution, we treat binary methods as graphs instead of functions, thus turning contravariant occurrences in the functor into covariant ones.

We show the existence of final coalgebras in both cases.

We define BACI(Boxed Ambients with Communication Interfaces), an ambientcalculus with a flexible communication policy. Traditionally, typed ambientcalculi have a fixed communication policy determining the kind of informationthat can be exchanged with a parent ambient, even though mobility changes theparent. BACI lifts that restriction, allowing differentcommunication policies with different parents during computation. Furthermore,BACI separates communication and mobility by making thechannels of communication between ambients explicit. In contrast with othertyped ambient calculi where communication policies are global, each ambient inBACI is equipped with a description of the communicationpolicies ruling its information exchange with parent and child ambients. Thecommunication policies of ambients increase when they move: more precisely, whenan ambient enters another ambient, the entering ambient and the host ambient canexchange their communication ports and agree on the kind of information to beexchanged. This information is recorded locally in both ambients.

We show the type-soundness of BACI, proving that it satisfies thesubject reduction property, and we study its behavioural semantics by means of alabelled transition system.