\u3cem\u3eRTC\u3c/em\u3e: Language Support for Real-Time Concurrency

This paper presents language constructs for the expression of timing and concurrency requirements in distributed real-time programs. Our programming paradigm combines an object-based paradigm for the specification of shared resources, and a distributed transaction-based paradigm for the specification of application processes. Resources provide abstract views of shared system entities, such as devices and data structures. Each resource has a state and defines a set of actions that can be invoked by processes to examine or change its state. A resource also specifies scheduling constraints on the execution of its actions to ensure the maintenance of its state\u27s consistency. Processes access resources by invoking actions and express precedence, consistency. Processes access resources by invoking actions and express precedence, consistency and timing constraints on action invocations. The implementation of our language constructs with real-time scheduling and locking for concurrency control is also described

Time patterns for process-aware information systems

Companies increasingly adopt process-aware information systems (PAISs) due to their promising perspectives for improved business process support. Although the proper handling of temporal constraints is crucial in this context, existing PAISs vary significantly regarding their support of the temporal perspective of a business process. To make PAISs comparable with respect to their ability to deal with temporal constraints and to facilitate the development of a time-aware PAIS, this paper suggests 10 time patterns. All patterns are based on empirical evidence we gathered in case studies. Additionally, they are validated through a systematic literature review. Based on the time patterns, we then provide an in-depth evaluation of selected PAISs and academic approaches. Altogether, the 10 time patterns will not only facilitate the selection of technologies for realizing time- and process-aware information systems but can also be used as reference for implementing time support in PAISs

RK: A Real-Time Kernel for a Distributed System With Predictable Response

Robotics applications must execute in real-time. In addition, complex robotics applications include many physically distributed components such as manipulator arms and sensors. This paper presents the real-time kernel RK which is designed to facilitate the development of a distributed sensory system with multiple arms and sensors. The goal of the kernel is to support distributed applications that require predictable timing behavior. Our kernel design guarantees predictable response times by scheduling processes and communications based on timing constraints. In addition, the kernel provides a set of primitives that can be used to implement applications requiring predictable timing behavior. These primitives allow the specification of timing requirements that can be guaranteed in advance by the scheduler and the direct control of devices by application processes for faster and predictable feedback control. To illustrate the use of our kernel, this paper also describes a multiple sensory system which is being ported to our distributed test-bed

Project scheduling under undertainty – survey and research potentials.

The vast majority of the research efforts in project scheduling assume complete information about the scheduling problem to be solved and a static deterministic environment within which the pre-computed baseline schedule will be executed. However, in the real world, project activities are subject to considerable uncertainty, that is gradually resolved during project execution. In this survey we review the fundamental approaches for scheduling under uncertainty: reactive scheduling, stochastic project scheduling, stochastic GERT network scheduling, fuzzy project scheduling, robust (proactive) scheduling and sensitivity analysis. We discuss the potentials of these approaches for scheduling projects under uncertainty.Management; Project management; Robustness; Scheduling; Stability;

Synthesising robust schedules for minimum disruption repair using linear programming

An off-line scheduling algorithm considers resource, precedence, and synchronisation requirements of a task graph, and generates a schedule guaranteeing its timing requirements. This schedule must, however, be executed in a dynamic and unpredictable operating environment where resources may fail and tasks may execute longer than expected. To accommodate such execution uncertainties, this paper addresses the synthesis of robust task schedules using a slack-based approach and proposes a solution using integer linear programming (ILP). Earlier we formulated a time slot based ILP model whose solutions maximise the temporal flexibility of the overall task schedule. In this paper, we propose an improved, interval based model, compare it to the former, and evaluate both on a set of random scenarios using two public domain ILP solvers and a proprietary SAT/ILP mixed solver

A survey of variants and extensions of the resource-constrained project scheduling problem

The resource-constrained project scheduling problem (RCPSP) consists of activities that must be scheduled subject to precedence and resource constraints such that the makespan is minimized. It has become a well-known standard problem in the context of project scheduling which has attracted numerous researchers who developed both exact and heuristic scheduling procedures. However, it is a rather basic model with assumptions that are too restrictive for many practical applications. Consequently, various extensions of the basic RCPSP have been developed. This paper gives an overview over these extensions. The extensions are classified according to the structure of the RCPSP. We summarize generalizations of the activity concept, of the precedence relations and of the resource constraints. Alternative objectives and approaches for scheduling multiple projects are discussed as well. In addition to popular variants and extensions such as multiple modes, minimal and maximal time lags, and net present value-based objectives, the paper also provides a survey of many less known concepts. --project scheduling,modeling,resource constraints,temporal constraints,networks