Amogh Kavimandan

Applying Model Transformations to Optimizing Real-Time QoS Configurations in DRE Systems

The quality of a software architecture for component-based distributed systems is defined not just by its source code but also by other systemic artifacts, such as the assembly, deployment, and configuration of the application components and their component middleware. In the context of distributed, real-time, and embedded (DRE) component-based systems, bin packing algorithms and schedulability analysis have been used to make deployment and configuration decisions. However, these algorithms make only coarse-grained node assignments but do not indicate how components are allocated to different middleware containers on the node, which are known to impact runtime system performance and resource consumption. This paper presents a model transformation-based algorithm that combines user-specified quality of service (QoS) requirements with the node assignments to provide a finer level of granularity and precision in the deployment and configuration decisions. A beneficial side effect of our work lies in how these decisions can be leveraged by additional backend performance optimization techniques. We evaluate our approach and compare it against the existing state-of-the-art in the context of a representative DRE system.

Automated Middleware QoS Configuration Techniques for Distributed Real-time and Embedded Systems

Quite often the modeling tools used in the development lifecycle of distributed real-time and embedded (DRE) systems are middleware-specific, where they elevate middleware artifacts, such as configuration options, to first class modeling entities. Unfortunately, this level of abstraction does not resolve the complex issues in middleware configuration process for QoS assurance. This paper describes GT-QMAP (graph transformation for QoS mapping) model-driven engineering toolchain that combines (1) domain-specific modeling, to simplify specifying the QoS requirements of DRE systems intuitively, and (2) model transformations, to automate the mapping of domain-specific QoS requirements to middleware-specific QoS configuration options. The paper evaluates the automation capabilities of GT-QMAP in the context of three DRE system case studies. The results indicate that on an average the modeling effort is reduced by over 75%. Further, the results also indicate that GT-QMAP provides significant benefits in terms of scalability and automation as DRE system QoS requirements evolve during its entire development lifecycle.

Automated Middleware QoS Configuration Techniques using Model Transformations

This paper provides following three contributions to the study of developing and applying model driven engineering (MDE) techniques to quality of service (QoS) configuration of distributed real-time and embedded (DRE) systems. First, we describe the challenges associated with mapping domain-level QoS policies of DRE systems to middleware configuration space. Second, we discuss a domain specific modeling language (DSML) to capture QoS requirements of DRE system at a higher level of abstraction, simplifying the system QoS specification process. Third, we describe model transformations to automate the mapping of domain-specific QoS requirements.Our results indicate that our approach provides significant benefits in terms of productivity, scalability, reusability and automation of middleware QoS mapping compared to traditional QoS configuration techniques for publish/subscribe-based DRE systems.

Network simulation via hybrid system modeling: a time-stepped approach

The ever increasing complexity of networks dramatically increases the challenges faced by service providers to analyze network behavior and (re)provision resources to support multiple complex distributed applications. Accurate and scalable simulation tools are pivotal to this cause. The recently proposed hybrid systems model for data communication networks shows promise in achieving performance characteristics comparable to fluid models while retaining the accuracy of discrete models. Using the hybrid systems paradigm, this paper provides contributions to the modeling of TCP behavior and the analysis/simulation of data communication networks based on these models. An important distinguishing feature of our simulation framework is a faithful accounting of link propagation delays which has been ignored in previous work for the sake of simplicity. Other salient aspects of the work include a new finite state machine model for a drop-tail queue, a new model for fast recovery/fast retransmit mode, a revised sending rate model, and an embedded time-out mode transition mechanism all of which employ a time-stepped solution method to solve the hybrid system network models. Our simulation results are consistent with well-known packet based simulators such as ns-2, thus demonstrating the accuracy of our hybrid model. Our future efforts will be directed towards studying and improving the computational performance of hybrid model based simulations.

Managing the quality of software product line architectures through reusable model transformations

In model-driven engineering of applications, the quality of the software architecture is realized and preserved in the successive stages of its lifecycle through model transformations. However, limited support for reuse in contemporary model transformation techniques forces developers of product line architectures to reinvent transformation rules for every variant of the product line, which can adversely impact developer productivity and in turn degrade the quality of the resulting software architecture for the variant. To overcome these challenges, this paper presents the MTS (Model-transformation Templatization and Specialization generative transformation process, which promotes reuse in model transformations through parameterization and specialization of transformation rules. MTS defines two higher order transformations to capture the variability in transformation rules and to specialize them across product variants. The core idea behind MTS is realized within a graphical model transformation tool in a way that is minimally intrusive to the underlying tools implementation. The paper uses two product line case studies to evaluate MTS in terms of reduction in efforts to define model transformation rules as new variants are added to the product line, and the overhead in executing the higher order transformations. These metrics provide an indirect measure of how potential degradation in the quality of software architectures of product lines caused due to lack of reuse can be alleviated by MTS.

