Katia Leal

A decentralized model for scheduling independent tasks in Federated Grids

In this paper we present a decentralized model for scheduling independent tasks in Federated Grids. This model consists of a set of meta-schedulers on each of the grid infrastructures of the Federated Grid. Each meta-scheduler has to implement a mapping strategy in order to improve two of the most common objective functions of task scheduling problems: makespan and resource performance. We consider four possible algorithms that have to provide a simple, decoupled, and coarse-grained solution that could be deployed in any Grid. The main axis of the algorithms is that they consider the performance of the infrastructures forming the Federated Grid, not only their state.

A Grid Infrastructure for Utility Computing

Utility computing is a service provisioning model, which provides adaptive, flexible and simple access to computing resources, enabling a pay-per-use model for computing similar to traditional utilities such as water or electricity. The deployment of a utility computing solution involves a full separation between the provider and the consumer. The consumer requires a uniform, secure and reliable functionality to access the utility computing service and the provider requires a scalable, flexible and adaptive infrastructure to provide the service. The solution should be based on standards and allow a gradual deployment in order to obtain a favourable response from the application developers and the information technology staff. Grid technology overcomes such challenges by means of its standard functionality for flexible integration of diverse distributed resources. This position paper proposes an innovative solution for utility computing which can be deployed on a grid infrastructure based on Globus toolkit and GridWay components

Plan B: an operating system for ubiquitous computing environments

The conventional approach for building pervasive environments relies on middleware to integrate different systems. Instead, we have built a system that can deal with these environments by exporting system resources through distributed virtual file systems. This requires no middleware, simplifies interoperation, and permits applying general purpose tools to any system resource. A constraint-based file system import mechanism allows the system to adapt to changes in the environment and permits users to customize the environment and tailor adaptation according to their needs. The system has been in use for over a year to carry out our daily work and is underlying the smart space that we built for our department

Plan B: Using Files instead of Middleware Abstractions

Plan B maps abstract interfaces to files and adapts to file tree availability. It is easy to program, offers a general-purpose computing environment, and supports smart spaces without using middleware.

Traditional Systems Can Work Well for Pervasive Applications. A Case Study: Plan 9 from Bell Labs Becomes Ubiquitous

There is a huge effort in ongoing research on new middleware platforms and new distributed services to support ubiquitous environments and pervasive applications. Prototypes for smart spaces are sometimes used to demonstrate the need for a new particular service, piece of software, or middleware layer. However, we have found that we could easily build a smart space and some applications for it by relying on services already provided by the system we use daily, Plan 9 from Bell Labs. This paper explores how far can we go with a traditional system to support a ubiquitous environment, without using any middleware. We describe how to build a pervasive computing platform using Plan 9, and how we built a smart space to demonstrate this

Omero: ubiquitous user interfaces in the plan B operating system

It is difficult to build user interfaces that must be distributed over a set of dynamic and heterogeneous I/O devices. This difficulty increases when we want to split, merge, replicate, and relocate the UI across a set of heterogeneous devices, without the application intervention. Furthermore, using generic tools, e.g. to search for UI components or to save/restore them, is usually not feasible. We follow a novel approach for building UIs that overcomes these problems: using distributed file systems that export widgets to applications. In this paper we describe Omero, a UI server built along this line for the plan B operating system

Dynamic Objective and Advance Scheduling in Federated Grids

In this paper we present a dynamic mapping strategy for scheduling independent tasks in Federated Grids. This strategy is performed in two steps: first we calculate a new objective, and then we apply advance scheduling to meet the new objective. The results obtained by simulation show that the combination of these two steps reduces the makespan and increases the throughput. Thus, the mapping strategy proposed meets two of the most common objective functions of tasks scheduling problems: makespan and performance of the resources. The presented algorithm is easy to implement, unlike Genetic Algorithms is fast enough to be used in a realistic scheduling, and is efficient. In addition, the information the strategy needs can be provided by any Grid Information Service, and its does not require the deployment of complex prediction services or service level agreement: it can work in any Grid.

The Plan B OS for ubiquitous computing. Voice control, security, and terminals as case studies ☆

Abstract The conventional approach to building pervasive environments relies on middleware to integrate different systems. Instead, we have built a system that can deal with these environments by exporting system resources through distributed virtual file systems. This requires no middleware, simplifies interoperation, and permits the application of general purpose tools to any system resource. A constraint-based file system import mechanism allows the system to adapt to changes in the environment and permits users to customize the environment and tailor adaptations according to their needs. The system has been in use for over a year to carry out our daily work and is underlying the smart space that we built for our department. The system, and some novel services, including ubiquitous voice interfaces, a distributed security architecture, and remote terminals for smart spaces, are also described in this paper.

UbiTerm: a hand-held control-center for user's activity mobility

Current approaches handling users activity mobility address the problem by imposing system decisions instead of users indications in an attempt to reduce users distraction. At the same time, these traditional approaches introduce uniformity on the environment, thus preventing users to take full advantage of the computational resources found nearby. We describe an alternative architectural model that better solves the problem of supporting users mobility, reducing users distraction, and respecting users preferences. One of the key features of our solution is that users can directly control their activities. Thus, the PlanBs ubiquitous terminal (UbiTerm) provides activity control commands to users. In addition, to take appropriate actions when adapting the environment to user needs, the UbiTerm uses a context information mechanism. Finally, by using a programmable service for the remote execution of applications, the architecture can exploit local capabilities, provide support in different platforms, and fit activities to users preferences.

Dynamic Windows Scheduling with Reallocationä

We consider the Windows Scheduling problem. The problem is a restricted version of Unit-Fractions Bin Packing, and it is also called Inventory Replenishment in the context of Supply Chain. In brief, the problem is to schedule the use of communication channels that allow at most one transmission per time slot, to clients specified by a maximum delay between consecutive transmissions. We extend previous online models, where decisions are permanent, assuming that clients may be reallocated at some cost. We present three online reallocation algorithms for Windows Scheduling. We analyze one of them and we evaluate experimentally all three showing that, in practice, they achieve constant amortized reallocations with close to optimal channel usage. Our simulations also expose interesting trade-offs between reallocations and channel usage. To the best of our knowledge, this is the first study of Windows Scheduling with reallocation costs.