Aspect] is a simple and practical aspect-oriented extension to Java With just a few new constructs, AspectJ provides support for modular implementation of a range of crosscutting concerns. In AspectJ's dynamic join point model, join points are well-defined points in the execution of the program; pointcuts are collections of join points; advice are special method-like constructs that can be attached to pointcuts; and aspects are modular units of crosscutting implementation, comprising pointcuts, advice, and ordinary Java member declarations. AspectJ code is compiled into standard Java bytecode. Simple extensions to existing Java development environments make it possible to browse the crosscutting structure of aspects in the same kind of way as one browses the inheritance structure of classes. Several examples show that AspectJ is powerful, and that programs written using it are easy to understand.

An overview of AspectJ

In this paper, we review current requirements engineering (RE) research and identify future research directions suggested by emerging software needs. First, we overview the state of the art in RE research. The research is considered with respect to technologies developed to address specific requirements tasks, such as elicitation, modeling, and analysis. Such a review enables us to identify mature areas of research, as well as areas that warrant further investigation. Next, we review several strategies for performing and extending RE research results, to help delineate the scope of future research directions. Finally, we highlight what we consider to be the "hot" current and future research topics, which aim to address RE needs for emerging systems of the future.

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Research Directions in Requirements Engineering

Inevitably, reading is one of the requirements to be undergone. To improve the performance and quality, someone needs to have something new every day. It will suggest you to have more inspirations, then. However, the needs of inspirations will make you searching for some sources. Even from the other people experience, internet, and many books. Books and internet are the recommended media to help you improving your quality and performance.

Feature-Oriented Software Product Lines

Automated program repair recently received considerable attentions, and many techniques on this research area have been proposed. Among them, two genetic-programming-based techniques, GenProg and Par, have shown the promising results. In particular, GenProg has been used as the baseline technique to check the repair effectiveness of new techniques in much literature. Although GenProg and Par have shown their strong ability of fixing real-life bugs in nontrivial programs, to what extent GenProg and Par can benefit from genetic programming, used by them to guide the patch search process, is still unknown. To address the question, we present a new automated repair technique using random search, which is commonly considered much simpler than genetic programming, and implement a prototype tool called RSRepair. Experiment on 7 programs with 24 versions shipping with real-life bugs suggests that RSRepair, in most cases (23/24), outperforms GenProg in terms of both repair effectiveness (requiring fewer patch trials) and efficiency (requiring fewer test case executions), justifying the stronger strength of random search over genetic programming. According to experimental results, we suggest that every proposed technique using optimization algorithm should check its effectiveness by comparing it with random search.

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The strength of random search on automated program repair

Automated program repair has shown promise for reducing the significant manual effort debugging requires. This paper addresses a deficit of earlier evaluations of automated repair techniques caused by repairing programs and evaluating generated patches' correctness using the same set of tests. Since tests are an imperfect metric of program correctness, evaluations of this type do not discriminate between correct patches and patches that overfit the available tests and break untested but desired functionality. This paper evaluates two well-studied repair tools, GenProg and TrpAutoRepair, on a publicly available benchmark of bugs, each with a human-written patch. By evaluating patches using tests independent from those used during repair, we find that the tools are unlikely to improve the proportion of independent tests passed, and that the quality of the patches is proportional to the coverage of the test suite used during repair. For programs that pass most tests, the tools are as likely to break tests as to fix them. However, novice developers also overfit, and automated repair performs no worse than these developers. In addition to overfitting, we measure the effects of test suite coverage, test suite provenance, and starting program quality, as well as the difference in quality between novice-developer-written and tool-generated patches when quality is assessed with a test suite independent from the one used for patch generation.

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Is the cure worse than the disease? overfitting in automated program repair

Middleware technologies such as Web Services, CORBA and DCOM have been very successful in solving distributed computing problems for a large family of application domains. As middleware systems are getting widely adopted and more functionally mature, it is also increasingly difficult for the architecture of middleware to achieve a high level of adaptability and configurability, due to the limitations of traditional software decomposition methods. Aspect oriented programming has brought us new design perspectives because it permits the superimpositions of multiple abstraction models on top of one another. It is a very powerful technique in separating and simplifying design concerns. In this paper, we first show that, through the quantification of aspects in the legacy implementations, the modularity of middleware architecture is greatly hindered by the ubiquitous existence of tangled logic. We then go one step further by factoring out a number of aspects identified in the mining work and re-implementing them as aspect programs. The aspect oriented re-factorization allows us to apply a set of software engineering metrics to quantify the changes of the re-factored system in both the structural complexity and the runtime performance. The aspect oriented re-factoring proves that the aspect oriented programming is capable of composing orthogonal design requirements. The final "woven" system is able to correctly provide both the fundamental functionality and the "aspectized" functionality with negligible overhead and a leaner architecture. Further more, the configurability of middleware is dramatically increased because the "aspectized" features can be configured in and out during the compile-time

