Agents are problem-solving entities that can be used to develop complex and distributed systems because they are autonomous, mobile, reactive, social, and proactive. Today's trends in agent technology include the ...
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Agents are problem-solving entities that can be used to develop complex and distributed systems because they are autonomous, mobile, reactive, social, and proactive. Today's trends in agent technology include the development of applications as multi-agent systems, where several agents interact within the same application. In these systems, the interactions among agents must be carefully considered. Roles constitute a powerful paradigm for modeling interactions, allowing algorithmic issues and interaction-dependent issues to be handled independently. In this paper, we present the RoleX interaction infrastructure, which enables java(TM) agents to dynamically assume and use roles at runtime. Our approach is based on using bytecode manipulation to add (or remove) java members from agents, changing their capabilities. We detail the main component of RoleX, the Role Loader, which performs the bytecode manipulation that allows agents to dynamically assume and release roles.
The Real-Time Specification for java (RTSJ) provides an integrated approach to scheduling periodic real-time threads and monitoring their CPU execution time. It defines a cost enforcement model whereby a periodic real...
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The Real-Time Specification for java (RTSJ) provides an integrated approach to scheduling periodic real-time threads and monitoring their CPU execution time. It defines a cost enforcement model whereby a periodic real-time thread is suspended when it consumes more CPU time (budget) than it requested in a single release. However, compliant implementations need not support this model, as the underlying operating systems mechanisms are not widely available. Consequently, experience with the model is limited (it is generally not provided in most implementations of the RTSJ). In previous work we showed, using model checking techniques, that the current version of the cost enforcement model can, under certain unlikely scenarios, allow a periodic thread more than its CPU budget in a single period. Such a behaviour can undermine any schedulability analysis that has been undertaken. In this paper, we present a revised formal model, which corrects this anomalous behaviour, and evaluate its properties. We also extend the formal model, so it allows support for real-time threads with sporadic and aperiodic releases, and show how our revised cost enforcement model is valid for all types of threads.
One approach to model checking program source code is to view a model checker as a target machine. In this setting, program source code is translated to a model checker's input language using a process that shares...
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One approach to model checking program source code is to view a model checker as a target machine. In this setting, program source code is translated to a model checker's input language using a process that shares much in common with program compilation. For example, well-defined intermediate program representations are used to stage the translation through a series of analyses and optimizing transformations and target-specific details are isolated in code generation modules. In this paper, we present the Bandera Intermediate Representation (BIR)-a guarded-assignment transformation system language that has been designed to support the translation of java programs to a variety of model checkers. BIR includes constructs, such as inheritance, dynamic creation of data, and locking primitives, that are designed to model the semantics of java primitives. BIR also includes several non-deterministic choice constructs that support abstraction in modeling and specification of properties of dynamic heap structures. We have developed a BIR-based tool infrastructure that has been applied to develop customized analysis frameworks for several different input languages using different model checking tools. We present BIR's type system and operational semantics in sufficient detail to support similar applications by other researchers. This semantics details several state space reductions and state space search variations. We describe the translation of java to BIR and how BIR is translated to the input languages of several model checkers.
This is a study of the performance progress of the SanFrancisco(TM) project from the time the decision was made to base it on the java(TM) language up to the time SanFrancisco applications were successfully deployed i...
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This is a study of the performance progress of the SanFrancisco(TM) project from the time the decision was made to base it on the java(TM) language up to the time SanFrancisco applications were successfully deployed in the marketplace-from February 1997 until late 1999. We document the challenges, decisions, and technologies that were encountered during the three-year development period that saw performance improve by orders of magnitude. Key areas that allowed us to achieve this improvement were intelligent object caching, improved object access strategies use of commands (function shipping), efficient mapping of objects to the underlying database, appropriate usage of java, programmer education, and acquiring (or building) needed tools. We also discuss several areas where challenges remain and more progress is needed.
As the use of the java(TM) language and virtual machines proliferates beyond the sphere of applets into the space of server programs, developers are requiring better performance, availability, and transactional and sc...
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As the use of the java(TM) language and virtual machines proliferates beyond the sphere of applets into the space of server programs, developers are requiring better performance, availability, and transactional and scalability features. This paper describes the work done for the Operating System/390 (OS/390(R)) java virtual machine to improve performance and serviceability, to introduce security and performance enhancements, and to redesign parts of the virtual machine to enable it to run server programs efficiently and safely. Although OS/390 was the motivating platform for these changes, java server programs on any platform can benefit from these features.
