A development framework for artificial intelligence based distributed operations support systems

Advanced automation is required to reduce costly human operations support requirements for complex space-based and ground control systems. Existing knowledge based technologies have been used successfully to automate individual operations tasks. Considerably less progress has been made in integrating and coordinating multiple operations applications for unified intelligent support systems. To fill this gap, SOCIAL, a tool set for developing Distributed Artificial Intelligence (DAI) systems is being constructed. SOCIAL consists of three primary language based components defining: models of interprocess communication across heterogeneous platforms; models for interprocess coordination, concurrency control, and fault management; and for accessing heterogeneous information resources. DAI applications subsystems, either new or existing, will access these distributed services non-intrusively, via high-level message-based protocols. SOCIAL will reduce the complexity of distributed communications, control, and integration, enabling developers to concentrate on the design and functionality of the target DAI system itself

On the complexity of concurrency control by locking in distributed database systems

Given a pair of locked transactions, accessing a distributed database, the problem is studied of whether this pair is safe, i.e., guaranteed to produce only serializable schedules. It is shown that an easy-to-test graph condition, which characterizes safety for a pair of locked transactions in a centralized database, also applies when the database has been distributed among at most three sites

Virtual Machine Support for Many-Core Architectures: Decoupling Abstract from Concrete Concurrency Models

The upcoming many-core architectures require software developers to exploit concurrency to utilize available computational power. Today's high-level language virtual machines (VMs), which are a cornerstone of software development, do not provide sufficient abstraction for concurrency concepts. We analyze concrete and abstract concurrency models and identify the challenges they impose for VMs. To provide sufficient concurrency support in VMs, we propose to integrate concurrency operations into VM instruction sets. Since there will always be VMs optimized for special purposes, our goal is to develop a methodology to design instruction sets with concurrency support. Therefore, we also propose a list of trade-offs that have to be investigated to advise the design of such instruction sets. As a first experiment, we implemented one instruction set extension for shared memory and one for non-shared memory concurrency. From our experimental results, we derived a list of requirements for a full-grown experimental environment for further research

A distributed file service based on optimistic concurrency control

The design of a layered file service for the Amoeba Distributed System is discussed, on top of which various applications can easily be intplemented. The bottom layer is formed by the Amoeba Block Services, responsible for implementing stable storage and repficated, highly available disk blocks. The next layer is formed by the Amoeba File Service which provides version management and concurrency control for tree-structured files. On top of this layer, the appficafions, ranging from databases to source code control systems, determine the structure of the file trees and provide an interface to the users