28 research outputs found
Modelo de arquitectura para gestión cooperativa de sistemas y servicios distribuidos basado en agentes autónomos
La creciente complejidad, heterogeneidad y dinamismo inherente a las redes de telecomunicaciones,
los sistemas distribuidos y los servicios avanzados de información
y comunicación emergentes, así como el incremento de su criticidad e importancia
estratégica, requieren la adopción de tecnologías cada vez más sofisticadas para su
gestión, su coordinación y su integración por parte de los operadores de red, los
proveedores de servicio y las empresas, como usuarios finales de los mismos, con el
fin de garantizar niveles adecuados de funcionalidad, rendimiento y fiabilidad.
Las estrategias de gestión adoptadas tradicionalmente adolecen de seguir modelos
excesivamente estáticos y centralizados, con un elevado componente de supervisión
y difícilmente escalables. La acuciante necesidad por flexibilizar esta gestión y
hacerla a la vez más escalable y robusta, ha provocado en los últimos años un considerable
interés por desarrollar nuevos paradigmas basados en modelos jerárquicos y
distribuidos, como evolución natural de los primeros modelos jerárquicos débilmente
distribuidos que sucedieron al paradigma centralizado. Se crean así nuevos modelos
como son los basados en Gestión por Delegación, en el paradigma de código móvil,
en las tecnologías de objetos distribuidos y en los servicios web. Estas alternativas
se han mostrado enormemente robustas, flexibles y escalables frente a las estrategias
tradicionales de gestión, pero continúan sin resolver aún muchos problemas.
Las líneas actuales de investigación parten del hecho de que muchos problemas
de robustez, escalabilidad y flexibilidad continúan sin ser resueltos por el paradigma
jerárquico-distribuido, y abogan por la migración hacia un paradigma cooperativo
fuertemente distribuido. Estas líneas tienen su germen en la Inteligencia Artificial
Distribuida (DAI) y, más concretamente, en el paradigma de agentes autónomos y
en los Sistemas Multi-agente (MAS). Todas ellas se perfilan en torno a un conjunto
de objetivos que pueden resumirse en alcanzar un mayor grado de autonomía
en la funcionalidad de la gestión y una mayor capacidad de autoconfiguración que
resuelva los problemas de escalabilidad y la necesidad de supervisión presentes en
los sistemas actuales, evolucionar hacia técnicas de control fuertemente distribuido
y cooperativo guiado por la meta y dotar de una mayor riqueza semántica a los
modelos de información. Cada vez más investigadores están empezando a utilizar
agentes para la gestión de redes y sistemas distribuidos. Sin embargo, los límites establecidos
en sus trabajos entre agentes móviles (que siguen el paradigma de código móvil) y agentes autónomos (que realmente siguen el paradigma cooperativo) resultan
difusos. Muchos de estos trabajos se centran en la utilización de agentes móviles,
lo cual, al igual que ocurría con las técnicas de código móvil comentadas anteriormente,
les permite dotar de un mayor componente dinámico al concepto tradicional
de Gestión por Delegación. Con ello se consigue flexibilizar la gestión, distribuir la
lógica de gestión cerca de los datos y distribuir el control. Sin embargo se permanece
en el paradigma jerárquico distribuido. Si bien continúa sin definirse aún una
arquitectura de gestión fiel al paradigma cooperativo fuertemente distribuido, estas
líneas de investigación han puesto de manifiesto serios problemas de adecuación en
los modelos de información, comunicación y organizativo de las arquitecturas de
gestión existentes.
En este contexto, la tesis presenta un modelo de arquitectura para gestión holónica
de sistemas y servicios distribuidos mediante sociedades de agentes autónomos,
cuyos objetivos fundamentales son el incremento del grado de automatización asociado
a las tareas de gestión, el aumento de la escalabilidad de las soluciones de
gestión, soporte para delegación tanto por dominios como por macro-tareas, y un
alto grado de interoperabilidad en entornos abiertos. A partir de estos objetivos
se ha desarrollado un modelo de información formal de tipo semántico, basado en
lógica descriptiva que permite un mayor grado de automatización en la gestión en
base a la utilización de agentes autónomos racionales, capaces de razonar, inferir
e integrar de forma dinámica conocimiento y servicios conceptualizados mediante
el modelo CIM y formalizados a nivel semántico mediante lógica descriptiva. El
modelo de información incluye además un “mapping” a nivel de meta-modelo de
CIM al lenguaje de especificación de ontologías OWL, que supone un significativo
avance en el área de la representación y el intercambio basado en XML de modelos
y meta-información. A nivel de interacción, el modelo aporta un lenguaje de
especificación formal de conversaciones entre agentes basado en la teoría de actos
ilocucionales y aporta una semántica operacional para dicho lenguaje que facilita la
labor de verificación de propiedades formales asociadas al protocolo de interacción.
