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.
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).
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.
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.
1176633
Consistent code generation from UML models
Relational calculus of object systems (rCOS) is an OO-language which is equipped with an observation-oriented semantics and a refinement calculus based on the Hoare and He's unifying theories of programming (UTP). In this paper, we give syntactic definitions for class diagrams and sequence diagrams in UML 2.0. Based on these definitions, we give an algorithm for checking the consistency of a class diagram and a sequence diagram. Furthermore, we develop an algorithm to generate rCOS code from any given consistent class diagram and sequence diagram.
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...
15783652
Low bit-rate video streaming for face-to-face teleconference
Face-to-face video teleconferencing is very important for real time communication. Current teleconferencing applications use standard video codecs, such as MPEG 1/2/4, for the compression of face video. Either a high bandwidth is required for high quality video transmission, or the transmitted face video is blurred at low bitrates. We present a system for real-time coding of face video at low bit-rate. There are two main contributions. First, we improve the technique of long term memory prediction by selecting frames into the database in an optimal way. A new frame is selected into the database only when it is significantly different from those frames which are already in the database. In this way, the database can cover a wider range of images. Second, we incorporate prior knowledge about faces into the long term memory prediction framework. The prior knowledge includes: (1) facial motions are repetitive such that most of them can be reconstructed from multiple reference frames; (2) different components of the face and the background can tolerate different levels of error because of different perceptual importance. Experiments show that, at similar PSNR, the proposed system works much faster and achieves better visual quality than the standard H.264/JVT codec.
3399031
On 2-factors in claw-free graphs
Abstract A graph is said claw-free if it contains no induced subgraph isomorphic to K 1,3 . We prove that if G is a claw-free graph with minimum degree δ ⩾4, then G contains a 2-factor with at most 6 n /( δ +2)−1 components. Moreover, together with a theorem of Choudoum and Paulraj (J. Graph Theory 15 (1991) 259–265) and one of Anstee (J. Algorithms 6 (1985) 112–131), it is polynomial (in O( n 3 )) to construct such a 2-factor.
242170
Active security support for active networks
Active networks aim to provide a software framework that enables network applications to customize the processing of their communication packets. Security is of critical importance to the success of active networking. This paper presents a design and a description of the implementation for securing the node of an active network using active networking principles. The secure node architecture includes an active node operating system security API, an active security guardian, and quality of protection (QoP) provisions. The architecture supports highly customized and situational policies created by users and applications dynamically. It permits active nodes to satisfy the application-specific dynamic security and protection requirements. The secure node architecture can provide a fundamental base for securing the active network infrastructure. We describe the integration of secure node architecture into an active network software system to demonstrate its flexible and innovative features.
118203
Concealed weapon detection and visualization in a synthesized image
Images acquired by heterogeneous image sensors may provide complementary information about the scene, for instance, the visual image can provide personal identification information like the facial pattern while the infrared (IR) or millimeter wave image can detect the suspicious regions of concealed weapons. Usually, a technique, namely multiresolution pixel-level image fusion is applied to integrate the information from multi-sensor images. However, when the images are significantly different, the performance of the multiresolution fusion algorithms is not always satisfactory. In this study, a new strategy consisting of two steps is proposed. The first step is to use an unsupervised fuzzy k-means clustering to detect the concealed weapon from the IR image. The detected region is embedded in the visual image in the second step and this process is implemented with a multiresolution mosaic technique. Therefore, the synthesized image retains the quality comparable to the visual image while the region of the concealed weapon is highlighted and enhanced. The experimental results indicate the efficiency of the proposed approach.
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.