A flexible, policy-aware middleware system

Middleware;Electronic data processing--Distributed processing

Walker, Scott Mervyn ; Dearle, Alan ; Dearle, Alan

University:University of St Andrews

Department:Computer Science (School of)

关键词: Middleware;    Electronic data processing--Distributed processing;   

Others  :  https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/154/ScottMervynWalkerPhDThesis.pdf?sequence=6&isAllowed=y

来源: DR-NTU

【 摘 要 】

Middleware augments operating systems and network infrastructure to assist inthe creation of distributed applications in a heterogeneous environment. Currentmiddleware systems exhibit some or all of the following five main problems:1. Decisions must be made early in the design process.2. Applications are inflexible to dynamic changes in their distribution.3. Application development is complex and error-prone.4. Existing systems force an unnatural encoding of application-level semantics.5. Approaches to the specification of distribution policy are limited.This thesis defines a taxonomy of existing middleware systems and describes theirlimitations. The requirements that must be met by a third generation middleware systemare defined and implemented by a system called the RAFDA Run-Time (RRT). The RRTallows control over the extent to which inter-address-space communication is exposed toprogrammers, aiding the creation, maintenance and evolution of distributed applications.The RRT permits the introduction of distribution into applications quickly andwith minimal programmer effort, allowing for quick application prototyping.Programmers can conceal or expose the distributed nature of applications as required. The RRT allows instances of arbitrary application classes to be exposed to remote access as Web Services, provides control over the parameter-passing semantics applied to remote method calls and permits the creation of flexible distribution policies. The design of the RRT is described and evaluated qualitatively in the context of a case study based around the implementation of a peer-to-peer overlay network. A prototype implementation of the RRT is examined and evaluated quantitatively.Programmers determine the trade off between flexibility and simplicity offered bythe RRT on a per-application basis, by concealing or exposing inter-address-spacecommunication. The RRT is a middleware system that adapts to the needs of applications, rather than forcing distributed applications to adapt to the needs of the middleware system.