22 research outputs found
Cross organisational compatible workflows generation and execution
With the development of internet and electronics, the demand for electronic and online commerce has increased. This has, in turn, increased the demand for business process automation. Workflow has established itself as the technology used for business process automation. Since business organisations have to work in coordination with many other business organisations in order to succeed in business, the workflows of business organisations are expected to collaborate with those of other business organisations. Collaborating organisations can only proceed in business if they have compatible workflows. Therefore, there is a need for cross organisational workflow collaboration.
The dynamism and complexity of online and electronic business and high demand from the market leave the workflows prone to frequent changes. If a workflow changes, it has to be re-engineered as well as reconciled with the workflows of the collaborating organisations. To avoid the continuous re-engineering and reconciliation of workflows, and to reuse the existing units of work done, the focus has recently shifted from modeling workflows to automatic workflow generation.
Workflows must proceed to runtime execution, otherwise, the effort invested in the build time workflow modeling is wasted. Therefore, workflow management and collaboration systems must support workflow enactment and runtime workflow collaboration.
Although substantial research has been done in build-time workflow collaboration, automatic workflow generation, workflow enactment and runtime workflow collaboration, the integration of these highly inter-dependent aspects of workflow has not been considered in the literature. The research work presented in this thesis investigates the integration of these different aspects. The main focus of the research presented in this thesis is the creation of a framework that is able to generate multiple sets of compatible workflows for multiple collaborating organisations, from their OWLS process definitions and high level goals. The proposed framework also supports runtime enactment and runtime collaboration of the generated workflows
Open Workflows: Context-Dependent Construction and Execution in Mobile Wireless Settings
Existing workflow middleware executes tasks orchestrated by rules defined in a carefully handcrafted static graph. Workflow management systems have proved effective for service-oriented business automation in stable, wired infrastructures. We introduce a radically new paradigm for workflow construction and execution called open workflow to support goal-directed coordination among physically mobile people and devices that form a transient community over an ad hoc wireless network. The quintessential feature of the open workflow paradigm is dynamic construction and execution of custom, context-specific workflows in response to unpredictable and evolving circumstances by exploiting the knowledge and services available within a given spatiotemporal context. This work introduces the open workflow approach, surveys open research challenges in this promising new field, and presents algorithmic, architectural, and evaluation results for the first practical realization of an open workflow management system
Architecture for planning and execution of missions with fleets of unmanned vehicles
Esta tesis presenta contribuciones en el campo de la planificación automática y la
programación de tareas, la rama de la inteligencia artificial que se ocupa de la
realización de estrategias o secuencias de acciones típicamente para su ejecución por
parte de vehículos no tripulados, robots autónomos y/o agentes inteligentes. Cuando se
intenta alcanzar un objetivo determinado, la cooperación puede ser un aspecto clave. La
complejidad de algunas tareas requiere la cooperación entre varios agentes. Mas aún,
incluso si una tarea es lo suficientemente simple para ser llevada a cabo por un único
agente, puede usarse la cooperación para reducir el coste total de la misma. Para realizar
tareas complejas que requieren interacción física con el mundo real, los vehículos no
tripulados pueden ser usados como agentes. En los últimos años se han creado y utilizado
una gran diversidad de plataformas no tripuladas, principalmente vehículos que pueden
ser dirigidos sin un humano a bordo, tanto en misiones civiles como militares.
En esta tesis se aborda la aplicación de planificación simbólica de redes jerárquicas
de tareas (HTN planning, por sus siglas en inglés) en la resolución de problemas de
enrutamiento de vehículos (VRP, por sus siglas en inglés) [18], en dominios que implican
múltiples vehículos no tripulados de capacidades heterogéneas que deben cooperar para
alcanzar una serie de objetivos específicos.
