Integrating formal reasoning into component-based approach to reconfigurable distributed systems

Distributed computing is becoming ubiquitous in recent years in many areas, especially the scientific and industrial ones, where the processing power - even that of supercomputers - never seems to be enough. Grid systems were born out of necessity, and had to grow quickly to meet requirements which evolved over time, becoming today’s complex systems. Even the simplest distributed system nowadays is expected to have some basic functionalities, such as resources and execution management, security and optimization features, data control, etc. The complexity of Grid applications is also accentuated by their distributed nature, making them some of the most elaborate systems to date. It is often too easy that these intricate systems happen to fall in some kind of failure, it being a software bug, or plain simple human error; and if such a failure occurs, it is not always the case that the system can recover from it, possibly meaning hours of wasted computational power. In this thesis, some of the problems which are at the core of the development and mainte- nance of Grid software applications are addressed by introducing novel and solid approaches to their solution. The difficulty of Grid systems to deal with unforeseen and unexpected cir- cumstances resulting from dynamic reconfiguration can be identified. Such problems are often related to the fact that Grid applications are large, distributed and prone to resource failures. This research has produced a methodology for the solution of this problem by analysing the structure of distributed systems and their reliance on the environment which they sit upon, often overlooked when dealing with these types of scenarios. It is concluded that the way that Grid applications interact with the infrastructure is not sufficiently addressed and a novel approach is developed in which formal verification methods are integrated with distributed applications development and deployment in a way that includes the environment. This approach allows for reconfiguration scenarios in distributed applications to proceed in a safe and controlled way, as demonstrated by the development of a prototype application

Bringing social reality to multiagent and service architectures : practical reductions for monitoring of deontic-logic and constitutive norms