Se ha desarrollado también un modelo de organización holónico y orientado a roles
cuyas principales características están alineadas con las demandadas por los servicios
distribuidos emergentes e incluyen la ausencia de control central, capacidades
de reestructuración dinámica, capacidades de cooperación, y facilidades de adaptación
a diferentes culturas organizativas. El modelo incluye un submodelo normativo
adecuado al carácter autónomo de los holones de gestión y basado en las lógicas
modales deontológica y de acción.---ABSTRACT---The growing complexity, heterogeneity and dynamism inherent in telecommunications
networks, distributed systems and the emerging advanced information and
communication services, as well as their increased criticality and strategic importance,
calls for the adoption of increasingly more sophisticated technologies for their
management, coordination and integration by network operators, service providers
and end-user companies to assure adequate levels of functionality, performance and
reliability.
The management strategies adopted traditionally follow models that are too
static and centralised, have a high supervision component and are difficult to scale.
The pressing need to flexibilise management and, at the same time, make it more
scalable and robust recently led to a lot of interest in developing new paradigms
based on hierarchical and distributed models, as a natural evolution from the first
weakly distributed hierarchical models that succeeded the centralised paradigm.
Thus new models based on management by delegation, the mobile code paradigm,
distributed objects and web services came into being. These alternatives have turned
out to be enormously robust, flexible and scalable as compared with the traditional
management strategies. However, many problems still remain to be solved.
Current research lines assume that the distributed hierarchical paradigm has as
yet failed to solve many of the problems related to robustness, scalability and flexibility
and advocate migration towards a strongly distributed cooperative paradigm.
These lines of research were spawned by Distributed Artificial Intelligence (DAI)
and, specifically, the autonomous agent paradigm and Multi-Agent Systems (MAS).
They all revolve around a series of objectives, which can be summarised as achieving
greater management functionality autonomy and a greater self-configuration
capability, which solves the problems of scalability and the need for supervision that
plague current systems, evolving towards strongly distributed and goal-driven cooperative
control techniques and semantically enhancing information models. More
and more researchers are starting to use agents for network and distributed systems
management. However, the boundaries established in their work between mobile
agents (that follow the mobile code paradigm) and autonomous agents (that really
follow the cooperative paradigm) are fuzzy. Many of these approximations focus on the use of mobile agents, which, as was the case with the above-mentioned mobile
code techniques, means that they can inject more dynamism into the traditional
concept of management by delegation. Accordingly, they are able to flexibilise management,
distribute management logic about data and distribute control. However,
they remain within the distributed hierarchical paradigm. While a management architecture
faithful to the strongly distributed cooperative paradigm has yet to be
defined, these lines of research have revealed that the information, communication
and organisation models of existing management architectures are far from adequate.
In this context, this dissertation presents an architectural model for the holonic
management of distributed systems and services through autonomous agent societies.
