Showing papers in "IEEE Transactions on Software Engineering in 2003"

An empirical study of speed and communication in globally distributed software development

Abstract: Global software development is rapidly becoming the norm for technology companies. Previous qualitative research suggests that distributed development may increase development cycle time for individual work items (modification requests). We use both data from the source code change management system and survey data to model the extent of delay in a distributed software development organization and explore several possible mechanisms for this delay. One key finding is that distributed work items appear to take about two and one-half times as long to complete as similar items where all the work is colocated. The data strongly suggest a mechanism for the delay, i.e., that distributed work items involve more people than comparable same-site work items, and the number of people involved is strongly related to the calendar time to complete a work item. We replicate the analysis of change data in a different organization with a different product and different sites and confirm our main findings. We also report survey results showing differences between same-site and distributed social networks, testing several hypotheses about characteristics of distributed social networks that may be related to delay. We discuss implications of our findings for practices and collaboration technology that have the potential for dramatically speeding distributed software development.

Model-checking algorithms for continuous-time Markov chains

Abstract: Continuous-time Markov chains (CTMCs) have been widely used to determine system performance and dependability characteristics. Their analysis most often concerns the computation of steady-state and transient-state probabilities. This paper introduces a branching temporal logic for expressing real-time probabilistic properties on CTMCs and presents approximate model checking algorithms for this logic. The logic, an extension of the continuous stochastic logic CSL of Aziz et al. (1995, 2000), contains a time-bounded until operator to express probabilistic timing properties over paths as well as an operator to express steady-state probabilities. We show that the model checking problem for this logic reduces to a system of linear equations (for unbounded until and the steady-state operator) and a Volterra integral equation system (for time-bounded until). We then show that the problem of model-checking time-bounded until properties can be reduced to the problem of computing transient state probabilities for CTMCs. This allows the verification of probabilistic timing properties by efficient techniques for transient analysis for CTMCs such as uniformization. Finally, we show that a variant of lumping equivalence (bisimulation), a well-known notion for aggregating CTMCs, preserves the validity of all formulas in the logic.

Key establishment in large dynamic groups using one-way function trees

Abstract: We present, implement, and analyze a new scalable centralized algorithm, called OFT, for establishing shared cryptographic keys in large, dynamically changing groups. Our algorithm is based on a novel application of one-way function trees. In comparison with the top-down logical key hierarchy (LKH) method of Wallner et al., our bottom-up algorithm approximately halves the number of bits that need to be broadcast to members in order to rekey after a member is added or evicted. The number of keys stored by group members, the number of keys broadcast to the group when new members are added or evicted, and the computational efforts of group members, are logarithmic in the number of group members. Among the hierarchical methods, OFT is the first to achieve an approximate halving in broadcast length, an idea on which subsequent algorithms have built. Our algorithm provides complete forward and backward security: Newly admitted group members cannot read previous messages, and evicted members cannot read future messages, even with collusion by arbitrarily many evicted members. In addition, and unlike LKH, our algorithm has the option of being member contributory in that members can be allowed to contribute entropy to the group key. Running on a Pentium II, our prototype has handled groups with up to 10 million members. This algorithm offers a new scalable method for establishing group session keys for secure large-group applications such as broadcast encryption, electronic conferences, multicast sessions, and military command and control.

Empirical analysis of CK metrics for object-oriented design complexity: implications for software defects

Abstract: To produce high quality object-oriented (OO) applications, a strong emphasis on design aspects, especially during the early phases of software development, is necessary. Design metrics play an important role in helping developers understand design aspects of software and, hence, improve software quality and developer productivity. In this paper, we provide empirical evidence supporting the role of OO design complexity metrics, specifically a subset of the Chidamber and Kemerer (1991, 1994) suite (CK metrics), in determining software defects. Our results, based on industry data from software developed in two popular programming languages used in OO development, indicate that, even after controlling for the size of the software, these metrics are significantly associated with defects. In addition, we find that the effects of these metrics on defects vary across the samples from two programming languages-C++ and Java. We believe that these results have significant implications for designing high-quality software products using the OO approach.