As distributed systems grow in complexity, the interactions among individuals (agents, services) of such systems become increasingly more complex and therefore more difficult to constrain and monitor. We propose to view such systems as socio-technical systems, in which organisational and institutional concepts, such as norms, can be applied to improve not only control on the components but also their autonomy by the definition of soft rather than hard constraints. Norms can be described as rules that guide the behavior of individual agents pertaining to groups that abide to them, either by explicit or implicit support. The study of norms, and regulatory systems in general, in their many forms -e.g. social norms, conventions, laws, regulations- has been of interest since the beginning of philosophy, but has seen a lot of evolution during the 20th century due to the progress in the philosophy of language, especially concerning speech acts and deontic logic. Although there is a myriad of definitions and related terminologies about the concept of norm, and as such there are many perspectives on how to analyse their impact, a common denominator is that norms constrain the behaviour of groups of agents in a way that each individual agent can build, with a fair degree of confidence, expectations on how each of their counterparts will behave in the situations that the norms are meant to cover. For example, on a road each driver expects everybody else to drive on only one side of the road (right or left, depending on the country). Therefore, normative contexts, usually wrapped in the form of institutions, are effective mechanisms to ensure the stability of a complex system such as an organisation, a society, or even of electronic systems. The latter has been an object of interest in the field of Artificial Intelligence, and it has been seen as a paradigm of coordination among electronic agents either in multi-agent systems or in service-oriented architectures. In order to apply norms to electronic systems, research has come up with abstractions of normative systems. In some cases these abstractions are based on regimented systems with flexible definitions of the notion of norm, in order to include meanings of the concept with a coarse-grained level of logic formality such as conventions. Other approaches, on the other hand, propose the use of deontic logic for describing, from a more theoretical perspective, norm-governed interaction environments. In both cases, the purpose is to enable the monitoring and enforcement of norms on systems that include -although not limited to- electronic agents. In the present dissertation we will focus on the latter type, focusing on preserving the deontic aspect of norms. Monitoring in norm-governed systems requires making agents aware of: 1) what their normative context is, i.e. which obligations, permissions and prohibitions are applicable to each of them and how they are updated and triggered; and 2) what their current normative status is, i.e. which norms are active, and in what instances they are being fullfilled or violated, in order words, what their social -institutional- reality is. The current challenge is on designing systems that allow computational components to infer both the normative context and social reality in real-time, based on a theoretical formalism that makes such inferences sound and correct from a philosophical perspective. In the scope of multi-agent systems, many are the approaches proposed and implemented that full these requirements up to this date. However, the literature is still lacking a proposal that is suited to the current state-of-the-art in service-oriented architectures, more focused nowadays on automatically scalable, polyglot amalgams of lightweight services with extremely simple communication and coordination mechanisms- a trend that is being called “microservices”. This dissertation tackles this issue, by 1) studying what properties we can infer from distributed systems that allow us to treat them as part of a socio-technical system, and 2) analysing which mechanisms we can provide to distributed systems so that they can properly act as socio-technical systems. The main product of the thesis is therefore a collection of computational elements required for formally grounded and real-time e¬fficient understanding and monitoring of normative contexts, more specially: 1. An ontology of events to properly model the inputs from the external world and convert them into brute facts or institutional events; 2. A lightweight language for norms, suitable for its use in distributed systems; 3. An especially tailored formalism for the detection of social reality, based on and reducible to deontic logic with support for constitutive norms; 4. A reduction of such formalism to production rule systems; and 5. One or more implementations of this reduction, proven to e¬fficiently work on several scenarios. This document presents the related work, the rationale and the design/implementation of each one of these elements. By combining them, we are able to present novel, relevant work that enables the application of normative reasoning mechanisms in realworld systems in the form of a practical reasoner. Of special relevance is the fact that the work presented in this dissertation simplifies, while preserving formal soundness, theoretically complex forms of reasoning. Nonetheless, the use of production systems as the implementation-level materialisation of normative monitoring allows our work to be applied in any language and/or platform available, either in the form of rule engines, ECA rules or even if-then-else patterns. The work presented has been tested and successfully used in a wide range of domains and actual applications. The thesis also describes how our mechanisms have been applied to practical use cases based on their integration into distributed eldercare management and to commercial games.Con el incremento en la complejidad de los sistemas distribuidos, las interacciones entre los individuos (agentes, servicios) de dichos sistemas se vuelven más y más complejas y, por ello, más difíciles de restringir y monitorizar. Proponemos ver a estos sistemas como sistemas socio-técnicos, en los que conceptos organizacionales e institucionales (como las normas) pueden aplicarse para mejorar no solo el control sobre los componentes sino también su autonomía mediante la definición de restricciones débiles (en vez de fuertes). Las Normas se pueden describir como reglas que guían el comportamiento de agentes individuales que pertenecen a grupos que las siguen, ya sea con un apoyo explícito o implícito. El estudio de las normas y de los sistemas regulatorios en general y en sus formas diversas -normas sociales, convenciones, leyes, reglamentos- ha sido de interés para los eruditos desde los inicios de la filosofía, pero ha sufrido una evolución mayor durante el siglo 20 debido a los avances en filosofía del lenguaje, en especial los relacionados con los actos del habla -speech acts en inglés- y formas deónticas de la lógica modal. Aunque hay una gran variedad de definiciones y terminología asociadas al concepto de norma, y por ello existen varios puntos de vista sobre como analizar su impacto, el denominador común es que las normas restringen el comportamiento de grupos de agentes de forma que cada agente individual puede construir, con un buen nivel de confianza, expectativas sobre cómo cada uno de los otros actores se comportará en las situaciones que las normas han de cubrir. Por ejemplo, en una carretera cada conductor espera que los demás conduzcan solo en un lado de la carretera (derecha o izquierda, dependiendo del país). Por lo tanto, los contextos normativos, normalmente envueltos en la forma de instituciones, constituyen mecanismos efectivos para asegurar la estabilidad de un sistema complejo como una organización, una sociedad o incluso un sistema electrónico. Lo último ha sido objeto de estudio en el campo de la Inteligencia Artificial, y se ha visto como paradigma de coordinación entre agentes electrónicos, tanto en sistemas multiagentes como en arquitecturas orientadas a servicios. Para aplicar normas en sistemas electrónicos, los investigadores han creado abstracciones de sistemas normativos. En algunos casos estas abstracciones se basan en sistemas regimentados con definiciones flexibles del concepto de norma para poder influir algunos significados del concepto con un menor nivel de granularidad formal como es el caso de las convenciones. Otras aproximaciones proponen el uso de lógica deóntica para describir, desde un punto de vista más teórico, entornos de interacción gobernados por normas. En ambos casos el propósito es el permitir la monitorización y la aplicación de las normas en sistemas que incluyen -aunque no están limitados a- agentes electrónicos. En el presente documento nos centraremos en el segundo tipo, teniendo cuidado en mantener el aspecto deóntico de las normas. La monitorización en sistemas gobernados por normas requiere el hacer a los agentes conscientes de: 1) cual es su contexto normativo, es decir, que obligaciones permisos y prohibiciones se aplican a cada uno de ellos y cómo se actualizan y activan; y 2) cual es su estado normativo actual, esto es, que normas están activas, y que instancias están siendo cumplidas o violadas, en definitiva, cual es su realidad social -o institucional-. En la actualidad el reto consiste en diseñar sistemas que permiten inferir a componentes computacionales tanto el contexto normativo como la realidad social en tiempo real, basándose en un formalismo teórico que haga que dichas inferencias sean correctas y bien fundamentadas desde el punto de vista filosófico. En el ámbito de los sistemas multiagente existen muchas aproximaciones propuestas e implementadas que cubren estos requisitos. Sin embargo, esta literatura aun carece de una propuesta que sea adecuada para la tecnología de las arquitecturas orientadas a servicios, que están más centradas en amalgamas políglotas y escalables de servicios ligeros con mecanismos de coordinación y comunicación extremadamente simples, una tendencia moderna que lleva el nombre de microservicios. Esta tesis aborda esta problemática 1) estudiando que propiedades podemos inferir de los sistemas distribuidos que nos permitan tratarlos como parte de un sistema sociotécnico, y 2) analizando que mecanismos podemos proporcionar a los sistemas distribuidos de forma que puedan actuar de forma correcta como sistemas socio-técnicos. El producto principal de la tesis es, por tanto, una colección de elementos computacionales requeridos para la monitorización e interpretación e_cientes en tiempo real y con clara base formal. En concreto: 1. Una ontología de eventos para modelar adecuadamente las entradas del mundo exterior y convertirlas en hechos básicos o en eventos institucionales; 2. Un lenguaje de normas ligero y sencillo, adecuado para su uso en arquitecturas orientadas a servicios; 3. Un formalismo especialmente adaptado para la detección de la realidad social, basado en y reducible a lógica deóntica con soporte para normas constitutivas; 4. Una reducción de ese formalismo a sistemas de reglas de producción; y 5. Una o más implementaciones de esta reducción, de las que se ha probado que funcionan eficientemente en distintos escenarios. Este documento presenta el estado del arte relacionado, la justificación y el diseño/implementación para cada uno de esos elementos. Al combinarlos, somos capaces de presentar trabajo novedoso y relevante que permite la aplicación de mecanismos de razonamiento normativo en sistemas del mundo real bajo la forma de un razonador práctico. De especial relevancia es el hecho de que el trabajo presentado en este documento simplifica formas complejas y teóricas de razonamiento preservando la correctitud formal. El uso de sistemas de reglas de producción como la materialización a nivel de implementación del monitoreo normativo permite que nuestro trabajo se pueda aplicar a cualquier lenguaje o plataforma disponible, ya sea en la forma de motores de reglas, reglas ECA o incluso patrones si-entonces. El trabajo presentado ha sido probado y usado con éxito en un amplio rango de dominios y aplicaciones prácticas. La tesis describe como nuestros mecanismos se han aplicado a casos prácticos de uso basados en su integración en la gestión distribuida de pacientes de edad avanzada o en el sector de los videojuegos comerciales.Postprint (published version

