Synchronization of Multiple Agents in Rule-Based Development Environments

The Rule-Based Development Environment (RBDE) is recently-developed approach for providing intelligent assistance to developers working on a large-scale software projects. RBDEs model the development process in terms of rules, and then enact this model by automatically firing rules at the appropriate time. The RBDE approach has been used to develop single-user environment, but support for multiple developers cooperating on the same project is still not available because of the lack of mechanisms that can synchronize the efforts of multiple developers, who concurrently select commands, causing the firing of multiple rules (either directly or via chaining) that concurrently access shared data. Conflicts between different rules and concurrent .access to shared data may cause the violation of consistency in the project database, and thus necessitate the synchronization of concurrent activities. The conjecture of this proposal is that an RBDE can provide the required synchronization if it is provided with knowledge about what it means for the data of a specific project to be in a consistent state, and about the semantics of operations that developers perform on the data. The research that this paper proposes will formulate a frame work for specifying consistency of data in an RBDE, and formulate a mechanism for synchronizing the actions of concurrent rules fired on behalf of multiple developers cooperating on a common or different tasks

Concurrency Control in Rule-Based Software Development Environments

This dissertation investigates the concurrency control problem in software development environments (SDEs). The problem arises when multiple developers perform activities that concurrently access the project's components, stored as database objects. The interleaved execution of the developers' activities leads to interference if they access overlapping sets of objects concurrently. An SDE can ensure that activities never interfere by modeling their execution in terms of atomic transactions and allowing only serializable schedules. This prevents cooperation, which requires some degree of interference between the activities of multiple developers. To allow cooperation, an SDE must be provided with semantic information about development activities. In rule-based SDEs, the necessary information is readily available in the set of rules that defines the process model of a project. The rules are loaded into the SDE, which provides process-specific assistance through a rule chaining engine. A single user command might lead the chaining engine to initiate a rule chain. The concurrency control problem in rule-based SDEs manifests itself in terms of interference between concurrent rule chains. We present a mechanism that extracts semantic information from the process model to solve the concurrency control problem without obstructing cooperation. The mechanism is composed of two modules: (1) a conflict detection module, which models activities as nested transactions and uses two-phase locking to detect interference; and (2) a conflict resolution module, which employs two protocols to resolve interference. The first protocol, seep, uses the process model to implement a priority-based scheme that aborts the "least important" of the interfering transactions. The second protocol, peep, overrides SCCP by consulting process-specific control rules, written by the project administration. Each control rule describes a specific interference and the actions that resolve it. We have implemented SCCP and parts ofPCCP in MARVEL, a multi-user rule-based SDE developed at Columbia

Consistency and Automation in Multi-User Rule-Based Development Environments

We investigate the scaling up of a class of single-user software development environments, which we call rule-based development environments (RBDEs), to support multiple developers cooperating together on a project. RBDEs model the software development process in terms of rules that encapsulate activities, and execute forward and backward chaining on the rules to provide assistance in carrying out the development process. There is a spectrum of assistance models, ranging from pure automation to strict consistency preservation. We describe three problems whose solutions are dependent on the choice of assistance model: (1) multiple views; (2) evolution; and (3) concurrency control. We discuss how the two extremes of the spectrum restrict the possible approaches to multiple views and evolution. In order to explore different aspects of the concurrency control problem across multiple points on the spectrum of RBDEs, we develop a maximalist assistance model and propose an approach to synchronization of cooperating developers within the context of this model

Concurrency Control in Advanced Database Applications

Concurrency control has been thoroughly studied in the context of traditional database applications such as banking and airline reservations systems. There are relatively few studies, however, that address the concurrency control issues of advanced database applications such as CAD/CAM and software development environments. The concurrency control requirements in such applications are different from those in conventional database applications; in particular, there is a need to support non-serializable cooperation among users whose transactions are long-lived and interactive, and to integrate concurrency control mechanisms with version and configuration control. This paper outlines the characteristics of data and operations in some advanced database applications, discusses their concurrency control requirements, and surveys the mechanisms proposed to address these requirements

Concurrency Control in Advanced Database Applications

Concurrency control has been thoroughly studied in the context of traditional database applications such as banking and airline reservations systems. There are relatively few studies, however, that address the concurrency control issues of advanced database applications such as CAD/CAM and software development environments. The concurrency control requirements in such applications are different from those in conventional database applications; in particular, there is a need to support non-serializable cooperation among users whose transactions are long-lived and interactive, and to integrate concurrency control mechanisms with version and configuration control. This paper outlines the characteristics of data and operations in some advanced database applications, discusses their concurrency control requirements, and surveys the mechanisms proposed to address these requirements

Marvel Implementor's Guide

This document is an implementor's manual for the MARVEL software development environment. It discusses the technical details of the system, rather than providing a description of the system. It is intended for those people doing actual development work on MARVEL. References are provides throughout the manual for background information