Locating features in source code

Abstract: Understanding the implementation of a certain feature of a system requires identification of the computational units of the system that contribute to this feature. In many cases, the mapping of features to the source code is poorly documented. In this paper, we present a semiautomatic technique that reconstructs the mapping for features that are triggered by the user and exhibit an observable behavior. The mapping is in general not injective; that is, a computational unit may contribute to several features. Our technique allows for the distinction between general and specific computational units with respect to a given set of features. For a set of features, it also identifies jointly and distinctly required computational units. The presented technique combines dynamic and static analyses to rapidly focus on the system's parts that relate to a specific set of features. Dynamic information is gathered based on a set of scenarios invoking the features. Rather than assuming a one-to-one correspondence between features and scenarios as in earlier work, we can now handle scenarios that invoke many features. Furthermore, we show how our method allows incremental exploration of features while preserving the "mental map" the analyst has gained through the analysis.

CARISMA: context-aware reflective middleware system for mobile applications

Abstract: Mobile devices, such as mobile phones and personal digital assistants, have gained wide-spread popularity. These devices will increasingly be networked, thus enabling the construction of distributed applications that have to adapt to changes in context, such as variations in network bandwidth, battery power, connectivity, reachability of services and hosts, etc. In this paper, we describe CARISMA, a mobile computing middleware which exploits the principle of reflection to enhance the construction of adaptive and context-aware mobile applications. The middleware provides software engineers with primitives to describe how context changes should be handled using policies. These policies may conflict. We classify the different types of conflicts that may arise in mobile computing and argue that conflicts cannot be resolved statically at the time applications are designed, but, rather, need to be resolved at execution time. We demonstrate a method by which policy conflicts can be handled; this method uses a microeconomic approach that relies on a particular type of sealed-bid auction. We describe how this method is implemented in the CARISMA middleware architecture and sketch a distributed context-aware application for mobile devices to illustrate how the method works in practice. We show, by way of a systematic performance evaluation, that conflict resolution does not imply undue overheads, before comparing our research to related work and concluding the paper.

A simulation study of the model evaluation criterion MMRE

Abstract: The mean magnitude of relative error, MMRE, is probably the most widely used evaluation criterion for assessing the performance of competing software prediction models. One purpose of MMRE is to assist us to select the best model. In this paper, we have performed a simulation study demonstrating that MMRE does not always select the best model. Our findings cast some doubt on the conclusions of any study of competing software prediction models that use MMRE as a basis of model comparison. We therefore recommend not using MMRE to evaluate and compare prediction models. At present, we do not have any universal replacement for MMRE. Meanwhile, we therefore recommend using a combination of theoretical justification of the models that are proposed together with other metrics proposed in this paper.

Polymetric views - a lightweight visual approach to reverse engineering

Abstract: Reverse engineering software systems has become a major concern in software industry because of their sheer size and complexity. This problem needs to be tackled since the systems in question are of considerable worth to their owners and maintainers. In this article, we present the concept of a polymetric view, a lightweight software visualization technique enriched with software metrics information. Polymetric views help to understand the structure and detect problems of a software system in the initial phases of a reverse engineering process. We discuss the benefits and limits of several predefined polymetric views we have implemented in our tool CodeCrawler. Moreover, based on clusters of different polymetric views, we have developed a methodology which supports and guides a software engineer in the first phases of a reverse engineering of a large software system. We have refined this methodology by repeatedly applying it on industrial systems and illustrate it by applying a selection of polymetric views to a case study.

Test-suite reduction and prioritization for modified condition/decision coverage

Abstract: Software testing is particularly expensive for developers of high-assurance software, such as software that is produced for commercial airborne systems. One reason for this expense is the Federal Aviation Administration's requirement that test suites be modified condition/decision coverage (MC/DC) adequate. Despite its cost, there is evidence that MC/DC is an effective verification technique and can help to uncover safety faults. As the software is modified and new test cases are added to the test suite, the test suite grows and the cost of regression testing increases. To address the test-suite size problem, researchers have investigated the use of test-suite reduction algorithms, which identify a reduced test suite that provides the same coverage of the software according to some criterion as the original test suite, and test-suite prioritization algorithms, which identify an ordering of the test cases in the test suite according to some criteria or goals. Existing test-suite reduction and prioritization techniques, however, may not be effective in reducing or prioritizing MC/DC-adequate test suites because they do not consider the complexity of the criterion. This paper presents new algorithms for test-suite reduction and prioritization that can be tailored effectively for use with MC/DC. The paper also presents the results of empirical studies of these algorithms.

