Shengru Tu

An application of Petri net reduction for Ada tasking deadlock analysis

As part of our continuing research on using Petri nets to support automated analysis of Ada tasking behavior, we have investigated the application of Petri net reduction for deadlock analysis. Although reachability analysis is an important method to detect deadlocks, it is in general inefficient or even intractable. Net reduction can aid the analysis by reducing the size of the net while preserving relevant properties. We introduce a number of reduction rules and show how they can be applied to Ada nets, which are automatically generated Petri net models of Ada tasking. We define a reduction process and a method by which a useful description of a detected deadlock state can be obtained from the reduced nets information. A reduction tool and experimental results from applying the reduction process are discussed.

Design and implementation of a Petri net based toolkit for Ada tasking analysis

The use of Petri nets for defining a general static analysis framework for Ada tasking is advocated. The framework has evolved into a collection of tools that have proven to be a very valuable platform for experimental research. The design and implementation of tools that make up the tasking-oriented toolkit for the Ada language (TOTAL) are defined and discussed. Modeling and query/analysis methods and tools are discussed. Example Ada tasking programs are used to demonstrate the utility of each tool individually as well as the way the tools integrate. TOTAL is divided into two major subsystems, the front-end translator subsystem (FETS) and the back-end information display subsystem (BIDS). Three component tools that make up FETS are defined. Examples demonstrate the way these tools integrate in order to perform the translation of Ada source to Petri-net format. The BIDS subsystem and, in particular, the use of tools and techniques to support user-directed, but transparent, searches of Ada-net reachability graphs are discussed. >

A Safe Regression Test Selection Technique for Web Services

Web applications and Web services have to undergo rapid modifications, and these modifications must be supported by rapid verification. While regression testing (RT) is a major component of most major testing systems, the related techniques have only just begun to be applied to Web services. One of the more important techniques, Regression test selection (RTS) aims to reduce the cost of performing RT. This paper reports a control flow graph-based approach that makes it possible to apply a safe RTS technique to Web services in an end-to-end manner. Safe RTS techniques ensure that no modification revealing tests will be left unselected. A simplified purchase order system that involves in three Web services is used to illustrate the use of our approach.

Towards automating regression test selection for web services

This paper reports a framework that makes it possible to carry out safe regression test selection for verification of Web services in an end-to-end manner. The Safe RTS technique has been integrated into a systematic method that monitors distributed code modifications and automates the RTS and RT processes. In doing so, a number of issues due to concurrent changes are recognized and solved.

Design strategies to improve performance of GIS Web services

GIS systems are ubiquitous distributed systems, since geo-spatial information adheres to almost everything. Considering the characteristics of GIS, the following four design-decision issues are particularly crucial: transactional mode (synchronous versus asynchronous), service granularity (finegrained versus coarse-grained), delivery manner (chunk versus stream), and transmission formats (GML versus binary). We have shared our experience in making choices in these four dimensions.

Web Services for Geographic Information Systems

A surge in Web services and applications for geographic information systems (GISs) has made large spatial-data archives available over the Internet. Significant accomplishments in GIS Web services have led to several exemplifying map and image services that adhere to Web services standards and provide geospatial data and digital maps to enterprise developers.

Applying Safe Regression Test Selection Techniques to Java Web Services

Existing safe regression test selection techniques, especially the white-box testing methods, do not work with Web service applications due to the inherent distributed nature of Web service systems. In this paper, we have presented a code transformation approach to regression test selection. The transformed code forms a local Java program which simulates the functionality and behavior of the Web service applications in an end-to-end manner. Safe regression test selection techniques can then be applied to the transformed code and safely reduce test cases for the Web service applications. A safe regression test selection technique has an additional quality in that it guarantees that nothing that could produce an error in the first set of tests will be left untested in the second set of tests under certain well-defined conditions. Additionally, we provide implementation details as well as an example

Concurrency Issues in Automating RTS for Web Services

Regression testing (RT), testing software with previously used test cases, is a mainstream practice in software maintenance. Regression test selection (RTS) is to reduce the number of tests which need to be retested. Safe RTS techniques add the assurance that no modification-revealing test case will be left unselected. Several effective safe RTS techniques were developed for traditional applications, but none of them can be directly applied to Web services, even though there have been RT tools and techniques for Web services test-case generation, and ranking competing services. We have developed an approach to adapt Rothermel and Harrolds safe RTS technique to Web services. This approach was designed to be automated. In doing so, we have recognized a set of challenging issues that arise as a result of multiple concurrent modifications in distributed, autonomous, but still interconnected services. We believe not only these issues are common to any automated RTS approach, the needs for the solutions to these issues will also become more and more keen as composite Web services are getting more and more ubiquitous.

A Shell-Neutral Modeling Approach Yields Sustainable Oyster Harvest Estimates: A Retrospective Analysis of the Louisiana State Primary Seed Grounds

ABSTRACT A numerical model is presented that defines a sustainability criterion as no net loss of shell, and calculates a sustainable harvest of seed (<75 mm) and sack or market oysters (≥75 mm). Stock assessments of the Primary State Seed Grounds conducted east of the Mississippi from 2009 to 2011 show a general trend toward decreasing abundance of sack and seed oysters. Retrospective simulations provide estimates of annual sustainable harvests. Comparisons of simulated sustainable harvests with actual harvests show a trend toward unsustainable harvests toward the end of the time series. Stock assessments combined with shell-neutral models can be used to estimate sustainable harvest and manage cultch through shell planting when actual harvest exceeds sustainable harvest. For exclusive restoration efforts (no fishing allowed), the model provides a metric for restoration success—namely, shell accretion. Oyster fisheries that remove shell versus reef restorations that promote shell accretion, although divergent in their goals, are convergent in their management; both require vigilant attention to shell budgets.

Achieving interoperability for integration of heterogeneous COTS geographic information systems

Using multiple commercial off-the-shelf (COTS) GIS suites is a common phenomenon, because different COTS products often have different strengths in various applications. On the other hand, deploying heterogeneous GIS software has the tendency to form fragmented data sets and to cause inconsistency. Data consolidation is an effective way to preserve data integrity. To accomplish this, we must achieve interoperability between different GIS tools. While vector spatial data have the standard database models to support interoperability, raster based images have been conventionally managed as files. Compared to the database approach, the file-based management for raster data is disadvantageous in terms of performance and flexibility. We implemented an adapter that allowed the file-based GIS tools to access the raster data storage in databases managed by a COTS software product. To integrate the COTS GIS into the Java 2 Platform Enterprise Edition (J2EE) framework, we have further enhanced this adapter and made it compliant to the J2EE Connector Architecture (J2EE-CA) standard. Using this kind of J2EE-CA adapter, any GIS can be managed by any J2EE server. The J2EE framework is an ideal foundation for building enterprise-wide geographic information systems.