Integrated Java Bytecode Verification

AbstractExisting Java verifiers perform an iterative data-flow analysis to discover the unambiguous type of values stored on the stack or in registers. Our novel verification algorithm uses abstract interpretation to obtain definition/use information for each register and stack location in the program, which in turn is used to transform the program into Static Single Assignment form. In SSA, verification is reduced to simple type compatibility checking between the definition type of each SSA variable and the type of each of its uses. Inter-adjacent transitions of a value through stack and registers are no longer verified explicitly. This integrated approach is more efficient than traditional bytecode verification but still as safe as strict verification, as overall program correctness can be induced once the data flow from each definition to all associated uses is known to be type-safe

Flexible Bindings for Type-Safe Embedded Operating Systems.

This paper presents the binding model implemented in Camille, an extensible operating system for resource-limited devices. Modern embedded systems need on the first hand to fully exploit the limited hardware on which they run and on the other hand to dynamically adapt themselves to changes in their runtime environment. Camille is an exokernel which support static customization of components and dynamic loading of system extensions. Dynamic kernel and application adaptation is implemented by an inter-component communication model. This model is based on flexible bindings which permit to fully customize the way components interact with each others. Bindings can be static, virtual or compiled to guarantee performances of inter-component communications. This paper shows that it is possible to build a flexible operating system without sacrificing runtime performances, even for devices as constrained as smart cards. We first present the architecture of the Camille exokernel and the intermediate language Facade into which applications and system components are translated to ease type verification. We then describe the component model implemented in Camille and the inter-component communication scheme based on embedded binding factories. We then details the binding generation process and the various verifications which can be enforced when implementing bindings. We present some experimental results we have obtained when monitoring the performances of our native code generator. Finally, we conclude and discuss the future work we plan to conduct concerning extraction of selected properties from generated code

The Omnibus language and integrated verification approach

This thesis describes the Omnibus language and its supporting framework of tools. Omnibus is an object-oriented language which is superficially similar to the Java programming language but uses value semantics for objects and incorporates a behavioural interface specification language. Specifications are defined in terms of a subset of the query functions of the classes for which a frame-condition logic is provided. The language is well suited to the specification of modelling types and can also be used to write implementations. An overview of the language is presented and then specific aspects such as subtleties in the frame-condition logic, the implementation of value semantics and the role of equality are discussed. The challenges of reference semantics are also discussed. The Omnibus language is supported by an integrated verification tool which provides support for three assertion-based verification approaches: run-time assertion checking, extended static checking and full formal verification. The different approaches provide different balances between rigour and ease of use. The Omnibus tool allows these approaches to be used together in different parts of the same project. Guidelines are presented in order to help users avoid conflicts when using the approaches together. The use of the integrated verification approach to meet two key requirements of safe software component reuse, to have clear descriptions and some form of certification, are discussed along with the specialised facilities provided by the Omnibus tool to manage the distribution of components. The principles of the implementation of the tool are described, focussing on the integrated static verifier module that supports both extended static checking and full formal verification through the use of an intermediate logic. The different verification approaches are used to detect and correct a range of errors in a case study carried out using the Omnibus language. The case study is of a library system where copies of books, CDs and DVDs are loaned out to members. The implementation consists of 2278 lines of Omnibus code spread over 15 classes. To allow direct comparison of the different assertion-based verification approaches considered, run-time assertion checking, extended static checking and then full formal verification are applied to the application in its entirety. This directly illustrates the different balances between error coverage and ease-of-use which the approaches offer. Finally, the verification policy system is used to allow the approaches to be used together to verify different parts of the application

Towards an aspect weaving BPEL engine

This position paper proposes the use of dynamic aspects and the visitor design pattern to obtain a highly configurable and extensible BPEL engine. Using these two techniques, the core of this infrastructural software can be customised to meet new requirements and add features such as debugging, execution monitoring, or changing to another Web Service selection policy. Additionally, it can easily be extended to cope with customer-specific BPEL extensions. We propose the use of dynamic aspects not only on the engine itself but also on the workflow in order to tackle the problems of Web Service hot deployment and hot fixes to long running processes. In this way, composing aWeb Service "on-the-fly" means weaving its choreography interface into the workflow

Journal of Telecommunications and Information Technology, 2002, nr 4

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