A parameterized model transformations approach for automating middleware QoS configurations in distributed real-time and embedded systems

Model transformation is a key requirement of model-based software development processes, such as middleware quality of service (QoS) configuration which involves mapping domain-specific requirements onto the right set of middleware-specific configuration options. There exists a significant opportunity to factor out commonality patterns from individual platform-specific transformation mappings to develop general-purpose transformations. Although existing model transformation tools provide support for developing, testing and debugging transformation rules using a variety of approaches, the development of templatized, reusable (patterns of) model transformations is not well supported. We introduce the concept of transformation template specialization that:(1) allows developers to specify variability points in their transformation project, (2) automatically creates a modeling language that captures middleware platform variabilities, and (3) accommodates these varabilities in the transformation project such that platform-specific model transformations can be instantiated.

Towards a QoS Modeling and Modularization Framework for Component-based Systems

Current domain-specific modeling (DSM) frameworks for designing component-based systems provide modeling support for systems structural as well as non-functional or quality of service (QoS) concerns. However, the focus of such frameworks on systems non-functional concerns is an after-thought and their support is at best adhoc. Further, such frameworks lack strong decoupling between the modeling of the systems structural composition and their QoS requirements. This lack of QoS modularization limits (1) reusability of such frameworks, (2) ease of their maintenance when new non-functional characteristics are added, and (3) independent evolution of the modeling frameworks along both the structural and non-functional dimensions. This paper describes Component QoS modeling language (CQML), which is a reusable, extensible, and platform-independent QoS Modeling Language that provides strong separation between the structural and non-functional dimensions. CQML supports independent evolution of structural metamodel of composition modeling languages as well as QoS metamodel. To evaluate, we superimpose CQML on a purely structural modeling language and automatically generate, configure, and deploy componentbased fault-monitoring infrastructure using aspect-oriented modeling (AOM) techniques.

QUICKER: A Model-Driven QoS Mapping Tool for QoS-Enabled Component Middleware

This paper provides three contributions to the study of quality of service (QoS) configuration in component-based DRE systems. First, we describe the challenges associated with mapping the platform-independent QoS policies of an application into platform-dependent values of QoS parameters used to configure the behavior of QoS-enabled component middleware. Second, we describe a novel approach that uses model-transformation to map these QoS policies onto component middleware QoS configuration parameters. Third, we demonstrate the use of model-checking to verify the properties of the transformation and automate the synthesis of configuration parameters required to tune the QoS-enabled component middleware. Our results indicate that model-transformation and model-checking provide significant benefits with respect to automation, reusability, verifiability, and scalability of the QoS mapping process compared with conventional middleware configuration techniques

Evaluating the Correctness and Effectiveness of a Middleware QoS Configuration Process in Distributed Real-Time and Embedded Systems

Recent advances in software processes and artifacts for automating middleware configurations in distributed realtime and embedded (DRE) systems are starting to address the complexities faced by system developers in dealing with the flexibility and configurability provided by contemporary middleware. Despite the benefits of these new processes, there remain significant challenges in verifying their correctness, and validating their effectiveness in meeting the end-to-end quality of service (QoS) requirements of DRE systems. This paper addresses this problem by describing how model-checking and structural correspondence can be used to verify the correctness of a middleware QoS configuration process that uses model-based graph transformations at its core. Next, it provides empirical proof to validate the effectiveness of our technique to meet the end-to-end QoS requirements in the context of a representative DRE system.

Enhancing Enterprise User Productivity with Embedded Context-Aware Voice Applications

The increasing amount of software and computational capabilities in voice endpoints, switches, and networks creates an opportunity for embedding advanced applications in voice communication paths. Particularly in an enterprise environment, such applications can alter the traditional behavior of voice communications from simply connecting two or more people to software-assisted connection establishment and enhanced on-call features. In this paper, we claim that embedding context-aware applications in communication paths can greatly increase the efficiency, effectiveness, and convenience of enterprise communications and thus the productivity of enterprise users. We identify the challenges associated with embedding context-aware applications in communication paths and exemplify our central claim by presenting a context-aware voice communications application CallerID++. CallerID++ aims at improving the aged concept of caller ID as the basis for a callee s decision to accept or reject an incoming call. Through a call acceptance negotiation between caller and callee prior to call establishment, CallerID++ allows the callee to assess the importance of an incoming call relative to the callees current activity. CallerID++ thus helps minimizing unwanted interruptions without rejecting important calls.