Gan Deng

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.

Model driven middleware: A new paradigm for developing distributed real-time and embedded systems

Distributed real-time and embedded (DRE) systems have become critical in domains such as avionics (e.g., flight mission computers), telecommunications (e.g., wireless phone services), tele-medicine (e.g., robotic surgery), and defense applications (e.g., total ship computing environments). These types of system are increasingly interconnected via wireless and wireline networks to form systems of systems. A challenging requirement for these DRE systems involves supporting a diverse set of quality of service (QoS) properties, such as predictable latency/jitter, throughput guarantees, scalability, 24x7 availability, dependability, and security that must be satisfied simultaneously in real-time. Although increasing portions of DRE systems are based on QoS-enabled commercial-off-the-shelf (COTS) hardware and software components, the complexity of managing long lifecycles (often ~15-30 years) remains a key challenge for DRE developers and system integrators. For example, substantial time and effort is spent retrofitting DRE applications when the underlying COTS technology infrastructure changes. This paper provides two contributions that help improve the development, validation, and integration of DRE systems throughout their lifecycles. First, we illustrate the challenges in creating and deploying QoS-enabled component middleware-based DRE applications and describe our approach to resolving these challenges based on a new software paradigm called Model Driven Middleware (MDM), which combines model-based software development techniques with QoS-enabled component middleware to address key challenges faced by developers of DRE systems - particularly composition, integration, and assured QoS for end-to-end operations. Second, we describe the structure and functionality of CoSMIC (Component Synthesis using Model Integrated Computing), which is an MDM toolsuite that addresses key DRE application and middleware lifecycle challenges, including partitioning the components to use distributed resources effectively, validating software configurations, assuring multiple simultaneous QoS properties in real-time, and safeguarding against rapidly changing technology.

Model-Driven Configuration and Deployment of Component Middleware Publish/Subscribe Services

Quality of service (QoS)-enabled publish/subscribe services are available in component middleware platforms, such as the CORBA Component Model (CCM). Today, however, these platforms lack a simple and intuitive way to integrate publish/subscribe service configurations and deployments. This paper illustrates how generative model-driven techniques and tools can automate many service configuration and deployment tasks associated with integrating publish/subscribe services into QoS-enabled component-based systems. We evaluatethese techniques in the context of a real-time avionics mission computing problem involving a system with over 50 components. Our evaluation finds that an automated model-driven configuration of a reusable component middleware framework not only significantly reduces handwritten code and but also simultaneously achieves high reusability and composability of CCM components.

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.

Evaluating Real-Time Publish/Subscribe Service Integration Approaches in QoS-Enabled Component Middleware

As quality of service (QoS)-enabled component middleware technologies gain widespread acceptance to build distributed real-time and embedded (DRE) systems, it becomes necessary for these technologies to support real-time publish/subscribe services, which is a key requirement of a large class of DRE systems. To date there have been very limited systematic studies evaluating different approaches to integrating real-time publish/subscribe services in QoS-enabled component middleware. This paper makes two contributions in addressing these key research questions. First, we evaluate the pros and cons of three different design alternatives for integrating publish/subscribe services within QoS-enabled component middleware. Second, we empirically evaluate the performance of our container-based design and compare it with mature object-oriented real-time publish/subscribe implementations. Our studies reveal that both the performance and scalability of our design and implementation are comparable to its object-oriented counterpart, which provides a key guidance to the suitability of component technologies for DRE systems.

Addressing domain evolution challenges in software product lines

It is hard to develop and evolve software product-line architectures (PLAs) for large-scale distributed real-time and embedded (DRE) systems. Although certain challenges of PLAs can be addressed by combining model-driven development (MDD) techniques with component frameworks, domain evolution problems remain largely unresolved. In particular, extending or refactoring existing software product-lines to handle unanticipated requirements or better satisfy current requirements requires significant effort. This paper describes techniques for minimizing such impacts on MDD-based PLAs for DRE systems through a case study that shows how a layered architecture and model-to-model transformation tool support can re duce the effort of PLA evolution.