Event-based traceability for managing evolutionary change

Abstract: Although the benefits of requirements traceability are widely recognized, the actual practice of maintaining a traceability scheme is not always entirely successful. The traceability infrastructure underlying a software system tends to erode over its lifetime, as time-pressured practitioners fail to consistently maintain links and update impacted artifacts each time a change occurs, even with the support of automated systems. This paper proposes a new method of traceability based upon event-notification and is applicable even in a heterogeneous and globally distributed development environment. Traceable artifacts are no longer tightly coupled but are linked through an event service, which creates an environment in which change is handled more efficiently, and artifacts and their related links are maintained in a restorable state. The method also supports enhanced project management for the process of updating and maintaining the system artifacts.

Synthesis of behavioral models from scenarios

Abstract: Scenario-based specifications such as Message Sequence Charts (MSCs) are useful as part of a requirements specification. A scenario is a partial story, describing how system components, the environment, and users work concurrently and interact in order to provide system level functionality. Scenarios need to be combined to provide a more complete description of system behavior. Consequently, scenario synthesis is central to the effective use of scenario descriptions. How should a set of scenarios be interpreted? How do they relate to one another? What is the underlying semantics? What assumptions are made when synthesizing behavior models from multiple scenarios? In this paper, we present an approach to scenario synthesis based on a clear sound semantics, which can support and integrate many of the existing approaches to scenario synthesis. The contributions of the paper are threefold. We first define an MSC language with sound abstract semantics in terms of labeled transition systems and parallel composition. The language integrates existing approaches based on scenario composition by using high-level MSCs (hMSCs) and those based on state identification by introducing explicit component state labeling. This combination allows stakeholders to break up scenario specifications into manageable parts and reuse scenarios using hMCSs; it also allows them to introduce additional domain-specific information and general assumptions explicitly into the scenario specification using state labels. Second, we provide a sound synthesis algorithm which translates scenarios into a behavioral specification in the form of Finite Sequential Processes. This specification can be analyzed with the Labeled Transition System Analyzer using model checking and animation. Finally, we demonstrate how many of the assumptions embedded in existing synthesis approaches can be made explicit and modeled in our approach. Thus, we provide the basis for a common approach to scenario-based specification, synthesis, and analysis.

A unified scheme of some Nonhomogenous Poisson process models for software reliability estimation

Abstract: In this paper, we describe how several existing software reliability growth models based on Nonhomogeneous Poisson processes (NHPPs) can be comprehensively derived by applying the concept of weighted arithmetic, weighted geometric, or weighted harmonic mean. Furthermore, based on these three weighted means, we thus propose a more general NHPP model from the quasi arithmetic viewpoint. In addition to the above three means, we formulate a more general transformation that includes a parametric family of power transformations. Under this general framework, we verify the existing NHPP models and derive several new NHPP models. We show that these approaches cover a number of well-known models under different conditions.

Inference of message sequence charts

Abstract: Software designers draw message sequence charts for early modeling of the individual behaviors they expect from the concurrent system under design. Can they be sure that precisely the behaviors they have described are realizable by some implementation of the components of the concurrent system? If so, can we automatically synthesize concurrent state machines realizing the given MSCs? If, on the other hand, other unspecified and possibly unwanted scenarios are "implied" by their MSCs, can the software designer be automatically warned and provided the implied MSCs? In this paper, we provide a framework in which all these questions are answered positively. We first describe the formal framework within which one can derive implied MSCs and then provide polynomial-time algorithms for implication, realizability, and synthesis.

MobiPADS: a reflective middleware for context-aware mobile computing

Abstract: Traditionally, middleware technologies, such as CORBA, Java RMI, and Microsoft's DCOM, have provided a set of distributed computing services that essentially abstract the underlying network services to a monolithic "black box." In a mobile operating environment, the fundamental assumption of middleware abstracting a unified distributed service for all types of applications operating over a static network infrastructure is no longer valid. In particular, mobile applications are not able to leverage the benefits of adaptive computing to optimize its computation based on current contextual situations. In this paper, we introduce the Mobile Platform for Actively Deployable Service (MobiPADS) system. MobiPADS is designed to support context-aware processing by providing an executing platform to enable active service deployment and reconfiguration of the service composition in response to environments of varying contexts. Unlike most mobile middleware, MobiPADS supports dynamic adaptation at both the middleware and application layers to provide flexible configuration of resources to optimize the operations of mobile applications. Within the MobiPADS system, services (known as mobilets) are configured as chained service objects to provide augmented services to the underlying mobile applications so as to alleviate the adverse conditions of a wireless environment.

