William R. Otte

DAnCE: a qos-enabled component deployment and configuration engine

This paper presents two contributions to the study of component deployment for distributed real-time and embedded (DRE) systems. First, it uses an inventory tracking systems (ITS) as a case study to elicit challenges involved in deploying DRE systems to account for their quality of service requirements. Second, it describes how we designed and implemented the Deployment And Configuration Engine (DAnCE), which is QoS-enabled middleware that addresses the challenges that arose in the context of our ITS case study. Our experience shows that DAnCE provides an effective platform for deploying DRE system components using a standard runtime environment and metadata.

A software platform for fractionated spacecraft

A fractionated spacecraft is a cluster of independent modules that interact wirelessly to maintain cluster flight and realize the functions usually performed by a monolithic satellite. This spacecraft architecture poses novel software challenges because the hardware platform is inherently distributed, with highly fluctuating connectivity among the modules. It is critical for mission success to support autonomous fault management and to satisfy real-time performance requirements. It is also both critical and challenging to support multiple organizations and users whose diverse software applications have changing demands for computational and communication resources, while operating on different levels and in separate domains of security. The solution proposed in this paper is based on a layered architecture consisting of a novel operating system, a middleware layer, and component-structured applications. The operating system provides primitives for concurrency, synchronization, and secure information flows; it also enforces application separation and resource management policies. The middleware provides higher-level services supporting request/response and publish/subscribe interactions for distributed software. The component model facilitates the creation of software applications from modular and reusable components that are deployed in the distributed system and interact only through well-defined mechanisms. Two cross-cutting aspects - multi-level security and multi-layered fault management - are addressed at all levels of the architecture. The complexity of creating applications and performing system integration is mitigated through the use of a domain-specific model-driven development process that relies on a dedicated modeling language and its accompanying graphical modeling tools, software generators for synthesizing infrastructure code, and the extensive use of model-based analysis for verification and validation.

The design and performance of component middleware for QoS-enabled deployment and configuration of DRE systems

Quality of Service (QoS)-enabled component middleware can help reduce the complexity of deploying and configuring QoS aspects, such as priorities and rates of invocation. Few empirical studies have been conducted, however, to guide developers of distributed real-time and embedded (DRE) systems in choosing among alternative designs and performance optimizations. Moreover, few empirical studies have been conducted to examine the performance and flexibility trade-offs between standards-based and domain-specific DRE middleware solutions. This paper makes three key contributions to research on QoS-enabled component middleware for DRE systems. First, it describes optimizations applied to an implementation of the OMGs Deployment and Configuration (D&C) of Components specification that enable performance trade-offs between QoS aspects of DRE systems. Second, it compares the performance of several dynamic and static configuration mechanisms to help guide the selection of suitable configuration mechanisms based on specific DRE system requirements. Third, it compares the performance of our static standards-based approach to an avionics domain-specific approach. Our results show that these optimizations (1) provide developers improved control over key trade-offs between flexibility and performance at different stages of the DRE system lifecycle, (2) enhance trustworthiness of component-based DRE systems by supporting greater customization of how they are configured to meet specific requirements of each application, and (3) offer greater flexibility at a reasonable performance cost, compared to a domain-specific approach.

A Multi-Agent Architecture Provides Smart Sensing for the NASA Sensor Web

Remote sensing missions for Earth Science contribute greatly to the understanding of the dynamics of our planet. Conventional approaches however, impede the scientific communitys ability to (1) generate and refine models of complex phenomena, such as, extended weather forecasting, (2) detect and rapidly respond to critical transient events (e.g., disasters, such as hurricanes and floods). This paper describes a more effective approach based on intelligent, networked sensor webs that incorporate seamless dynamic connectivity between spacecraft, aircraft, and in situ terrestrial sensors, employs reactive and proactive strategies for improved temporal, spectral, and spatial coverage of the earth and its atmosphere, and uses enhanced dynamic decision-making for rapid responses to changing situations. MACRO, an extension of our earlier work on a multi-agent framework for heterogeneous spacecraft constellations, will provide interoperability and autonomy to achieve the needs for smart sensing in NASAs proposed sensor web. The system capability will be demonstrated via a simulated but salient disaster management scenario on an existing hardware testbed at the Lockheed Martin Advanced Technology Center.

Efficient and deterministic application deployment in component-based enterprise distributed real-time and embedded systems

Context: Component-based middleware, such as the Lightweight CORBA Component Model, is increasingly used to implement enterprise distributed real-time and embedded (DRE) systems. In addition to supporting the quality-of-service (QoS) requirements of individual DRE systems, component technologies must also support bounded latencies when effecting deployment changes to DRE systems in response to changing environmental conditions and operational requirements. Objective: The goals of this paper are to (1) study sources of inefficiencies and non-deterministic performance in deployment capabilities for DRE systems and (2) devise solutions to overcome these performance problems. Method: The paper makes two contributions to the study of the deployment and configuration of distributed component based applications. First, we analyze how conventional implementations of the OMGs Deployment and Configuration (D&C) specification for component-based systems can significantly degrade deployment latencies. Second, we describe architectural changes and performance optimizations implemented within the Locality-Enhanced Deployment and Configuration Engine (LE-DAnCE) implementation of the D&C specification to obtain efficient and deterministic deployment latencies. Results: We analyze the performance of LE-DAnCE in the context of component deployments on 10 nodes for a representative DRE system consisting of 1000 components and in a cluster environment with up to 100 nodes. Our results show LE-DAnCEs optimizations provide a bounded deployment latency of less than 2s for the 1000 component scenario with just a 4 percent jitter. Conclusion: The improvements contained in the LE-DAnCE infrastructure provide an efficient and scaleable standards-based deployment system for component-based enterprise DRE systems. In particular, deployment time parallelism can improve deployment latency significantly, both during pre-deployment analysis of the deployment plan and during the process of installing and activating components.

