We present a general approach for introducing specificity information into nonmonotonic theories. Historically, many approaches to nonmonotonic reasoning, including default logic, circumscription, and autoepistemic logic, do not provide an account of specificity, and so fail to enforce specificity among default sentences. In our approach, a default theory is initially given as a set of strict a...

Nonmonotonic reasoning is succesfully formalized by the class of default logics. In this paper we introduce an axiomatic system for credulous reasoning in rational default logic. Based on classical sequent calculus and anti-sequent calculus, an abstract characterization of credulous nonmonotonic default inference in this variant of default logic is presented.

Default configuration of various software applications often neglects security objectives. We tested the default configuration of TLS in dozen web and application servers. The results show that “secure by default” principle should be adopted more broadly by developers and package maintainers. In addition, system administrators cannot rely blindly on default security options.

Default unification has been used in several linguistic applications. Most of them have utilized defaults at a meta-level, as part of an extended description language. We propose that allowing default unification to be a fully integrated part of a typed feature structure system requires default unification to be a binary, order independent function, so that it acquires the perspicuity and decla...

Our paper provides a complete characterization of leverage and default in binomial economies with financial assets serving as collateral. Our Binomial No-Default Theorem states that any equilibrium is equivalent (in real allocations and prices) to another equilibrium in which there is no default. Thus actual default is irrelevant, though the potential for default drives the equilibrium and limi...

Reiter’s default logic formalizes nonmonotonic reasoning using default assumptions. The semantics of a given instance of default logic is based on a fixpoint equation defining an extension. Three different reasoning problems arise in the context of default logic, namely the existence of an extension, the presence of a given formula in an extension, and the occurrence of a formula in all extensi...

Our paper provides a complete characterization of leverage and default in binomial economies with financial assets serving as collateral. Our Binomial No-Default Theorem states that any equilibrium is equivalent (in real allocations and prices) to another equilibrium in which there is no default. Thus actual default is irrelevant, though the potential for default drives the equilibrium and limi...

We study the implied default distributions for the iTraxx-CJ tranches by means of the Principle of Maximum Entropy. The profiles are quite different from those of some popular probabilistic models. We show how to analyze the correlation structures, the conditional default probabilities pi,j and conditional default correlations ρi,j . Here the subscript i,j means that the default probability and...

We present a development of the theory of default information structures, combining ideas from domain theory with ideas from non-monotonic logic. Conceptually, our treatment is distinguished from standard default logic in that we view default structures as generating models rather than theories. Reiter's default rules are viewed as non-deterministic algorithms for generating preferred partial m...

We examine the default probabilities predicted by “structural” models of risky corporate debt. Two types of models are examined: those with “exogenous” default boundaries, typified by Longstaff and Schwartz (1995); and those with “endogenous” default boundaries, typified by Leland and Toft (1996). We focus on default probabilities rather than credit spreads because (i) they are not affected by ...