Context-aware middleware for resource management in the wireless Internet

Abstract: The provisioning of Web services over the wireless Internet introduces novel challenging issues for service design and implementation: from user/terminal mobility during service execution, to wide heterogeneity of portable access devices and unpredictable modifications in accessible resources. In this scenario, there are frequent provision-time changes in the context, defined as the logical set of accessible resources depending on client location, access terminal capabilities, and system/service management policies. The development of context-dependent services requires novel middlewares with full context visibility. We propose a middleware for context-aware resource management, called CARMEN, capable of supporting the automatic reconfiguration of wireless Internet services in response to context changes without any intervention on the service logic. CARMEN determines the context on the basis of metadata, which include declarative management policies and profiles for user preferences, terminal capabilities, and resource characteristics. In addition, CARMEN exploits the mobile agent technology to implement mobile middleware components that follow the provision-time movement of clients to support locally their customized service access. The proposed middleware shows how metadata and mobile agents can favor component reusability and automatic service reconfiguration, by reducing the development/ deployment complexity.

Design and evaluation of a support service for mobile, wireless publish/subscribe applications

Abstract: This paper presents the design and evaluation of a support service for mobile, wireless clients of a distributed publish/subscribe system. A distributed publish/subscribe system is a networked communication infrastructure where messages are published by senders and then delivered to the receivers whose subscriptions match the messages. Communication therefore does not involve the use of explicit addresses, but rather emerges from the dynamic arrangement of publishers and subscribers. Such a communication mechanism is an ideal platform for a variety of Internet applications, including multiparty messaging, personal information management, information sharing, online news distribution, service discovery, and electronic auctions. Our goal is to support such applications on mobile, wireless host devices in such a way that the applications can, if they chose, be oblivious to the mobility and intermittent connectivity of their hosts as they move from one publish/subscribe access point to another. In this paper, we describe a generic, value-added service that can be used in conjunction with publish/subscribe systems to achieve these goals. We detail the implementation of the service and present the results of our evaluation of the service in both wireline and emulated wireless environments.

A scenario-driven approach to trace dependency analysis

Abstract: Software development artifacts-such as model descriptions, diagrammatic languages, abstract (formal) specifications, and source code-are highly interrelated where changes in some of them affect others. Trace dependencies characterize such relationships abstractly. This paper presents an automated approach to generating and validating trace dependencies. It addresses the severe problem that the absence of trace information or the uncertainty of its correctness limits the usefulness of software models during software development. It also automates what is normally a time consuming and costly activity due to the quadratic explosion of potential trace dependencies between development artifacts.

Using a concept lattice of decomposition slices for program understanding and impact analysis

Abstract: The decomposition slice graph and concept lattice are two program representations used to abstract the details of code into a higher-level view of the program. The decomposition slice graph partitions the program into computations performed on different variables and shows the dependence relation between computations, holding when a computation needs another computation as a building block. The concept lattice groups program entities which share common attributes and organizes such groupings into a hierarchy of concepts, which are related through generalizations/specializations. This paper investigates the relationship existing between these two program representations. The main result of this paper is a novel program representation, called concept lattice of decomposition slices, which is shown to be an extension of the decomposition slice graph, and is obtained by means of concept analysis, with additional nodes associated with weak interferences between computations, i.e., shared statements which are not decomposition slices. The concept lattice of decomposition slices can be used to support software maintenance by providing relevant information about the computations performed by a program and the related dependences/interferences, as well as by representing a natural data structure on which to conduct impact analysis. Preliminary results on small to medium size code support the applicability of this method at the intraprocedural level or when investigating the dependences among small groups of procedures.

Architectural-level risk analysis using UML

Abstract: Risk assessment is an essential part in managing software development. Performing risk assessment during the early development phases enhances resource allocation decisions. In order to improve the software development process and the quality of software products, we need to be able to build risk analysis models based on data that can be collected early in the development process. These models will help identify the high-risk components and connectors of the product architecture, so that remedial actions may be taken in order to control and optimize the development process and improve the quality of the product. In this paper, we present a risk assessment methodology which can be used in the early phases of the software life cycle. We use the Unified Modeling Language (UML) and commercial modeling environment Rational Rose Real Time (RoseRT) to obtain UML model statistics. First, for each component and connector in software architecture, a dynamic heuristic risk factor is obtained and severity is assessed based on hazard analysis. Then, a Markov model is constructed to obtain scenarios risk factors. The risk factors of use cases and the overall system risk factor are estimated using the scenarios risk factors. Within our methodology, we also identify critical components and connectors that would require careful analysis, design, implementation, and more testing effort. The risk assessment methodology is applied on a pacemaker case study.

