4,812 research outputs found
A Type-Safe Model of Adaptive Object Groups
Services are autonomous, self-describing, technology-neutral software units
that can be described, published, discovered, and composed into software
applications at runtime. Designing software services and composing services in
order to form applications or composite services requires abstractions beyond
those found in typical object-oriented programming languages. This paper
explores service-oriented abstractions such as service adaptation, discovery,
and querying in an object-oriented setting. We develop a formal model of
adaptive object-oriented groups which offer services to their environment.
These groups fit directly into the object-oriented paradigm in the sense that
they can be dynamically created, they have an identity, and they can receive
method calls. In contrast to objects, groups are not used for structuring code.
A group exports its services through interfaces and relies on objects to
implement these services. Objects may join or leave different groups. Groups
may dynamically export new interfaces, they support service discovery, and they
can be queried at runtime for the interfaces they support. We define an
operational semantics and a static type system for this model of adaptive
object groups, and show that well-typed programs do not cause
method-not-understood errors at runtime.Comment: In Proceedings FOCLASA 2012, arXiv:1208.432
A Geometric Approach to the Problem of Unique Decomposition of Processes
This paper proposes a geometric solution to the problem of prime
decomposability of concurrent processes first explored by R. Milner and F.
Moller in [MM93]. Concurrent programs are given a geometric semantics using
cubical areas, for which a unique factorization theorem is proved. An effective
factorization method which is correct and complete with respect to the
geometric semantics is derived from the factorization theorem. This algorithm
is implemented in the static analyzer ALCOOL.Comment: 15 page
Leveraging OpenStack and Ceph for a Controlled-Access Data Cloud
While traditional HPC has and continues to satisfy most workflows, a new
generation of researchers has emerged looking for sophisticated, scalable,
on-demand, and self-service control of compute infrastructure in a cloud-like
environment. Many also seek safe harbors to operate on or store sensitive
and/or controlled-access data in a high capacity environment.
To cater to these modern users, the Minnesota Supercomputing Institute
designed and deployed Stratus, a locally-hosted cloud environment powered by
the OpenStack platform, and backed by Ceph storage. The subscription-based
service complements existing HPC systems by satisfying the following unmet
needs of our users: a) on-demand availability of compute resources, b)
long-running jobs (i.e., days), c) container-based computing with
Docker, and d) adequate security controls to comply with controlled-access data
requirements.
This document provides an in-depth look at the design of Stratus with respect
to security and compliance with the NIH's controlled-access data policy.
Emphasis is placed on lessons learned while integrating OpenStack and Ceph
features into a so-called "walled garden", and how those technologies
influenced the security design. Many features of Stratus, including tiered
secure storage with the introduction of a controlled-access data "cache",
fault-tolerant live-migrations, and fully integrated two-factor authentication,
depend on recent OpenStack and Ceph features.Comment: 7 pages, 5 figures, PEARC '18: Practice and Experience in Advanced
Research Computing, July 22--26, 2018, Pittsburgh, PA, US
Modeling visual attention on scenes
International audienceLa modélisation computationelle de l'attention visuelle connaît actuellement un essor considérable. Les premières modèles, purement basés sur l'attention dite exogène, permettent de calculer une carte de saillance indiquant les zones d'intérêt visuel d'une image. Cependant, afin d'améliorer cette prédiction, il s'avère nécessaire de prendre en compte des informations de plus haut niveaux relatives à l'attention endogène, c'est à dire des informations liées aux processus cognitifs. Afin de rendre compte de cette problématique, le présent article décrit un certain nombre de modèles exogènes ainsi que des modèles intégrant de la connaissance a priori. Les méthodes d'évaluation des performances sont également décrites. Afin d'aller plus loin dans la modélisation et dans la compréhension des processus cognitifs, de nouvelles perspectives et direction d'études sont exposées
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