# Xavier Parent's research while affiliated with TU Wien and other places

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## Publications (51)

A shallow semantical embedding of a dyadic deontic logic by Carmo and Jones in classical higher-order logic is presented. The embedding is proven sound and complete, that is, faithful. This result provides the theoretical foundation for the implementation and automation of dyadic deontic logic within off-the-shelf higher-order theorem provers and p...

Inspired by Kelsen’s view that norms establish causal-like connections between facts and sanctions, we develop a deontic logic in which a proposition is obligatory iff its complement causes a violation. We provide a logic for normative causality, define non-contextual and contextual notions of illicit and duty, and show that the logic of such dutie...

A shallow semantical embedding of a dyadic deontic logic by Carmo and Jones in classical higher-order logic is presented. The embedding is proven sound and complete, that is, faithful. This result provides the theoretical foundation for the implementation and automation of dyadic deontic logic within o�-the-shelf higher- order theorem provers and p...

Introduction to the Special Issue on Logic Rules and Reasoning: Selected Papers from the 2nd International Joint Conference on Rules and Reasoning (RuleML+RR 2018) - CHRISTOPH BENZMÜLLER, XAVIER PARENT, FRANCESCO RICCA

The LogiKEy workbench and dataset for ethical and legal reasoning is presented. This workbench simultaneously supports development, experimentation, assessment and deployment of formal logics and ethical and legal theories at different conceptual layers. More concretely, it comprises, in form of a data set (Isabelle/HOL theory files), formal encodi...

A shallow semantical embedding of a dyadic deontic logic by Carmo and Jones in classical higher-order logic is presented. The embedding is proven sound and complete, that is, faithful. This result provides the theoretical foundation for the implementation and automation of dyadic deontic logic within o-the-shelf higher-order theorem provers and pro...

Deontic logic is the logic of normative concepts such as obligations, permissions, and rights, and it is used in knowledge representation to formalize ethical and legal reasoning. Norms can be conflicting and subject to exceptions, they can originate from various authorities, and they can specify ideal as well as sub-ideal situations and actions. A...

A framework and methodology—termed LogiKEy—for the design and engineering of ethical reasoners, normative theories and deontic logics is presented. The overall motivation is the development of suitable means for the control and governance of intelligent autonomous systems. LogiKEy's unifying formal framework is based on semantical embeddings of deo...

A framework and methodology---termed LogiKEy---for the design and engineering of ethical reasoners, normative theories and deontic logics is presented. The overall motivation is the development of suitable means for the control and governance of intelligent autonomous systems. LogiKEy's unifying formal framework is based on semantical embeddings of...

A shallow semantical embedding of Input/output logic in classical higher-order logic is presented, and shown to be faithful (sound and complete). This embedding has been implemented in Isabelle/HOL, a proof assistant tool. It is applied to a well-known example in moral philosophy, the example of moral luck.

We devise a shallow semantical embedding of Åqvist's dyadic deontic logic E in classical higher-order logic. This embedding is shown to be faithful, viz. sound and complete. This embedding is also encoded in Isabelle/HOL, which turns this system into a proof assistant for deontic logic reasoning. The experiments with this environment provide eviden...

This article reports on the Second International Joint Conference on Rules and Reasoning (RuleML+RR 2018), which was held at the University of Luxembourg from September 18–21, 2018.

A shallow semantical embedding of a dyadic deontic logic by Carmo and Jones in classical higher-order logic is presented. This embedding is proven sound and complete, that is, faithful. The work presented here provides the theoretical foundation for the implementation and automation of dyadic deontic logic within o-the-shelf higher-order theorem pr...

A flexible infrastructure for the automation of deontic and normative reasoning is presented. Our motivation is the development, study and provision of legal and moral reasoning competencies in future intelligent machines. Since there is no consensus on the “best” deontic logic formalisms and since the answer may be application specific, a flexible...

A flexible infrastructure for normative reasoning is outlined. A small-scale demonstrator version of the envisioned system has been implemented in the proof assistant Isabelle/HOL by utilising the first authors universal logical reasoning approach based on shallow semantical embeddings in meta-logic HOL. The need for such a flexible reasoning infra...

A semantical embedding of input/output logic in classical higher-order logic is presented. This embedding enables the mechanisation and automation of reasoning tasks in input/output logic with off-the-shelf higher-order theorem provers and proof assistants. The key idea for the solution presented here results from the analysis of an inaccurate prev...