Predicting maintenance performance using object-oriented design complexity metrics

Abstract: The Object-Oriented (OO) paradigm has become increasingly popular in recent years. Researchers agree that, although maintenance may turn out to be easier for OO systems, it is unlikely that the maintenance burden will completely disappear. One approach to controlling software maintenance costs is the utilization of software metrics during the development phase, to help identify potential problem areas. Many new metrics have been proposed for OO systems, but only a few of them have been validated. The purpose of this research is to empirically explore the validation of three existing OO design complexity metrics and, specifically, to assess their ability to predict maintenance time. This research reports the results of validating three metrics, Interaction Level (IL), Interface Size (IS), and Operation Argument Complexity (OAC). A controlled experiment was conducted to investigate the effect of design complexity (as measured by the above metrics) on maintenance time. Each of the three metrics by itself was found to be useful in the experiment in predicting maintenance performance.

An experimental comparison of usage-based and checklist-based reading

Abstract: Software quality can be defined as the customers' perception of how a system works. Inspection is a method to monitor and control the quality throughout the development cycle. Reading techniques applied to inspections help reviewers to stay focused on the important parts of an artifact when inspecting. However, many reading techniques focus on finding as many faults as possible, regardless of their importance. Usage-based reading helps reviewers to focus on the most important parts of a software artifact from a user's point of view. We present an experiment, which compares usage-based and checklist-based reading. The results show that reviewers applying usage-based reading are more efficient and effective in detecting the most critical faults from a user's point of view than reviewers using checklist-based reading. Usage-based reading may be preferable for software organizations that utilize or start utilizing use cases in their software development.

An empirical validation of object-oriented metrics in two different iterative software processes

Abstract: Object-oriented (OO) metrics are used mainly to predict software engineering activities/efforts such as maintenance effort, error proneness, and error rate. There have been discussions about the effectiveness of metrics in different contexts. In this paper, we present an empirical study of OO metrics in two iterative processes: the short-cycled agile process and the long-cycled framework evolution process. We find that OO metrics are effective in predicting design efforts and source lines of code added, changed, and deleted in the short-cycled agile process and ineffective in predicting the same aspects in the long-cycled framework process. This leads us to believe that OO metrics' predictive capability is limited to the design and implementation changes during the development iterations, not the long-term evolution of an established system in different releases.

Strategies for software reuse: a principal component analysis of reuse practices

Abstract: This research investigates the premise that the likelihood of success of software reuse efforts may vary with the reuse strategy employed and, hence, potential reuse adopters must be able to understand reuse strategy alternatives and their implications. We use survey data collected from 71 software development groups to empirically develop a set of six dimensions that describe the practices employed in reuse programs. The study investigates the patterns in which these practices co-occur in the real world, demonstrating that the dimensions cluster into five distinct reuse strategies, each with a different potential for reuse success. The findings provide a means to classify reuse settings and assess their potential for success.

Using spanning sets for coverage testing

Abstract: A test coverage criterion defines a set E/sub r/ of entities of the program flowgraph and requires that every entity in this set is covered under some test Case. Coverage criteria are also used to measure the adequacy of the executed test cases. In this paper, we introduce the notion of spanning sets of entities for coverage testing. A spanning set is a minimum subset of E/sub r/, such that a test suite covering the entities in this subset is guaranteed to cover every entity in E/sub r/. When the coverage of an entity always guarantees the coverage of another entity, the former is said to subsume the latter. Based on the subsumption relation between entities, we provide a generic algorithm to find spanning sets for control flow and data flow-based test coverage criteria. We suggest several useful applications of spanning sets: They help reduce and estimate the number of test cases needed to satisfy coverage criteria. We also empirically investigate how the use of spanning sets affects the fault detection effectiveness.