Non-interference guarantees the absence of illicit information flow throughout program execution. It can be enforced by appropriate information flow type systems. Much of the previous work on type systems for non-inte...
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Non-interference guarantees the absence of illicit information flow throughout program execution. It can be enforced by appropriate information flow type systems. Much of the previous work on type systems for non-interference has focused on calculi or high-level programminglanguages, and existing type systems for low-level languages typically omit objects, exceptions and method calls. We define an information flow type system for a sequential JVM-like language that includes all these programming features, and we prove, in the Coq proof assistant, that it guarantees non-interference. An additional benefit of the formalisation is that we have extracted from our proof a certified lightweight bytecode verifier for information flow. Our work provides, to the best of our knowledge, the first sound and certified information flow type system for such an expressive fragment of the JVM.
We present the java(TM) Virtual Machine Profiler Interface (JVMPI), which defines a general-purpose and portable mechanism for obtaining comprehensive profiling data from the java virtual machine. Vile show that it is...
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We present the java(TM) Virtual Machine Profiler Interface (JVMPI), which defines a general-purpose and portable mechanism for obtaining comprehensive profiling data from the java virtual machine. Vile show that it is extensible, nonintrusive, and powerful enough to suit the needs of different profilers and virtual machine implementations. With the JVMPI, most profiler vendors will not need to build custom instrumentation in the java virtual machine, in addition, we solve challenges to profiler design and implementation posed by the multithreading and garbage collection support provided by the java virtual machine. Profilers based on the JVMPI can produce thread-aware CPU time profiles, uncover heavy memory allocation sites, detect unnecessary object retention, pinpoint scalability problems caused by high monitor contention, reveal thread deadlocks, and perform interactive profiling with minimum overhead. We also describe HPROF, a profiler based on JVMPI, developed by us to demonstrate the power of JVMPI.
In java, an interface specifies public abstract methods and associated public constants. Conformance of a class to an interface is by name. We propose to allow structural conformance to interfaces: any class or interf...
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In java, an interface specifies public abstract methods and associated public constants. Conformance of a class to an interface is by name. We propose to allow structural conformance to interfaces: any class or interface that declares or implements each method in a target interface conforms structurally to the interface, and any expression of the source class or interface type can be used where a value of the target interface type is expected. We argue that structural conformance results in a major gain in flexibility in situations that require retroactive abstraction over types. Structural conformance requires no additional syntax and only small modifications to the java compiler and optionally, for performance reasons, the virtual machine, resulting in a minor performance penalty. Our extension is type-safe: a cast-free program that compiles without errors will not have any type errors at run time. Our extension is conservative: existing java programs still compile and run in the same manner as under the original language definition. Finally, structural conformance works well with recent extensions such as java remote method invocation. We have implemented our extension of java with structural interface conformance by modifying the java Developers Kit 1.1.5 source release for Solaris and Windows 95/NT. We have also created a test suite for the extension.
Background: The integration of many aspects of protein/DNA structure analysis is an important requirement for software products in general area of structural bioinformatics. In fact, there are too few software package...
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Background: The integration of many aspects of protein/DNA structure analysis is an important requirement for software products in general area of structural bioinformatics. In fact, there are too few software packages on the internet which can be described as successful in this respect. We might say that what is still missing is publicly available, web based software for interactive analysis of the sequence/structure/ function of proteins and their complexes with DNA and ligands. Some of existing software packages do have certain level of integration and do offer analysis of several structure related parameters, however not to the extent generally demanded by a user. Results: We are reporting here about new Sting Millennium Suite (SMS) version which is fully accessible ( including for local files at client end), web based software for molecular structure and sequence/structure/ function analysis. The new SMS client version is now operational also on Linux boxes and it works with non-public pdb formatted files (structures not deposited at the RCSB/ PDB), eliminating earlier requirement for the registration if SMS components were to be used with user's local files. At the same time the new SMS offers some important additions and improvements such as link to ProTherm as well as significant re-engineering of SMS component ConSSeq. Also, we have added 3 new SMS mirror sites to existing network of global SMS servers: Argentina, Japan and Spain. Conclusion: SMS is already established software package and many key data base and software servers worldwide, do offer either a link to, or host the SMS. SMS ((s) under bar ting (m) under bar illennium (s) under bar uite) is web-based publicly available software developed to aid researches in their quest for translating information about the structures of macromolecules into knowledge. SMS allows to a user to interactively analyze molecular structures, cross-referencing visualized information with a correlated one, available acro
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