39997807
Component-Based Software Engineering
We discuss some of the difficulties and significant issues that we need to consider when developing a formal method for component-based software engineering. We argue that to deal with the challenges, there is a need in research to link existing theories and methods of programming for effective support to component-based software engineering. We then present our initiative on a unified multi-view approach to modelling, design and analysis of component systems, emphasising the integration of models for different views.
14189544
Verification, refinement and scheduling of real-time programs
Abstract A real-time program can be developed by refining a specification into program code. Verification of the timing properties of the program is then usually done at two levels: verification of the ordering of timed actions in the program and proof that execution of the program on a specific system will meet its timing requirements. Refinement is done within a formal model but the second step requires a different framework in which scheduling theory analysis is used and actual program execution times can be taken into account. The implementation of a program on a system is said to be feasible or schedulable if it will meet all the timing deadlines. This paper shows how the feasibility of scheduling a real-time program can also be proved as a step in the refinement of the program from its specification. Verification of this step of refinement makes use of methods from scheduling theory within a formal system development framework.
7323063
rCOS: Refinement of Component and Object Systems
We present a model of object-oriented and component-based refinement. For object-orientation, the model is class-based and refinement is about correct changes in the structure, methods of classes and the main program, rather than changes in the behaviour of individual objects. This allows us to prove refinement laws for both high level design patterns and low level refactoring. For component-based development, we focus on the separation of concerns of interface and functional contracts, leaving refinement of interaction protocols in future work. The model supports the specification of these aspects at different levels of abstractions and their consistency. 
 
Based on the semantics, we also provide a general definitional approach to defining different relational semantic models with different features and constraints.
216012840
Specification and verification of fault-tolerance, timing, and scheduling
Fault-tolerance and timing have often been considered to be implementation issues of a program, quite distinct from the functional safety and liveness properties. Recent work has shown how these no...
16560725
rCOS: A refinement calculus of object systems
This article presents a mathematical characterization of object-oriented concepts by defining an observation-oriented semantics for a relational object-based language with a rich variety of features including subtypes, visibility, inheritance, type casting, dynamic binding and polymorphism. The language can be used to specify object-oriented designs as well as programs. We present a calculus that supports both structural and behavioural refinement of object-oriented designs. The design calculus is based on the predicate logic in Hoare and He's Unifying Theories of Programming (UTP).
13004956
Consistency checking of UML requirements
This paper discusses how to check consistency of UML requirements model which consists of a use case model and a conceptual class model with system constraints. Based on a given semantics, the requirements consistency can be defined and checked formally. The consistency among use cases and constraints are classified into five types. A system operation of interaction between actor and system is formally defined as a pair of pre and post conditions. An atomic use case is described as one system operation, and a composed use case may be defined as several system operations described by an activity diagram. Thus, each use case can also be modelled as a pair of pre and post conditions by composing the pre and post conditions of system operations by introducing a sequence composition operation. Requirement consistency can be logically checked based on the semantics. A simple library system is used as a case study to illustrate the feasibility of the method.
207320245
Hidden Markov models with factored Gaussian mixtures densities
We present a factorial representation of Gaussian mixture models for observation densities in hidden Markov models (HMMs), which uses the factorial learning in the HMM framework. We derive the reestimation formulas for estimating the factorized parameters by the Expectation Maximization (EM) algorithm and propose a novel method for initializing them. To compare the performances of the proposed models with that of the factorial hidden Markov models and HMMs, we have carried out extensive experiments which show that this modelling approach is effective and robust.
16029762
Preemptive Scheduling with Variable Profile, Precedence Constraints and Due Dates
Abstract This paper is concerned with the problem of scheduling preemptive tasks subject to precedence constraints in order to minimize the maximum lateness and the makespan. The number of available parallel processors is allowed to vary in time. It is shown that when an earliest due date first algorithm provides an optimal nonpreemptive schedule for unit-execution-time (UET) tasks, the preemptive priority scheduling algorithm, referred to as smallest laxity first, provides an optimal preemptive schedule for real-execution-time (RET) tasks. When the objective is to minimize the makespan, we get the same kind of result between highest level first schedules solving nonpreemptive tasks with UET and the longest remaining path first schedule for the corresponding preemptive scheduling problem with RET tasks. These results are applied to four specific profile scheduling problems and new optimality results are obtained.
28594120
Pattern recognition using Markov random field models
In this paper, we propose Markov random field models for pattern recognition, which provide a flexible and natural framework for modelling the interactions between spatially related random variables in their neighbourhood systems. The proposed approach is superior to conventional approaches in many aspects. This paper introduces the concept of states into Markov random filed models, presents a theoretic analysis of the approach, discusses issues of designing neighbourhood system and cliques, and analyses properties of the models. We have applied our method to the recognition of unconstrained handwritten numerals. The experimental results show that the proposed approach can achieve high performance.
8930290
Data mining of gene expression changes in Alzheimer brain
Genome-wide transcription profiling is a powerful technique for studying the enormous complexity of cellular states. Moreover, when applied to disease tissue it may reveal quantitative and qualitative alterations in gene expression that give information on the context or underlying basis for the disease and may provide a new diagnostic approach. However, the data obtained from high-density microarrays is highly complex and poses considerable challenges in data mining. The data requires care in both pre-processing and the application of data mining techniques. This paper addresses the problem of dealing with microarray data that come from two known classes (Alzheimer and normal). We have applied three separate techniques to discover genes associated with Alzheimer disease (AD). The 67 genes identified in this study included a total of 17 genes that are already known to be associated with Alzheimer's or other neurological diseases. This is higher than any of the previously published Alzheimer's studies. Twenty known genes, not previously associated with the disease, have been identified as well as 30 uncharacterized expressed sequence tags (ESTs). Given the success in identifying genes already associated with AD, we can have some confidence in the involvement of the latter genes and ESTs. From these studies we can attempt to define therapeutic strategies that would prevent the loss of specific components of neuronal function in susceptible patients or be in a position to stimulate the replacement of lost cellular function in damaged neurons. Although our study is based on a relatively small number of patients (four AD and five normal), we think our approach sets the stage for a major step in using gene expression data for disease modeling (i.e. classification and diagnosis). It can also contribute to the future of gene function identification, pathology, toxicogenomics, and pharmacogenomics.
15316832
Multimedia search and retrieval: new concepts, system implementation, and application
We first present new concepts applicable to the design of multimedia search and retrieval schemes in general, and to MPEG-7 in particular, the multimedia description standard in progress. Raw multimedia data is assumed to exist in the form of programs that typically consist of a combination of media types such as visual, audio, and text. We partition each such media stream into smaller units based on actual physical events. These physical events within each media stream can then be effectively indexed for retrieval. The concept of logical events is introduced next; we define logical events as those that can provide different "views" of the content as may be desired by a user. Such events usually result from either the correlation of events that cross different media types, of by merging recursively chosen events from a lower level within each media type. We then address the related issue of how to develop a practical multimedia information retrieval system that exploits the aforementioned concepts of physical and logical events as well as other aspects such as storage, representation and indexing to enable efficient search, retrieval, and browsing. Finally, we implement the proposed concepts and solutions within a multimedia system that addresses a real application, effective browsing of broadcast news, and evaluate its performance.