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Quantifying aspects in middleware platforms

We present CLAP, a new technique to reproduce concurrency bugs. CLAP has two key steps. First, it logs thread local execution paths at runtime. Second, offline, it computes memory dependencies that accord with the logged execution and are able to reproduce the observed bug. The second step works by combining constraints from the thread paths and constraints based on a memory model, and computing an execution with a constraint solver.CLAP has four major advantages. First, logging purely local execution of each thread is substantially cheaper than logging memory interactions, which enables CLAP to be efficient compared to previous approaches. Second, our logging does not require any synchronization and hence with no added memory barriers or fences; this minimizes perturbation and missed bugs due to extra synchronizations foreclosing certain racy behaviors. Third, since it uses no synchronization, we extend CLAP to work on a range of relaxed memory models, such as TSO and PSO, in addition to sequential consistency. Fourth, CLAP can compute a much simpler execution than the original one, that reveals the bug with minimal thread context switches. To mitigate the scalability issues, we also present an approach to parallelize constraint solving, which theoretically scales our technique to programs with arbitrary execution length.Experimental results on a variety of multithreaded benchmarks and real world concurrent applications validate these advantages by showing that our technique is effective in reproducing concurrency bugs even under relaxed memory models; furthermore, it is significantly more efficient than a state-of-the-art technique that records shared memory dependencies, reducing execution time overhead by 45% and log size by 88% on average.

CLAP: recording local executions to reproduce concurrency failures

Middleware provides simplicity and uniformity for the development of distributed applications. However, the modularity of the architecture of middleware is starting to disintegrate and to become complicated due to the interaction of too many orthogonal concerns imposed from a wide range of application requirements. This is not due to bad design but rather due to the limitations of the conventional architectural decomposition methodologies. We introduce the principles of horizontal decomposition (HD) which addresses this problem with a mixed-paradigm middleware architecture. HD provides guidance for the use of conventional decomposition methods to implement the core functionalities of middleware and the use of aspect orientation to address its orthogonal properties. Our evaluation of the horizontal decomposition principles focuses on refactoring major middleware functionalities into aspects in order to modularize and isolate them from the core architecture. New versions of the middleware platform can be created through combining the core and the flexible selection of middleware aspects such as IDL data types, the oneway invocation style, the dynamic messaging style, and additional character encoding schemes. As a result, the primary functionality of the middleware is supported with a much simpler architecture and enhanced performance. Moreover, customization and configuration of the middleware for a wide-range of requirements becomes possible.

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Resolving feature convolution in middleware systems

With the proliferation of Web services, service engineers demand good automatic service composition algorithms that not only synthesize the correct work plans from thousands of services but also satisfy the quality requirements of the users. Our observation is that conventional approaches suffer from serious limitations in scalability and accuracy when addressing both requirements simultaneously. We have designed and implemented a tool QSynth to use QoS objectives of service requests as the search directives. This approach effectively prunes the search space and significantly improves the accuracy of the search results. Evaluations show that, compared to the state of the art, QSynth achieves superior scalability and accuracy with respect to a large variety of composition scenarios. Our design of QSynth won the performance championship of Web Services Challenge 2009.

QSynth: A Tool for QoS-aware Automatic Service Composition

The technique of deterministic record and replay aims at faithfully reenacting an earlier program execution. For concurrent programs, it is one of the most important techniques for program understanding and debugging. The state of the art deterministic replay techniques face challenging efficiency problems in supporting multi-processor executions due to the unoptimized treatment of shared memory accesses. We propose LEAP: a deterministic record and replay technique that uses a new type of local order w.r.t. the shared memory locations and concurrent threads. Compared to the related work, our technique records much less information without losing the replay determinism. The correctness of our technique is underpinned by formal models and a replay theorem that we have developed in this work. Through our evaluation using both benchmarks and real world applications, we show that LEAP is more than 10x faster than conventional global-order based approaches and, in most cases, 2x to 10x faster than other local-order based approaches. Our recording overhead on the two large open source multi-threaded applications Tomcat and Derby is less than 10%. Moreover, as the evidence of the deterministic replay, LEAP is able to deterministically reproduce 7 out of 8 real bugs in Tomcat and Derby, 13 out of 16 benchmark bugs in IBM ConTest benchmark suite, and 100% of the randomly injected concurrency bugs.

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Charles Zhang

Papers

Quantifying aspects in middleware platforms

CLAP: recording local executions to reproduce concurrency failures

Resolving feature convolution in middleware systems

QSynth: A Tool for QoS-aware Automatic Service Composition

LEAP: lightweight deterministic multi-processor replay of concurrent java programs