From Euclidean Geometry to Knots and Nets

This document is the Accepted Manuscript of an article accepted for publication in Synthese. Under embargo until 19 September 2018. The final publication is available at Springer via https://doi.org/10.1007/s11229-017-1558-x.This paper assumes the success of arguments against the view that informal mathematical proofs secure rational conviction in virtue of their relations with corresponding formal derivations. This assumption entails a need for an alternative account of the logic of informal mathematical proofs. Following examination of case studies by Manders, De Toffoli and Giardino, Leitgeb, Feferman and others, this paper proposes a framework for analysing those informal proofs that appeal to the perception or modification of diagrams or to the inspection or imaginative manipulation of mental models of mathematical phenomena. Proofs relying on diagrams can be rigorous if (a) it is easy to draw a diagram that shares or otherwise indicates the structure of the mathematical object, (b) the information thus displayed is not metrical and (c) it is possible to put the inferences into systematic mathematical relation with other mathematical inferential practices. Proofs that appeal to mental models can be rigorous if the mental models can be externalised as diagrammatic practice that satisfies these three conditions.Peer reviewe

The Philosophical Foundations of PLEN: A Protocol-theoretic Logic of Epistemic Norms

In this dissertation, I defend the protocol-theoretic account of epistemic norms. The protocol-theoretic account amounts to three theses: (i) There are norms of epistemic rationality that are procedural; epistemic rationality is at least partially defined by rules that restrict the possible ways in which epistemic actions and processes can be sequenced, combined, or chosen among under varying conditions. (ii) Epistemic rationality is ineliminably defined by procedural norms; procedural restrictions provide an irreducible unifying structure for even apparently non-procedural prescriptions and normative expressions, and they are practically indispensable in our cognitive lives. (iii) These procedural epistemic norms are best analyzed in terms of the protocol (or program) constructions of dynamic logic. I defend (i) and (ii) at length and in multi-faceted ways, and I argue that they entail a set of criteria of adequacy for models of epistemic dynamics and abstract accounts of epistemic norms. I then define PLEN, the protocol-theoretic logic of epistemic norms. PLEN is a dynamic logic that analyzes epistemic rationality norms with protocol constructions interpreted over multi-graph based models of epistemic dynamics. The kernel of the overall argument of the dissertation is showing that PLEN uniquely satisfies the criteria defended; none of the familiar, rival frameworks for modeling epistemic dynamics or normative concepts are capable of satisfying these criteria to the same degree as PLEN. The overarching argument of the dissertation is thus a theory-preference argument for PLEN

COIN@AAMAS2015

COIN@AAMAS2015 is the nineteenth edition of the series and the fourteen papers included in these proceedings demonstrate the vitality of the community and will provide the grounds for a solid workshop program and what we expect will be a most enjoyable and enriching debate.Peer reviewe