Seyed Masoud Sadjadi

Composing adaptive software

Interest in adaptive computing systems has increased dramatically in the past few years, and a variety of techniques now allow software to adapt dynamically to its environment. Compositional adaptation enables software to modify its structure and behavior dynamically in response to change in its execution environment. A review of current technology compares how, when, and where recomposition occurs.

An aspect-oriented approach to dynamic adaptation

This paper presents an aspect-oriented approach to dynamic adaptation. A systematic process for defining where, when, and how an adaptation is to be incorporated into an application is presented. Specifically, the paper presents a two-phase approach to dynamic adaptation, where the first phase prepares a non-adaptive program for adaptation, and the second phase implements the adaptation at run time. This approach is illustrated with a distributed conferencing application.

ACT: an adaptive CORBA template to support unanticipated adaptation

We propose an Adaptive CORBA Template (ACT), which enables run-time improvements to CORBA applications in response to unanticipated changes in either their functional requirements or their execution environments. ACT enhances CORBA applications by transparently weaving adaptive code into their object request brokers (ORBs) at run time. The woven code intercepts and adapts the requests, replies, and exceptions that pass through the ORBs. Specifically, ACT can be used to develop an object-oriented framework in any language that supports dynamic loading of code and can be applied to any CORBA ORB that supports portable interceptors. Moreover, ACT can be used to support interoperation among otherwise incompatible adaptive CORBA frameworks. To evaluate the performance and functionality of ACT, we implemented a prototype in Java. Our experimental results show that the overhead introduced by the ACT infrastructure is negligible, while the adaptations offered are highly flexible.

An Analysis of Provisioning and Allocation Policies for Infrastructure-as-a-Service Clouds

Today, many commercial and private cloud computing providers offer resources for leasing under the infrastructure as a service (IaaS) paradigm. Although an abundance of mechanisms already facilitate the lease and use of single infrastructure resources, to complete multi-job workloads IaaS users still need to select adequate provisioning and allocation policies to instantiate resources and map computational jobs to them. While such policies have been studied in the past, no experimental investigation in the context of clouds currently exists that considers them jointly. In this paper we present a comprehensive and empirical performance-cost analysis of provisioning and allocation policies in IaaS clouds. We first introduce a taxonomy of both types of policies, based on the type of information used in the decision process, and map to this taxonomy eight provisioning and four allocation policies. Then, we analyze the performance and cost of these policies through experimentation in three clouds, including Amazon EC2. We show that policies that dynamically provision and/or allocate resources can achieve better performance and cost. Finally, we also look at the interplay between provisioning and allocation, for which we show preliminary results.

Architecture and operation of an adaptable communication substrate

This paper describes the internal architecture and operation of an adaptable communication component called the MetaSocket. MetaSockets are created using Adaptive Java, a reflective extension to Java that enables a components internal architecture and behavior to be adapted at run time in response to external stimuli. This paper describes how adaptive behavior is implemented in MetaSockets, as well as how MetaSockets interact with other adaptive components, such as decision makers and event mediators. Results of experiments on a mobile computing testbed demonstrate how MetaSockets respond to dynamic wireless channel conditions in order to improve the quality of interactive audio streams delivered to iPAQ handheld computers.

Enabling Interoperability among Meta-Schedulers

Grid computing supports shared access to computing resources from cooperating organizations or institutes in the form of virtual organizations. Resource brokering middleware, commonly known as a meta-scheduler or a resource broker, matches jobs to distributed resources. Recent advances in meta- scheduling capabilities are extended to enable resource matching across multiple virtual organizations. Several architectures have been proposed for interoperating meta-scheduling systems. This paper presents a hybrid approach, combining hierarchical and peer-to-peer architectures for flexibility and extensibility of these systems. A set of protocols are introduced to allow different meta-scheduler instances to communicate over Web Services. Interoperability between three heterogeneous and distributed organizations (namely, BSC, FIU, and IBM), each using different meta-scheduling technologies, is demonstrated under these protocols and resource models.

Looking for an Evolution of Grid Scheduling: Meta-Brokering

A Grid Resource Broker for a Grid domain, or also known as meta-scheduler, is a middleware component used for matching works to available Grid resources from one or more IT organizations. A Grid meta-scheduler usually has its own interfaces for the functionalities it provides and its own job scheduling objectives. This situation causes two main problems: the user uniform access to the Grid is lost, and the scheduling decisions are taken separately while they should be done in coordination. These problems have been observed in different efforts such as the HPC-Europa project but they are still open problems. In this paper we discuss the requirements to achieve a more uniform access to the Grids through a new approach to global brokering. As the results of these discussions on brokering requirements, we propose a meta-brokering design, so called metameta-scheduler design, and discuss how it can be realized as a centralized model for the HPC-Europa project, and as a distributed model for the LA Grid project.

Service Clouds: Distributed Infrastructure for Adaptive Communication Services

This paper describes service clouds, a distributed infrastructure designed to facilitate rapid prototyping and deployment of adaptive communication services. The infrastructure combines adaptive middleware functionality with an overlay network substrate in order to support dynamic instantiation and reconfiguration of services. The service clouds architecture includes a collection of low-level facilities that can be invoked directly by applications or used to compose more complex services. After describing the service clouds architecture, we present results of experimental case studies conducted on the PlanetLab Internet testbed alone and a mobile computing testbed.

Transparent self-optimization in existing CORBA applications

This paper addresses the design of adaptive middleware to support autonomic computing in pervasive computing environments. The particular problem we address here is how to support self-optimization to changing network connection capabilities as a mobile user interacts with heterogeneous elements in a wireless network infrastructure. The goal is to enable self-optimization to such changes transparently with respect to the core application code. We propose a solution based on the use of the generic proxy, which is a specific CORBA object that can intercept and process any CORBA request using rules and actions that can be introduced to the knowledge base of the proxy during execution. To explore its design and operation, we have incorporated the generic proxy into ACT (Sadjadi and McKinley, 2004), an adaptive middleware framework we designed previously to support adaptation in CORBA applications. Details of the generic proxy are presented. A case study is described in which a generic proxy is used to support self-optimization in an existing image retrieval application, when executed in a heterogeneous wireless environment.

A Communication Virtual Machine

The convergence of data, voice and multimedia communication over digital networks, coupled with continuous improvement in network capacity and reliability has significantly enriched the ways we communicate. However, the stovepipe approach used to develop todays communication applications and tools results in rigid technology, limited utility, lengthy and costly development cycle, difficulty in integration, and hinders innovation. In this paper, we present a fundamentally different approach, which we call communication virtual machine (CVM) to address these problems. CVM provides a user-centric, model-driven approach for conceiving, synthesizing and delivering communication solutions across application domains. We argue that CVM represents a far more effective paradigm for engineering communication solutions. The concept, architecture, modeling language, prototypical design and implementation of CVM are discussed