Query Containment for Highly Expressive Datalog Fragments

The containment problem of Datalog queries is well known to be undecidable. There are, however, several Datalog fragments for which containment is known to be decidable, most notably monadic Datalog and several "regular" query languages on graphs. Monadically Defined Queries (MQs) have been introduced recently as a joint generalization of these query languages. In this paper, we study a wide range of Datalog fragments with decidable query containment and determine exact complexity results for this problem. We generalize MQs to (Frontier-)Guarded Queries (GQs), and show that the containment problem is 3ExpTime-complete in either case, even if we allow arbitrary Datalog in the sub-query. If we focus on graph query languages, i.e., fragments of linear Datalog, then this complexity is reduced to 2ExpSpace. We also consider nested queries, which gain further expressivity by using predicates that are defined by inner queries. We show that nesting leads to an exponentially increasing hierarchy for the complexity of query containment, both in the linear and in the general case. Our results settle open problems for (nested) MQs, and they paint a comprehensive picture of the state of the art in Datalog query containment.Comment: 20 page

A Polynomial Translation of pi-calculus FCPs to Safe Petri Nets

We develop a polynomial translation from finite control pi-calculus processes to safe low-level Petri nets. To our knowledge, this is the first such translation. It is natural in that there is a close correspondence between the control flows, enjoys a bisimulation result, and is suitable for practical model checking.Comment: To appear in special issue on best papers of CONCUR'12 of Logical Methods in Computer Scienc

Peripheral diversity: transfers versus public goods

This paper advances the hypothesis that in societies that suffer from ethnolinguistic center-periphery tension it is harder to agree on public goods than on transfers. After micro-founding a new peripheral diversity index, it puts forth a simple theory in which the cost of public goods increases with peripheral ethnolinguistic diversity and tax compliance decreases with overall ethnolinguistic diversity. It then empirically explores the relation between public goods provision, transfers, peripheral diversity and overall diversity. Consistent with the theory, we find that higher levels of peripheral diversity are associated with less provision of public goods, but more transfers, whereas higher levels of overall diversity have a negative association with transfers. Public goods and transfers are therefore substitutes in their reaction to a change in peripheral diversity.I. Ortuño-Ortín acknowledges the financial support of the Spanish Ministry of Science and Innovation, Project ECO-2013-42710-P, and S. Weber wishes to acknowledge the support of the Ministry of Education and Science of the Russian Federation, Grant No. 14.U04.31.0002, administered through the NES CSDSI

Nonuniversality of indirect CP asymmetries in D→ππ,KKD \to \pi\pi, KK decays

We point out that, if the direct CP asymmetries in the $D \to \pi^+ \pi^-$ and $D \to K^+ K^-$ decays are unequal, the indirect CP asymmetries as measured in these modes are necessarily unequal. This nonuniversality of indirect CP asymmetries can be significant with the right amount of new physics contributions, a scenario that may be fine-tuned, but is still viable. A model-independent fit to the current data allows different indirect CP asymmetries in the above two decays. This could even be contributing to the apparent tension between the difference CP asymmetries $\Delta A_{\rm CP}$ measured through the pion-tagged and muon-tagged data samples at the LHCb. This also implies that the measurements of $A_\Gamma$ and $y_{\rm CP}$ in the $\pi^+ \pi^-$ and $K^+ K^-$ decay modes can be different, and averaging over these two modes should be avoided. In any case, the complete analysis of CP violation measurements in the $D$ meson sector needs to take into account the possibility of different indirect CP asymmetries in the $\pi^+\pi^-$ and $K^+ K^-$ channels.Comment: 23 pages, 14 Postscript figures, matches published versio

The good, the bad and the ugly in the melting pot: the challenges of Nigerianising diversity management

Taking a clue from the aftermaths of colonisation and the need to manage an 'unholy marriage' created by the British colonial masters, the review paper examines the peculiar challenges of managing Nigeria's unique diversity in the public sector through the critical lens of the Federal Character Principle (FCP) with specific focus on how this invented model of diversity management ended up creating more serious problems than it was meant to solve in the Nigerian public administration. The paper is essentially a review, and it relies on previous studies and real-world evidence on the subject. The paper systematically traces the evolution of diversity management in Nigeria’s public administration through the critical lens of the Federal Character Principle (FCP) with specific focus on how problematic it is to management Nigeria's unique diversity with more serious problems being created by the FCP application in the public sector. The paper reveals that the constitutional provisions of the ‘Federal Character Principle’ (FCP) ended up creating more problems than it set out to solve, reflecting in the 'melting pot' allegory. It reveals how problematic it is to manage the country's diversity, and highlights some of the problems created by the FCP. The review makes a case for an urgent need to intensify empirical research on the subject in order to fashion out a better way of managing Nigeria's diversity in the public sector. One major limitation of this paper is rooted lack of empirical research such as survey to further explore the topic. However, some real-life examples and cases were provided were drawn on the phenomenon. Thus, a call for more systematic and empirical research is made. The implication of the finding is that the model for managing workforce diversity especially in the Nigerian public sector (not limited to the public administration) must be ‘Nigerianised’ such that the unique socio-cultural realities of the Nigeria's society as well as benefits accrued to diversity can be fully explored in driving the growth of the country and survival of the 'unity-in-diversity' goal. The paper will benefit the government, relevant stakeholders, and the Nigerian society at large. It offers some useful insights into public administration. It stimulates an interest to conduct further research on diversity management with a view to producing some useful findings that could lead to a better management of diversity in the country

Classical Cryptographic Protocols in a Quantum World

Cryptographic protocols, such as protocols for secure function evaluation (SFE), have played a crucial role in the development of modern cryptography. The extensive theory of these protocols, however, deals almost exclusively with classical attackers. If we accept that quantum information processing is the most realistic model of physically feasible computation, then we must ask: what classical protocols remain secure against quantum attackers? Our main contribution is showing the existence of classical two-party protocols for the secure evaluation of any polynomial-time function under reasonable computational assumptions (for example, it suffices that the learning with errors problem be hard for quantum polynomial time). Our result shows that the basic two-party feasibility picture from classical cryptography remains unchanged in a quantum world.Comment: Full version of an old paper in Crypto'11. Invited to IJQI. This is authors' copy with different formattin