Stephen S. Yau

Reconfigurable context-sensitive middleware for pervasive computing

Context-sensitive applications need data from sensors, devices, and user actions, and might need ad hoc communication support to dynamically discover new devices and engage in spontaneous information exchange. Reconfigurable Context-Sensitive Middleware facilitates the development and runtime operations of context-sensitive pervasive computing software.

Some Stability Measures for Software Maintenance

Software maintenance is the dominant factor contributing to the high cost of software. In this paper, the software maintenance process and the important software quality attributes that affect the maintenance effort are discussed. One of the most important quality attributes of software maintainability is the stability of a program, which indicates the resistance to the potential ripple effect that the program would have when it is modified. Measures for estimating the stability of a program and the modules of which the program is composed are presented, and an algorithm for computing these stability measures is given. An algorithm for normalizing these measures is also given. Applications of these measures during the maintenance phase are discussed along with an example. An indirect validation of these stability measures is also given. Future research efforts involving application of these measures during the design phase, program restructuring based on these measures, and the development of an overall maintainability measure are also discussed.

Dynamic audit services for integrity verification of outsourced storages in clouds

In this paper, we propose a dynamic audit service for verifying the integrity of an untrusted and outsourced storage. Our audit service is constructed based on the techniques, fragment structure, random sampling and index-hash table, supporting provable updates to outsourced data, and timely abnormal detection. In addition, we propose a probabilistic query and periodic verification for improving the performance of audit services. Our experimental results not only validate the effectiveness of our approaches, but also show our audit system verifies the integrity with lower computation overhead, requiring less extra storage for audit metadata.

Ripple effect analysis of software maintenance

Maintenance of large-scale software systems is a complex and expensive process. Large-scale software systems often possess both a set of functional and performance requirements. Thus, it is important for maintenance personnel to consider the ramifications of a proposed program modification from both a functional and a performance perspective. In this paper the ripple effect which results as a consequence of program modification will be analyzed. A technique is developed to analyze this ripple effect from both functional and performance perspectives. A figure-of-merit is then proposed to estimate the complexity of program modification. This figure can be used as a basis upon which various modifications can be evaluated.

Dynamic Audit Services for Outsourced Storages in Clouds

In this paper, we propose a dynamic audit service for verifying the integrity of an untrusted and outsourced storage. Our audit service is constructed based on the techniques, fragment structure, random sampling, and index-hash table, supporting provable updates to outsourced data and timely anomaly detection. In addition, we propose a method based on probabilistic query and periodic verification for improving the performance of audit services. Our experimental results not only validate the effectiveness of our approaches, but also show our audit system verifies the integrity with lower computation overhead and requiring less extra storage for audit metadata.

Design Stability Measures for Software Maintenance

The high cost of software during its life cycle can be attributer largely to software maintenance activities, and a major portion of these activities is to deal with the modifications of the software. In this paper, design stability measures which indicate the potential ripple effect characteristics due to modifications of the program at the design level are presented. These measures can be generated at any point in the design phase of the software life cycle which enables early maintainability feedback to the software developers. The validation of these measures and future research efforts involving the development of a user-oriented maintainability measure, which incorporates the design stability measures as well as other design measures, are discussed.

An Approach to Concurrent Control Flow Checking

A control flow checking scheme capable of detecting control flow errors of programs resulting from software coding errors, hardware malfunctions, or memory mutilation during the execution of the program is presented. In this approach, the program is partitioned into loop-free intervals and a database containing the path information in each of the loop-free intervals is derived from the detailed design. The path in each loop-free interval actually traversed at run time is recorded and then checked against the information provided in the database, and any discrepancy indicates an error. This approach is general, and can detect all uncompensated illegal branches. Any uncompensated error that occurs during the execution of a loop-free interval and manifests itself as a wrong branch within the loop-free interval or right after the completion of execution of the loop-free interval is also detectable. The approach can also be used to check the control flow in the testing phase of program development. The capabilities, limitations, implementation, and the overhead of using this approach are discussed.

Associative Processor Architecture—a Survey

A survey of the architecture of various associative processors is presented with emphasis on their characteristics, categorization, and implementation, and especially on recent developments. Based on their architecture, associative processors are classified into four categories, namely fully parallel, bit-serial, word-serial and block-oriented. The fully parallel associative processors are divided into two classes, word-orgamzed and distributed logic associative processors.

Hierarchical situation modeling and reasoning for pervasive computing

Situation awareness is one of the most fundamental features of entities in pervasive computing environments to dynamically adapt their behavior to situation changes to satisfy user requirements, including security and privacy. In order to support situation-aware adaptation, it is necessary to model and specify context and situation in a way such that multiple entities can easily exchange, share and reuse their knowledge on context and situation. In this paper, an OWL-based situation ontology to model situation hierarchically to facilitate sharing and reusing of situation knowledge and logic inferences is presented. The conversion of OWL situation ontology specifications to the first-order logic (FOL) representations, and the performance of FOL rule-based reasoning in terms of problem size and time are discussed

Universal Logic Modules and Their Applications

Recent advances in integrated circuit technology and its potential advantage in logical design have motivated the search for modular synthesis techniques for logic networks. This problem may be divided into two parts: find appropriate modules; and develop efficient synthesis techniques for logic networks using a minimum number of modules. In this paper a new type of universal logic modules (ULMs) called the Q-type is presented. The Q-type ULMs are superior to the existing ULMs in the sense that they require fewer input/output terminals when n≥6 where n is the number of input variables of the ULM. Various techniques for synthesizing a logic network with a small number of ULMs are discussed. A much simpler type of modules, which is suitable to realize any symmetric or partially symmetric function and can be used as auxiliary building blocks for realizing any given logic function, is presented. A special kind of ULMs, called serially controlled ULMs which has only n+ 3 input/ output terminals, is also presented. For a ULM of this kind the signals for specifying the logic function to be realized are serially applied to one of its input terminals.