6,401 research outputs found
Generic access to symbolic computing services
Symbolic computation is one of the computational domains that requires large computational
resources. Computer Algebra Systems (CAS), the main tools used for symbolic
computations, are mainly designed to be used as software tools installed on standalone
machines that do not provide the required resources for solving large symbolic computation
problems. In order to support symbolic computations an infrastructure built upon
massively distributed computational environments must be developed.
Building an infrastructure for symbolic computations requires a thorough analysis of
the most important requirements raised by the symbolic computation world and must
be built based on the most suitable architectural styles and technologies. The architecture
that we propose is composed of several main components: the Computer Algebra
System (CAS) Server that exposes the functionality implemented by one or more supporting
CASs through generic interfaces of Grid Services; the Architecture for Grid
Symbolic Services Orchestration (AGSSO) Server that allows seamless composition of
CAS Server capabilities; and client side libraries to assist the users in describing workflows
for symbolic computations directly within the CAS environment. We have also
designed and developed a framework for automatic data management of mathematical
content that relies on OpenMath encoding.
To support the validation and fine tuning of the system we have developed a simulation
platform that mimics the environment on which the architecture is deployed
CREOLE: a Universal Language for Creating, Requesting, Updating and Deleting Resources
In the context of Service-Oriented Computing, applications can be developed
following the REST (Representation State Transfer) architectural style. This
style corresponds to a resource-oriented model, where resources are manipulated
via CRUD (Create, Request, Update, Delete) interfaces. The diversity of CRUD
languages due to the absence of a standard leads to composition problems
related to adaptation, integration and coordination of services. To overcome
these problems, we propose a pivot architecture built around a universal
language to manipulate resources, called CREOLE, a CRUD Language for Resource
Edition. In this architecture, scripts written in existing CRUD languages, like
SQL, are compiled into Creole and then executed over different CRUD interfaces.
After stating the requirements for a universal language for manipulating
resources, we formally describe the language and informally motivate its
definition with respect to the requirements. We then concretely show how the
architecture solves adaptation, integration and coordination problems in the
case of photo management in Flickr and Picasa, two well-known service-oriented
applications. Finally, we propose a roadmap for future work.Comment: In Proceedings FOCLASA 2010, arXiv:1007.499
Actor-network procedures: Modeling multi-factor authentication, device pairing, social interactions
As computation spreads from computers to networks of computers, and migrates
into cyberspace, it ceases to be globally programmable, but it remains
programmable indirectly: network computations cannot be controlled, but they
can be steered by local constraints on network nodes. The tasks of
"programming" global behaviors through local constraints belong to the area of
security. The "program particles" that assure that a system of local
interactions leads towards some desired global goals are called security
protocols. As computation spreads beyond cyberspace, into physical and social
spaces, new security tasks and problems arise. As networks are extended by
physical sensors and controllers, including the humans, and interlaced with
social networks, the engineering concepts and techniques of computer security
blend with the social processes of security. These new connectors for
computational and social software require a new "discipline of programming" of
global behaviors through local constraints. Since the new discipline seems to
be emerging from a combination of established models of security protocols with
older methods of procedural programming, we use the name procedures for these
new connectors, that generalize protocols. In the present paper we propose
actor-networks as a formal model of computation in heterogenous networks of
computers, humans and their devices; and we introduce Procedure Derivation
Logic (PDL) as a framework for reasoning about security in actor-networks. On
the way, we survey the guiding ideas of Protocol Derivation Logic (also PDL)
that evolved through our work in security in last 10 years. Both formalisms are
geared towards graphic reasoning and tool support. We illustrate their workings
by analysing a popular form of two-factor authentication, and a multi-channel
device pairing procedure, devised for this occasion.Comment: 32 pages, 12 figures, 3 tables; journal submission; extended
references, added discussio
Regulating Data Exchange in Service Oriented Applications
We define a type system for COWS, a formalism for specifying and combining services, while modelling their dynamic behaviour. Our types permit to express policies constraining data exchanges in terms of sets of service partner names attachable to each single datum. Service programmers explicitly write only the annotations necessary to specify the wanted policies for communicable data, while a type inference system (statically) derives the minimal additional annotations that ensure consistency of services initial configuration. Then, the language dynamic semantics only performs very simple checks to authorize or block communication. We prove that the type system and the operational semantics are sound. As a consequence, we have the following data protection property: services always comply with the policies regulating the exchange of data among interacting services. We illustrate our approach through a simplified but realistic scenario for a service-based electronic marketplace
COWS: A Timed Service-Oriented Calculus
COWS (Calculus for Orchestration of Web Services) is a foundational language for Service Oriented Computing that combines in an original way a number of ingredients borrowed from well-known process calculi, e.g. asynchronous communication, polyadic synchronization, pattern matching, protection, delimited receiving and killing activities, while resulting different from any of them. In this paper, we extend COWS with timed orchestration constructs, this way we obtain a language capable of completely formalizing the semantics of WS-BPEL, the ‘de facto’ standard language for orchestration of web services. We present the semantics of the extended language and illustrate its peculiarities and expressiveness by means of several examples
A Logical Verification Methodology for Service-Oriented Computing
We introduce a logical verification methodology for checking behavioural properties of service-oriented computing systems. Service properties are described by means of SocL, a branching-time temporal logic that we have specifically designed to express in an effective way distinctive aspects of services, such as, e.g., acceptance of a request, provision of a response, and correlation among service requests and responses. Our approach allows service properties to be expressed in such a way that
they can be independent of service domains and specifications. We show an instantiation of our general methodology that uses the formal language COWS to conveniently specify services and the expressly developed software tool CMC to assist the user in the task of verifying SocL formulae over service specifications. We demonstrate feasibility and effectiveness of our methodology by means of the specification and the analysis of a case study in the automotive domain
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