A study of the effect of imperfect debugging on software development cost

Abstract: It is widely recognized that the debugging processes are usually imperfect. Software faults are not completely removed because of the difficulty in locating them or because new faults might be introduced. Hence, it is of great importance to investigate the effect of the imperfect debugging on software development cost, which, in turn, might affect the optimal software release time or operational budget. In this paper, a commonly used cost model is extended to the case of imperfect debugging. Based on this, the effect of imperfect debugging is studied. As the probability of perfect debugging, termed testing level here, is expensive to be increased, but manageable to a certain extent with additional resources, a model incorporating this situation is presented. Moreover, the problem of determining the optimal testing level is considered. This is useful when the decisions regarding the test team composition, testing strategy, etc., are to be made for more effective testing.

An investigation of graph-based class integration test order strategies

Abstract: The issue of ordering class integration in the context of integration testing has been discussed by a number of researchers. More specifically, strategies have been proposed to generate a test order while minimizing stubbing. Recent papers have addressed the problem of deriving an integration order in the presence of dependency cycles in the class diagram. Such dependencies represent a practical problem as they make any topological ordering of classes impossible. Three main approaches, aimed at "breaking" cycles, have been proposed. The first one was proposed by Tai and Daniels (1999) and is based on assigning a higher-level order according to aggregation and inheritance relationships and a lower-level order according to associations. The second one was proposed by Le Traon et al. (2000) and is based on identifying strongly connected components in the dependency graph. The third one was proposed by Briand et al. (2000); it combines some of the principles of the two previous approaches and addresses some of their shortcomings (e.g., the first approach may result into unnecessary stubbing whereas the second may lead to breaking cycles by "removing" aggregation or inheritance dependencies, thus leading to complex stubbing). This paper reviews these strategies (principles are described, advantages and drawbacks are precisely investigated) and provides both analytical and empirical comparisons based on five case studies.

A ranking of software engineering measures based on expert opinion

Abstract: This research proposes a framework based on expert opinion elicitation, developed to select the software engineering measures which are the best software reliability indicators. The current research is based on the top 30 measures identified in an earlier study conducted by Lawrence Livermore National Laboratory. A set of ranking criteria and their levels were identified. The score of each measure for each ranking criterion was elicited through expert opinion and then aggregated into a single score using multiattribute utility theory. The basic aggregation scheme selected was a linear additive scheme. A comprehensive sensitivity analysis was carried out. The sensitivity analysis included: variation of the ranking criteria levels, variation of the weights, variation of the aggregation schemes. The top-ranked measures were identified. Use of these measures in each software development phase can lead to a more reliable quantitative prediction of software reliability.

Formalization of the Whole-Part relationship in the Unified Modeling Language

Abstract: A formal definition for the semantics of the Whole-Part relationship in the Unified Modeling Language or UML is introduced. This provides a fully directly usable specification which can be incorporated into version 2.0 of UML. An improvement to the current metamodel fragment relating to relationships is proposed, supplemented by the introduction of axioms expressed in the Object Constraint Language or OCL. The overall formalization relates to a clear and concise emphasis on carefully enunciated (primary) characteristics that apply to all instances of a new Whole-Part metatype. Specific kinds of the Whole-Part relationship are defined in terms of secondary characteristics, which must be possessed by subtypes: In UML 1.4, these are Aggregation (a.k.a. white diamond) and Composition (a.k.a. black diamond). Primary and secondary characteristics may then be consistently combined with each other. Consequently, this allows the possible introduction of supplementary forms of Whole-Part. Such a revision is necessary since Aggregation and Composition in UML 1.4 do not cover the full spectrum of Whole-Part theory.

Foundations of sequence-based software specification

Abstract: Rigorous specification early in the software development process can greatly reduce the cost of later development and maintenance, as well as provide an explicit means to manage risk and identify and meet safety requirements. Sequence-based software specification is a collection of techniques for implementing rigorous, practical software specification. The primary result of this research is the sequence enumeration method of specification writing. Straightforward, systematic enumeration of all sequences to produce an arguably complete, consistent, and traceably correct specification is made practical by controlling the growth of the process.

A testing framework for mobile computing software

Abstract: We present a framework for testing applications for mobile computing devices. When a device is moved into and attached to a new network, the proper functioning of applications running on the device often depends on the resources and services provided locally in the current network. This framework provides an application-level emulator for mobile computing devices to solve this problem. Since the emulator is constructed as a mobile agent, it can carry applications across networks on behalf of its target device and allow the applications to connect to local servers in its current network in the same way as if they had been moved with and executed on the device itself. This paper also demonstrates the utility of this framework by describing the development of typical network-dependent applications in mobile and ubiquitous computing settings.