La planificación con redes jerárquicas de tareas describe dominios utilizando una
descripción que descompone conjuntos de tareas en subconjuntos más pequeños de
subtareas gradualmente, hasta obtener tareas del más bajo nivel que no pueden ser
descompuestas y se consideran directamente ejecutables. Esta jerarquía es similar al modo
en que los humanos razonan sobre los problemas, descomponiéndolos en subproblemas
según el contexto, y por lo tanto suelen ser fáciles de comprender y diseñar.
Los problemas de enrutamiento de vehículos son una generalización del problema del
viajante (TSP, por sus siglas en inglés). La resolución del problema del viajante consiste
en encontrar la ruta más corta posible que permite visitar una lista de ciudades, partiendo
y acabando en la misma ciudad. Su generalización, el problema de enrutamiento de
vehículos, consiste en encontrar el conjunto de rutas de longitud mínima que permite
cubrir todas las ciudades con un determinado número de vehículos. Ambos problemas
cuentan con una fuerte componente combinatoria para su resolución, especialmente en el caso del VRP, por lo que su presencia en dominios que van a ser tratados con un planificador
HTN clásico supone un gran reto.
Para la aplicación de un planificador HTN en la resolución de problemas de enrutamiento
de vehículos desarrollamos dos métodos. En el primero de ellos presentamos un sistema
de optimización de soluciones basado en puntuaciones, que nos permite una nueva forma
de conexión entre un software especializado en la resolución del VRP con el planificador
HTN. Llamamos a este modo de conexión el método desacoplado, puesto que resolvemos
la componente combinatoria del problema de enrutamiento de vehículos mediante un
solucionador específico que se comunica con el planificador HTN y le suministra la
información necesaria para continuar con la descomposición de tareas. El segundo método
consiste en mejorar el planificador HTN utilizado para que sea capaz de resolver el
problema de enrutamiento de vehículos de la mejor forma posible sin tener que depender
de módulos de software externos. Llamamos a este modo el método acoplado. Con
este motivo hemos desarrollado un nuevo planificador HTN que utiliza un algoritmo de
búsqueda distinto del que se utiliza normalmente en planificadores de este tipo.
Esta tesis presenta nuevas contribuciones en el campo de la planificación con redes
jerárquicas de tareas para la resolución de problemas de enrutamiento de vehículos. Se
aplica una nueva forma de conexión entre dos planificadores independientes basada en
un sistema de cálculo de puntuaciones que les permite colaborar en la optimización de
soluciones, y se presenta un nuevo planificador HTN con un algoritmo de búsqueda distinto
al comúnmente utilizado. Se muestra la aplicación de estos dos métodos en misiones
civiles dentro del entorno de los Proyectos ARCAS y AEROARMS financiados por la
Comisión Europea y se presentan extensos resultados de simulación para comprobar la
validez de los dos métodos propuestos.This thesis presents contributions in the field of automated planning and scheduling,
the branch of artificial intelligence that concerns the realization of strategies or
action sequences typically for execution by unmanned vehicles, autonomous robots and/or
intelligent agents. When trying to achieve certain goal, cooperation may be a key aspect.
The complexity of some tasks requires the cooperation among several agents. Moreover,
even if the task is simple enough to be carried out by a single agent, cooperation can be
used to decrease the overall cost of the operation. To perform complex tasks that require
physical interaction with the real world, unmanned vehicles can be used as agents. In the
last years a great variety of unmanned platforms, mainly vehicles that can be driven without
a human on board, have been developed and used both in civil and military missions.
This thesis deals with the application of Hierarchical Task Network (HTN) planning
in the resolution of vehicle routing problems (VRP) [18] in domains involving multiple
heterogeneous unmanned vehicles that must cooperate to achieve specific goals.
HTN planning describes problem domains using a description that decomposes set of
tasks into subsets of smaller tasks and so on, obtaining low-level tasks that cannot be
further decomposed and are supposed to be executable. The hierarchy resembles the way
the humans reason about problems by decomposing them into sub-problems depending
on the context and therefore tend to be easy to understand and design.
Vehicle routing problems are a generalization of the travelling salesman problem (TSP).