Predictable deployment in component-based enterprise distributed real-time and embedded systems

Component-based middleware, such as the Lightweight CORBA Component Model, are increasingly used to implement large-scale distributed real-time and embedded (DRE) systems. In addition to supporting the quality of service (QoS) requirements of individual DRE systems, component technologies must also support bounded latencies when effecting deployment changes to DRE systems in response to changing environmental conditions and operational requirements. This paper makes three contributions to the study of predictable deployment latencies in DRE systems. First, we describe OMGs Deployment and Configuration (D&C) specification for component-based systems and discuss how conventional implementations of this standard can significantly degrade deployment latencies. Second, we describe architectural changes and performance optimizations implemented within the Locality-Enhanced Deployment and Configuration Engine (LE-DAnCE) implementation of the D&C specification. Finally, we analyze the performance of LE-DAnCE in the context of component deployments on 10 nodes for a representative DRE system consisting of 1,000 components. Our results show LE-DAnCEs optimizations provide a bounded deployment latency of less than 2 seconds with 2 percent jitter.

Achieving resilience in distributed software systems via self-reconfiguration

We describe resilient operation of cyber-physical application platforms.We describe implicit design-time encoding of the reconfiguration.We describe design-time analysis and validation tools for these systems. Improvements in mobile networking combined with the ubiquitous availability and adoption of low-cost development boards have enabled the vision of mobile platforms of Cyber-Physical Systems (CPS), such as fractionated spacecraft and UAV swarms. Computation and communication resources, sensors, and actuators that are shared among different applications characterize these systems. The cyber-physical nature of these systems means that physical environments can affect both the resource availability and software applications that depend on resource availability. While many application development and management challenges associated with such systems have been described in existing literature, resilient operation and execution have received less attention. This paper describes our work on improving runtime support for resilience in mobile CPS, with a special focus on our runtime infrastructure that provides autonomous resilience via self-reconfiguration. We also describe the interplay between this runtime infrastructure and our design-time tools, as the later is used to statically determine the resilience properties of the former. Finally, we present a use case study to demonstrate and evaluate our design-time resilience analysis and runtime self-reconfiguration infrastructure.

Intelligent Resource Management and Dynamic Adaptation in a Distributed Real-time and Embedded Sensor Web System

Sensor webs are often composed of servers connected to distributed real-time embedded (DRE) systems that operate in open environments where operating conditions, workload, resource availability, and connectivity cannot be accurately characterized a priori. The South East Alaska MOnitoring Network for Science, Telecommunications, Education, and Research (SEAMONSTER) project exhibits many common system management and dynamic operation challenges for effective, autonomous system adaptation in a representative sensor web. These challenges cover both field operation ({\em e.g.}, power management through system sleep/wake cycles and reaction to local environmental changes) and server operation ({\em e.g.}, system adaptation for new/modified goals, resource allocation for a changing set of applications, and configuration changes for fluctuating workload). This paper presents the results of integrating and applying quality-of-service (QoS)-enabled component middleware, dynamic resource management, and autonomous agent technologies to address these challenges in SEAMONSTER.

Real-time fault tolerant deployment and configuration framework for cyber physical systems

This paper describes ongoing work on making the deployment and configuration functionality for cyber physical systems reliable and tolerant to failures, while also supporting predictable and incremental online redeployment and reconfiguration of application functionality. Our work is currently designed and evaluated in the context of a system of fractionated spacecrafts, which is a representative CPS system.

A flexible infrastructure for distributed deployment in adaptive sensor webs

Distributed sensor webs typically operate in dynamic environments where operating conditions, transient phenomena, availability of resources, and network connection quality change frequently and unpredictably. Often these changes can neither be completely anticipated nor accurately described during development or deployment. Our prior work has described how we developed agents and services that are capable of monitoring these changing conditions and adapting system parameters using the CORBA Component Model (CCM) deployment infrastructure as part of the Multiagent Architecture for Coordinated Responsive Observations (MACRO) platform. Our recent application of MACRO to the South East Alaska MOnitoring Network for Science, Telecommunications, Education, and Research (SEAMONSTER) project has identified new distributed deployment infrastructure challenges common to computationally constrained field environments in adaptive sensor webs. These challenges include standardized execution of low-level hardware-dependent actions and on-going data tasks, automated provisioning of agents for heterogeneous field hardware, and minimizing deployment infrastructure overhead. This paper describes how we extended MACRO to address these sensor web challenges by creating an action/effector framework standardizing the execution of lightweight actions and providing for automated provisioning of MACRO agents, in addition to footprint optimizations to the underlying CCM infrastructure.