A shallow semantical embedding of a dyadic deontic logic by Carmo and Jones in classical higher-order logic is presented. This embedding is proven sound and complete, that is, faithful. The work presented here provides the theoretical foundation for the implementation and automation of dyadic deontic logic within off-the-shelf higher-order theorem...

The ideal worlds of a possible worlds semantics may satisfy both a primary obligation and an associated secondary obligation, for example the obligation to keep a promise and the obligation to apologise for not keeping it. This is known as the pragmatic oddity introduced by Prakken and Sergot. We argue that an adequate treatment of the pragmatic od...

It is shown that I/O logic can be based on intuitionistic logic instead of classical logic. More specifically, it is established that, when going intuitionistic, a representation theorem is still available for three of the four (unconstrained) original I/O operations. The trick is to see a maximal consistent set as a saturated one. The axiomatic ch...

Makinson and van der Torre [13] introduce a number of input/output (I/O) logics to reason about conditional norms. The key idea is to make obligations relative to a given set of conditional norms. The meaning of the normative concepts is, then, given in terms of a set of procedures yielding outputs for inputs. Using the same methodology, Stolpe[19,...

This paper tackles an open problem posed by Aqvist. It is the problem of whether his dyadic deontic systems E and F are complete with respect to their intended Hanssonian preference-based semantics. It is known that there are two different ways of interpreting what it means for a world to be best or top-ranked among alternatives. This can be unders...

This paper reports completeness results for dyadic deontic logics in the tradition of Hansson’s systems. There are two ways to understand the core notion of best antecedent-worlds, which underpins such systems. One is in terms of maximality, and the other in terms of optimality. Depending on the choice being made, one gets different evaluation rule...

Deontic logic is the logic of obligation and permission. In the literature it has mainly been studied in terms of a list of problems and that is the way we chose to present it in this section. There are three main categories of problems. The first category is concerned with the nature of norms. The second category concerns phenomena of conflict, vi...

The paper discusses the views held by M. Sergot and H. Prakken [in: D. Nute (ed.), Defeasible deontic logic. Dordrecht: Kluwer Academic Publishers. Synth. Libr. 263, 223–262 (1997; Zbl 0913.03009)] on the import, or non-import, of the identity principle for conditional obligation within a preference-based semantics. This is the principle ◯(A/A). Th...

The aim of the paper is to bring to the realm of game theory the well-known deontic notion of contrary-to-duty (CTD) obligation, so far not investigated in relation to optimality of strategic decisions. We maintain that, under a game-theoretical semantics, CTDs are well-suited to treat sub-ideal decisions. We also argue that, in a wide class of int...

The paper discusses the views held by Sergot and Prakken [22] on the import, or non-import, of the identity principle for conditional obligation within a preference-based semantics. This is the principle $\bigcirc (A/A)$ . The key point is to understand and appreciate what unconditional obligations the principle allows us to detach, and from what p...

The aim of this paper is to strengthen the point made by Horty about the relationship between reason holism and moral particularism.
In the literature prima facie obligations have been considered as the only source of reason holism. I strengthen Horty’s point
in two ways. First, I show that contrary-to-duties provide another independent support for...

This paper offers a two dimensional variation of Standard Deontic Logic SDL, which we call 2SDL. Using 2SDL we can show that we can overcome many of the difficulties that SDL has in representing linguistic sets of Contrary-to-Duties (known as paradoxes) including the Chisholm, Ross, Good Samaritan
and Forrester paradoxes. We note that many dimensio...

The aim of this paper is to strengthen the point made by Horty about the relationship between reason holism and moral particularism.
In the literature prima facie obligations have been considered as the only source of reason holism. I strengthen Horty’s point
in two ways. First, I show that contrary-to-duties provide another independent support for...

The main contribution of this paper is a (strong) completeness result for an axiomatization of Hansson [13]'s deontic system DSDL2, whose semantics involves a non-necessarily transitive betterness relation. Reference is made to
a deductive system put forth by Åqvist [2, 3].

Aqvist's dyadic deontic logic G, which aims at providing an axiomatic characterization of Hansson's seminal system DSDL3 for con- ditional obligation, is shown to be strongly complete with respect to its intended modelling.

This paper is a preliminary investigation into the application of the formal-logical theory of normative positions to the characterisation of normative- informational positions, pertaining to rules that are meant to regulate the supply of information. First, we present the proposed framework. Next, we identify the kinds of nuances and distinctions...

