Model Checking Social Network Models

A social network service is a platform to build social relations among people sharing similar interests and activities. The underlying structure of a social networks service is the social graph, where nodes represent users and the arcs represent the users' social links and other kind of connections. One important concern in social networks is privacy: what others are (not) allowed to know about us. The "logic of knowledge" (epistemic logic) is thus a good formalism to define, and reason about, privacy policies. In this paper we consider the problem of verifying knowledge properties over social network models (SNMs), that is social graphs enriched with knowledge bases containing the information that the users know. More concretely, our contributions are: i) We prove that the model checking problem for epistemic properties over SNMs is decidable; ii) We prove that a number of properties of knowledge that are sound w.r.t. Kripke models are also sound w.r.t. SNMs; iii) We give a satisfaction-preserving encoding of SNMs into canonical Kripke models, and we also characterise which Kripke models may be translated into SNMs; iv) We show that, for SNMs, the model checking problem is cheaper than the one based on standard Kripke models. Finally, we have developed a proof-of-concept implementation of the model-checking algorithm for SNMs.Comment: In Proceedings GandALF 2017, arXiv:1709.0176

Guanxi and business environment in china: an innovative network as a process of knowledge-based economy

Guanxi is a specific part of Chinese business environment. Since the openness of China, it seems that a contradiction appears between the constraints of corporate governance and the cultural and traditional behaviour in business. Most of west analyses consider that Guanxi is only a form of corruption and therefore it should be fight it out. The originality of our work is to frame these questions in the context of recent concepts such as communities of practice and epistemic communities. Based on these concepts, we consider that the firm can be analysed from a dual perspective: cognitive and organisational. The first one belongs to the guanxi logic and the second one to the corporate governance. According to these framework, we point out the fact that guanxi provides an innovative network in order to diffuse and enhance knowledge.Guanxi, corporate governance, communities, knowledge, network

Logiques pour les réseaux sociaux : annonces asynchrones dans des structures orthogonales

Cette thèse a deux objets d'étude principaux. D'une part, nous proposons et étudions des modèles de transmission et de réception asynchrones de messages. Pour cela, nous nous plaçons dans le cadre des logiques épistémiques dynamiques - un sous-domaine de la logique modale qui formalise les états épistémiques d'un agent (i.e. ce que l'agent sait) et qui caractérise la façon dont ces états évoluent en différentes circonstances. La plus connue des logiques épistémiques dynamiques est la logique des annonces publiques (Plaza, 1989) - une logique dynamique qui considère comme action de base l'action d'effectuer une annonce publique. Dans un système multi-agent, il est dans la connaissance commune des agents que les messages sont reçus par tous les agents au même instant. Dans le chapitre principal de la thèse, nous proposons un modèle d'annonces asynchrones dans lequel les agents peuvent recevoir les annonces à différents instants tout en ignorant si les autres agents ont également reçu ces annonces. D'autre part, nous étudions une classe de structures relationnelles qui apparaissent assez souvent en logique modale : la classe des cadres orthogonaux. Les cadres orthogonaux sont des structures birelationnelles dans lesquelles deux composantes connexes arbitraires déterminées par les deux relations ont au plus un élément en commun. Pour différentes restrictions de la classe des cadres orthogonaux, nous proposons des axiomatisations correctes et complètes des ensembles de formules valides que ces restrictions déterminent et nous proposons quelques résultats de décidabilité de ces ensembles. Pour illustrer l'ubiquité des cadres orthogonaux, nous proposons des exemples de classes de modèles pour les logiques modales qui sont basées sur eux et nous montrons comment les résultats de la thèse peuvent être utilisés pour étudier ces classes du point de vue de leur orthogonalité. Enfin, nous combinons les deux parties précédentes dans le contexte de la logique épistémique sociale (Seligman et al., 2011). Il s'agit d'une logique développée pour l'étude des états épistémiques des agents dans un réseau social. Nous proposons différentes extensions dynamiques de cette logique et, en particulier, nous modélisons la transmission d'annonces asynchrones dans un réseau social.This thesis has two main objects of study, closely related to each other. On the one hand, we provide and study models for asynchronous transmission and reception of messages. To do this, we utilize the framework of Dynamic Epistemic Logic, a branch of Modal Logic which studies the epistemic state of an agent (i.e. what they know) and how this state changes under several circumstances. One of the better known dynamic epistemic logics is Public Announcement Logic (Plaza, 1989), a logic which allows for a notion of recieving a message. In a multi-agent system, this message is received by all agents at the same time, and they all know that the others have received it. In the main chapter of this thesis, we provide a framework for asynchronous announcements, in which the agents might receive the message at different times and be uncertain whether others know the information contained within it. On the other hand, we study a class of relational structures for modal logics which show up quite often in different areas of the literature: this is the class of orthogonal frames. Orthogonal frames are bi-relational structures wherein two distinct points cannot be connected by both relations at the same time. We give a sound and complete logic of orthogonal frames under different restrictions, and we provide decidability results. To illustrate the ubiquity of these structures, we provide multiple examples of frameworks for modal logics which are based on orthogonal frames, and we use some of the results obtained earlier to show how one can further the study of these structures by focusing on their orthogonality. To finish up, we combine the two areas of study, by taking as a case study the orthogonal framework of Social Epistemic Logic (Seligman et al., 2011). This is a framework for studying the epistemic state of agents in a social network. We provide different dynamic extensions, and in particular we give a way to model the transmission of announcements asynchronously in a social networ

Agent-update Models

In dynamic epistemic logic (Van Ditmarsch et al., 2008) it is customary to use an action frame (Baltag and Moss, 2004; Baltag et al., 1998) to describe different views of a single action. In this article, action frames are extended to add or remove agents, we call these agent-update frames. This can be done selectively so that only some specified agents get information of the update, which can be used to model several interesting examples such as private update and deception, studied earlier by Baltag and Moss (2004); Sakama (2015); Van Ditmarsch et al. (2012). The product update of a Kripke model by an action frame is an abbreviated way of describing the transformed Kripke model which is the result of performing the action. This is substantially extended to a sum-product update of a Kripke model by an agent-update frame in the new setting. These ideas are applied to an AI problem of modelling a story. We show that dynamic epistemic logics, with update modalities now based on agent-update frames, continue to have sound and complete proof systems. Decision procedures for model checking and satisfiability have expected complexity. A sublanguage is shown to have polynomial space algorithms