The main objectives of this model are to raise the level of management task
automation, increase the scalability of management solutions, provide support for
delegation by both domains and macro-tasks and achieve a high level of interoperability
in open environments. Bearing in mind these objectives, a descriptive
logic-based formal semantic information model has been developed, which increases
management automation by using rational autonomous agents capable of reasoning,
inferring and dynamically integrating knowledge and services conceptualised
by means of the CIM model and formalised at the semantic level by means of descriptive
logic. The information model also includes a mapping, at the CIM metamodel
level, to the OWL ontology specification language, which amounts to a significant
advance in the field of XML-based model and metainformation representation and
exchange. At the interaction level, the model introduces a formal specification language
(ACSL) of conversations between agents based on speech act theory and contributes
an operational semantics for this language that eases the task of verifying
formal properties associated with the interaction protocol. A role-oriented holonic
organisational model has also been developed, whose main features meet the requirements
demanded by emerging distributed services, including no centralised control,
dynamic restructuring capabilities, cooperative skills and facilities for adaptation to
different organisational cultures. The model includes a normative submodel adapted
to management holon autonomy and based on the deontic and action modal logics
COMPONENT TECHNOLOGIES AND THEIR IMPACT UPON SOFTWARE DEVELOPMENT
Software development is beset with problems relating to development productivity, resulting in
projects delivered late and over budget. While the term software engineering was first introduced
in the late sixties, its current state reflects no other engineering discipline. Component-orientation
has been proposed as a technique to address the problems of development productivity and much
industrial literature extols the benefits of a component-oriented approach to software
development.
This research programme assesses the use of component technologies within industrial software
development. From this assessment, consideration is given to how organisations can best adopt
such techniques. Initial work focuses upon the nature of component-orientation, drawing from the
considerable body of industrial literature in the area. Conventional wisdom regarding componentorientation
is identified from the review. Academic literature relevant to the research programme
focuses upon knowledge regarding the assessment of software technologies and models for the
adoption of emergent technologies. The method pays particular attention to literature concerning
practitioner focussed research, in particular case studies. The application of the case study method
is demonstrated.
The study of two industrial software development projects enables an examination of specific
propositions related to the effect of using component technologies. Each case study is presented,
and the impact of component-orientation is each case is demonstrated. Theories regarding the
impact of component technologies upon software development are drawn from case study results.
These theories are validated through a survey of practitioners. This enabled further examination
of experience in component-based development and also understanding how developers learn
about the techniques.
A strategy for the transfer of research findings into organisational knowledge focuses upon the
packaging of previous experience in the use of component-orientation in such a way that it was
usable by other developers. This strategy returns to adoption theories in light of the research
findings and identifies a pattern-based approach as the most suitable for the research aims. A
pattern language, placed in the context of the research programme, is developed from this
strategy.
Research demonstrates that component-orientation undoubtedly does affect the development
process, and it is necessary to challenge conventional wisdom regarding their use. While
component-orientation provides the mechanisms for increased productivity in software
development, these benefits cannot be exploited without a sound knowledge base around the
domain
A distributed intelligent network based on CORBA and SCTP
The telecommunications services marketplace is undergoing radical change due to the rapid convergence and evolution of telecommunications and computing technologies. Traditionally telecommunications service providers’ ability to deliver network services has been through Intelligent Network (IN) platforms. The IN may be characterised as envisioning centralised processing of distributed service requests from a limited number of quasi-proprietary nodes with inflexible connections to the network management system and third party networks. The nodes are inter-linked by the operator’s highly reliable but expensive SS.7 network. To leverage this technology as the core of new multi-media services several key technical challenges must be overcome. These include: integration of the IN with new technologies for service delivery, enhanced integration with network management services, enabling third party service providers and reducing operating costs by using more general-purpose computing and networking equipment. In this thesis we present a general architecture that defines the framework and techniques required to realise an open, flexible, middleware (CORBA)-based distributed intelligent network (DIN). This extensible architecture naturally encapsulates the full range of traditional service network technologies, for example IN (fixed network), GSM-MAP and CAMEL. Fundamental to this architecture are mechanisms for inter-working with the existing IN infrastructure, to enable gradual migration within a domain and inter-working between IN and DIN domains. The DIN architecture compliments current research on third party service provision, service management and integration Internet-based servers. Given the dependence of such a distributed service platform on the transport network that links computational nodes, this thesis also includes a detailed study of the emergent IP-based telecommunications transport protocol of choice, Stream Control Transmission Protocol (SCTP). In order to comply with the rigorous performance constraints of this domain, prototyping, simulation and analytic modelling of the DIN based on SCTP have been carried out. This includes the first detailed analysis of the operation of SCTP congestion controls under a variety of network conditions leading to a number of suggested improvements in the operation of the protocol. Finally we describe a new analytic framework for dimensioning networks with competing multi-homed SCTP flows in a DIN. This framework can be used for any multi-homed SCTP network e.g. one transporting SIP or HTTP