Middleware support for dynamic component updating

Component technologies are increasingly being used to develop and deploy distributed real-time and embedded (DRE) systems. To enhance flexibility and performance, developers of DRE systems need middleware mechanisms that decouple component logic from the binding of a component to an application, i.e., they need support for dynamic updating of component implementations in response to changing modes and operational contexts. This paper presents three contributions to R&D on dynamic component updating. First, it describes an inventory tracking system (ITS) as a representative DRE system case study to motivate the challenges and requirements of updating component implementations dynamically. Second, it describes how our SwapCIAO middleware supports dynamic updating of component implementations via extensions to the server portion of the Lightweight CORBA Component Model. Third, it presents the results of experiments that systematically evaluate the performance of SwapCIAO in the context of our ITS case study. Our results show that SwapCIAO improves the flexibility and performance of DRE systems, without affecting the client programming model or client/server interoperability.

Addressing crosscutting deployment and configuration concerns of distributed real-time and embedded systems via aspect-oriented & model-driven software development

Model-driven development (MDD) is gaining importance as an approach to resolving lifecycle challenges of large-scale distributed real-time and embedded (DRE) systems (e.g., avionics mission computing). DRE systems are characterized by their stringent requirements for quality of service (QoS), such as predictable end-to-end latencies, timeliness and scalability. Delivering the QoS needs of DRE systems entails the need to configure correctly, fine tune and provision the infrastructure used to host the DRE systems, which crosscuts different layers of middleware, operating systems and networks. Addressing these tangled deployment and configuration concerns of DRE systems requires integrating the principles of Aspect-Oriented Software Development (AOSD) with MDD. This demo showcases a set of software tools that resolve both the inherently and accidental complexities arising due to the configuration and deployment crosscutting concerns of component middleware-based DRE systems.

CaDAnCE: A Criticality-Aware Deployment and Configuration Engine

Predictable deployment and configuration (D&C) of components in response to dynamic environmental changes or system mode changes is essential for ensuring open distributed real-time and embedded (DRE) system real-time QoS. This paper provides three contributions to research on the predictability of D&C for component-based open DRE systems. First, we describe how the dependency relationships among different components and their criticality levels can cause deployment order inversion of tasks, which impedes deployment predictability. Second, we describe how to minimize D&C latency of mission-critical tasks with a multi-graph dependency tracing and graph recomposition algorithm called CaDAnCE. Third, we empirically evaluate the effectiveness of CaDAnCE on a representative open DRE system case study based on NASA Earth Science Enterprises Magnetospheric Multi-Scale (MMS) mission system. Our results show that CaDAnCE avoids deployment order inversion while incurring negligible (<1%) performance overhead, thereby significantly improving D&C predictability.

Model-driven integration of federated event services in real-time component middleware

Rapid advances in hardware, networking technologies and software technologies, including standards-based optimized component middleware, has enabled the growth of component middleware-based complex, large-scale distributed real-time and embedded (DRE) systems. These DRE systems found in different domains, such as avionics, telecommunications, defense, enterprise and healthcare, often use a publisher/subscriber communication paradigm, such as that provided by an event service. A federation of such event services provides a scalable solution to address the complex distribution challenges of DRE systems. By connecting event channels from different systems together a federated event service enables seamless and application-transparent interchange of event information across distribution boundaries.Although component middleware supports the creation of applications via composition of reusable and flexible software components, however, to deploy such systems effectively involves numerous challenges in integrating the various distributed components communicating via different event channels. Current state of the art in deploying a federation of event services for these component middleware-based DRE systems involves ad hoc techniques that are tedious and error-prone.This paper describes a novel scheme we have developed based on a model-based paradigm that resolves the challenges in configuring the federated event service. Our approach centers around the notion of the federated event service modeling language (FESML), which is a modeling tool we have developed to resolve the configuration and deployment challenges of federated event service for component middleware-based DRE systems.