The TSP consists on finding the shortest path that connects all the cities from a list, starting
and ending on the same city. The VRP consists on finding the set of minimal routes that
cover all cities by using a specific number of vehicles. Both problems have a combinatorial
nature, specially the VRP, that makes it very difficult to use a HTN planner in domains
where these problems are present.
Two approaches to use a HTN planner in domains involving the VRP have been tested.
The first approach consists on a score-based optimization system that allows us to apply a
new way of connecting a software specialized in the resolution of the VRP with the HTN
planner. We call this the decoupled approach, as we tackle the combinatorial nature of the
VRP by using a specialized solver that communicates with the HTN planner and provides
all the required information to do the task decomposition. The second approach consists on improving and enhancing the HTN planner to be capable of solving the VRP without
needing the use of an external software. We call this the coupled approach. For this reason,
a new HTN planner that uses a different search algorithm from these commonly used in
that type of planners has been developed and is presented in this work.
This thesis presents new contributions in the field of hierarchical task network planning
for the resolution of vehicle routing problem domains. A new way of connecting two
independent planning systems based on a score calculation system that lets them cooperate
in the optimization of the solutions is applied, and a new HTN planner that uses a different
search algorithm from that usually used in other HTN planners is presented. These two
methods are applied in civil missions in the framework of the ARCAS and AEROARMS
Projects funded by the European Commission. Extensive simulation results are presented
to test the validity of the two approaches
Pseudo-contractions as Gentle Repairs
Updating a knowledge base to remove an unwanted consequence is a challenging task. Some of the original sentences must be either deleted or weakened in such a way that the sentence to be removed is no longer entailed by the resulting set. On the other hand, it is desirable that the existing knowledge be preserved as much as possible, minimising the loss of information. Several approaches to this problem can be found in the literature. In particular, when the knowledge is represented by an ontology, two different families of frameworks have been developed in the literature in the past decades with numerous ideas in common but with little interaction between the communities: applications of AGM-like Belief Change and justification-based Ontology Repair. In this paper, we investigate the relationship between pseudo-contraction operations and gentle repairs. Both aim to avoid the complete deletion of sentences when replacing them with weaker versions is enough to prevent the entailment of the unwanted formula. We show the correspondence between concepts on both sides and investigate under which conditions they are equivalent. Furthermore, we propose a unified notation for the two approaches, which might contribute to the integration of the two areas
AUTOMATED COMPOSITION OF WEB SERVICES VIA PLANNING IN ASYNCHRONOUS DOMAINS\ud
The service-oriented paradigm promises a novel degree of interoperability between\ud
business processes, and is leading to a major shift in way distributed applications are\ud
designed and realized. While novel and more powerful services can be obtained, in such\ud
setting, by suitably orchestrating existing ones, manually developing such orchestrations\ud
is highly demanding, time-consuming and error-prone. Providing automated service\ud
composition tools is therefore essential to reduce the time to market of services, and\ud
ultimately to successfully enact the service-oriented approach.\ud
In this paper, we show that such tools can be realized based on the adoption and extension\ud
of powerful AI planning techniques, taking the “planning via model-checking” approach\ud
as a stepping stone. In this respect, this paper summarizes and substantially extends a\ud
research line that started early in this decade and has continued till now. Specifically, this\ud
work provides three key contributions.\ud
First, we describe a novel planning framework for the automated composition of Web\ud
services, which can handle services specified and implemented using industrial standard\ud
languages for business processes modeling and execution, like ws-bpel. Since these\ud
languages describe stateful Web services that rely on asynchronous communication\ud
primitives, a distinctive aspect of the presented framework is its ability to model and\ud
solve planning problems for asynchronous domains.\ud
Second, we formally spell out the theory underlying the framework, and provide algorithms\ud
to solve service composition in such framework, proving their correctness and\ud
completeness. The presented algorithms significantly extend state-of-the-art techniques\ud
for planning under uncertainty, by allowing the combination of asynchronous domains\ud
according to behavioral requirements.\ud
Third, we provide and discuss an implementation of the approach, and report extensive\ud
experimental results which demonstrate its ability to scale up to significant cases for\ud
which the manual development of ws-bpel composed services is far from trivial and time\ud
consuming
A MULTI-FUNCTIONAL PROVENANCE ARCHITECTURE: CHALLENGES AND SOLUTIONS
In service-oriented environments, services are put together in the form of a workflow with the aim of distributed problem solving.