This article aims to provide foundations for a new approach to Agent Communication Languages (ACLs). First, we present the
theory of signalling acts. In contrast to current approaches to communication, this account is neither intention-based nor
commitment-based, but convention-based. Next, we explore ways of embedding that theory within an account...

The paper makes two main contributions: (1) It presents experiences from using the CORAS language for security threat modelling
to specify legal risk scenarios. These experiences are summarised in the form of requirements to a more expressive language
providing specific support for the legal domain. (2) Its second main contribution is to present id...

This article aims to provide foundations for a new approach to Agent Communication Languages (ACLs). First, we present the theory of sig-nalling acts. In contrast to current approaches to communication, this ac-count is neither intention-based nor committment-based, but convention-based. Next, we explore ways of embedding that theory within an acco...

This article aims to provide foundations for a new approach to Agent Communication Languages (ACLs). First, we outline the theory of signalling acts. In contrast to current approaches to communication, this account is neither intention-based nor commitment-based, but convention-based. Next, we outline one way of embedding that theory within an acco...

This paper discusses the relation between deontic logic and the study of conversa- tional interactions. Special attention is given to the notion of remedial interchange as analysed by sociologists and linguistic pragmaticians. This notion is close to the one of contrary-to-duty (reparational) obligation, which deontic logicians have been studying i...

We rst analyse the future-orientated account of conditional obligation as put forth by David Makinson. We show that the introduction of the futurity dimension is not indispensable in the elimination of the identity principle. This leads us to a more general observation. Most systems of dyadic deontic logic either accept both the identity principle...

## Citations

... The dyadic deontic operator is represented by {$$obl} (short for obligatory). An embedding of the above DDL is studied in [7,5] Note that the name $modal of modal logics and that of its connective names are given by TPTP defined names (starting with a single dollar sign) since it is the first non-classical logic standardized by the TPTP [21,36]. All further logics are LET-specific logic representations that have not (yet) been included in the collection of TPTP curated NCLs; following the TPTP naming convention, their identifiers hence start with two dollar signs (system defined names). ...

... Prior work by Benzmüller et. al. [12,10] implements DDL in Isabelle. I add the Formula of Universal Law as an axiom to their library. ...

... An entirely different approach to tool support is taken with the LogiKEy [6] workbench that codes legal reasoning in the Isabelle interactive proof assistant, paving the way for a very expressive formalism. In contrast, we have opted for a DSL with fully automated proofs which are provided by SMT respectively ASP solvers. ...

Reference: Automating Defeasible Reasoning in Law

... Prior work by Benzmüller et. al. [12,10] implements DDL in Isabelle. I add the Formula of Universal Law as an axiom to their library. ...

... Nancy also assumes that constants denote flexibly, while employing a more sophisticated logic, e.g., the deontic system E [41,42]. In contrast to SDL this logic is suitably extended to deal with norm violations (e.g., contrary-to-duty reasoning) so that they do not result in inconsistencies. ...

... Lastly, the scarcity of legal reasoning software prevents the utilization of such formalizations, even if proven correct. One can mention here the engines for defeasible logics [9], Higher-order logics [3] and Deontic logics with contrary-to-duty obligations [12]. ...

... Decision procedures exist for some logics, like the KED theorem prover for Standard Deontic Logic [4], and the decision procedures in [5]. There are even fewer implemented tools, such as MCMAS, the OBDD-based checker in [29] for the logic of [37], and the implementation of dyadic deontic logic in Isabelle/HOL in [8]. A proof system for a simplified version of DAU has been developed in [3,33] to determine whether certain obligations follow from others (a 'trusted base'). ...

... The semantic embeddings approach gives us two important benefits: (i) we can reuse existing automated theorem proving technology for HOL and apply it for automated reasoning in non-classical logics (e.g. free [11], modal [10], intu- itionistic [9] and deontic [8] logics); and (ii) the logic of formalization becomes another degree of freedom in the development of a logical theory and thus can be fine-tuned dynamically by adding or removing axioms (which are encoded using HOL as a meta-language). ...

... input/output logic [114] and dyadic deontic logic [115]. First results in this application direction are promising [116,117,118,119]. ...

... I/O logic [64]: The main challenge comes from the fact that the framework does not have a truth-functional semantics, but an operational one. First experiments with the SSE of the I/O-operator out 1 (called simple-minded) and out 2 (called basic) in Isabelle/HOL have been presented in the literature [10,73]. ...