Capturing the execution details of the services' transformations is a significant advantage of using workflows. These execution details, referred to as provenance information, are usually traced automatically and stored in provenance stores. Provenance data contains the data recorded by a workflow engine during a workflow execution. It identifies what data is passed between services, which services are involved, and how results are eventually generated for particular sets of input values.
Provenance information is of great importance and has found its way through areas in computer science such as: Bioinformatics, database, social, sensor networks, etc.
Current exploitation and application of provenance data is very limited as provenance systems started being developed for specific applications. Thus, applying learning and knowledge discovery methods to provenance data can provide rich and useful information on workflows and services.
Therefore, in this work, the challenges with workflows and services are studied to discover the possibilities and benefits of providing solutions by using provenance data.
A multifunctional architecture is presented which addresses the workflow and service issues by exploiting provenance data. These challenges include workflow composition, abstract workflow selection, refinement, evaluation, and graph model extraction. The specific contribution of the proposed architecture is its novelty in providing a basis for taking advantage of the previous execution details of services and workflows along with artificial intelligence and knowledge management techniques to resolve the major challenges regarding workflows. The presented architecture is application-independent and could be deployed in any area.
The requirements for such an architecture along with its building components are discussed. Furthermore, the responsibility of the components, related works and the implementation details of the architecture along with each component are presented
A graph-based framework for optimal semantic web service composition
Web services are self-described, loosely coupled software components that are network-accessible
through standardized web protocols, whose characteristics are described in XML. One of the key
promises of Web services is to provide better interoperability and to enable a faster integration
between systems. In order to generate robust service oriented architectures, automatic composition
algorithms are required in order to combine the functionality of many single services into composite
services that are able to respond to demanding user requests, even when there is no single service
capable of performing such task. Service composition consists of a combination of single services
into composite services that are executed in sequence or in a different order, imposed by a set of
control constructions that can be specified using standard languages such as OWL-s or BPEL4WS.
In the last years several papers have dealt with composition of web services. Some approaches treat
the service composition as a planning problem, where a sequence of actions lead from a initial state
to a goal state. However, most of these proposals have some drawbacks: high complexity, high
computational cost and inability to maximize the parallel execution of web services. Other
approaches consider the problem as a graph search problem, where search algorithms are applied
over a web service dependency graph in order to find a solution for a particular request. These
proposals are simpler than their counterparts and also many can exploit the parallel execution of
web services. However, most of these approaches rely on very complex dependency graphs that
have not been optimized to remove data redundancy, which may negatively affect the overall
performance and scalability of these techniques in large service registries. Therefore, it is necessary
to identify, characterize and optimize the different tasks involved in the automatic service
composition process in order to develop better strategies to efficiently obtain optimal solutions. The
main goal of this dissertation is to develop a graph-based framework for automatic service
composition that generate optimal input-output based compositions not only in terms of complexity
of the solutions, but also in terms of overall quality of service solutions. More specifically, the
objectives of this thesis are: (1) Analysis of the characteristics of services and compositions. The
aim of this objective is to characterize and identify the main steps that are part for the service
composition process. (2) Framework for automatic graph-based composition. This objective will
focus on developing a framework that enables the efficient input-output based service composition,
exploring the integration with other tasks that are part of the composition process, such as service
discovery. (3) Development of optimal algorithms for automatic service composition. This objective
focuses on the development of a set of algorithms and optimization techniques for the generation of
optimal compositions, optimizing the complexity of the solutions and the overall Quality-of-
Service. (4) Validation of the algorithms with standard datasets so they can be compared with other
proposals