On some collusive and signaling equilibria in ascending auctions for multiple objects

We consider two ascending auctions for multiple objects: the SEAMO (simultaneous English auction for multiple objects) and the the JAMO (Japanese auction for multiple objects). We first derive a (competitive) Perfect Bayesian Equilibrium of the JAMO by exploiting the strategic equivalence between the JAMO and the Survival Auction which consists of a finite sequence of sealed-bid auctions. Then, we prove that many of the (unwanted) collusive or signaling equilibria studied in the literature in the framework of the SEAMO do not have a counterpart in the JAMO. However, it is shown that certain collusive equilibria based on retaliatory strategies do exist in both auctions.Multi-unit auctions; Ascending auctions; FCC auctions; Collusion; Retaliation

Conjunctive query answering over unrestricted OWL 2 ontologies

Conjunctive Query (CQ) answering is a primary reasoning task over knowledge bases. However, when considering expressive description logics, query answering can be computationally very expensive; reasoners for CQ answering, although heavily optimized, often sacrifice expressive power of the input ontology or completeness of the computed answers in order to achieve tractability and scalability for the problem. In this work, we present a hybrid query answering architecture that combines various services to provide a CQ answering service for OWL. Specifically, it combines scalable CQ answering services for tractable languages with a CQ answering service for a more expressive language approaching the full OWL 2. If the query can be fully answered by one of the tractable services, then that service is used, to ensure maximum performance. Otherwise, the tractable services are used to compute lower and upper bound approximations. The union of the lower bounds and the intersection of the upper bounds are then compared. If the bounds do not coincide, then the “gap” answers are checked using the “full” service. These techniques led to the development of two new systems: (i) RSAComb, an efficient implementation of a new tractable answering service for RSA (role safety acyclic) (ii) ACQuA, a reference implementation of the proposed hybrid architecture combining RSAComb, PAGOdA, and HermiT to provide a CQ answering service for OWL. Our extensive evaluation shows how the additional computational cost introduced by reasoning over a more expressive language like RSA can still provide a significant improvement compared to relying on a fully-fledged reasoner. Additionally, we show how ACQuA can reliably match the performance of PAGOdA, a state-of-the-art CQ answering system that uses a similar approach, and can significantly improve performance when PAGOdA extensively relies on the underlying fully-fledged reasoner

Domain-agnostic procedural content generation can be done declaratively

Procedural content generation is applied in the development process of many commercial games: au- tomatically generated contents are delivered to players in order to offer a constantly changing user experience and enrich the game itself. Designing algorithms for content generators can be a tedious job. The product of this work is often too domain specific and offers limited reusability and customizability. Declarative approaches to content generation, more properly defined as Declarative Content Specifica- tion (DCS) techniques, like the ones based on Answer Set Programming (ASP), promise to overcome some of these drawbacks, since they allow focusing on describing content requirements rather than programming ad-hoc generation engines. Also, DCS speed up the prototype generation techniques themselves. In turn, DCS techniques struggle to gain momentum mainly because of lack of integration with game engines. Furthermore, the promise of generality and reusability is neutralized by the burden of wiring and adapting declarative content specifications to the context of the game at hand. In this work, we report about our progress toward a general DCS module working in the Unity game engine, and integrated in an existing asset for declaratively defining AI modules. We illustrate both the design and runtime workflow of this module, and how game content developers could use it for devising their own content generation schemes. For this purpose, an example highlighting the advantages of this approach is described

Computing CQ lower-bounds over OWL 2 through approximation to RSA

Conjunctive query (CQ) answering over knowledge bases is an important reasoning task. However, with expressive ontology languages such as OWL, query answering is computationally very expensive. The PAGOdA system addresses this issue by using a tractable reasoner to compute lower and upper-bound approximations, falling back to a fully-fledged OWL reasoner only when these bounds don't coincide. The effectiveness of this approach critically depends on the quality of the approximations, and in this paper we explore a technique for computing closer approximations via RSA, an ontology language that subsumes all the OWL 2 profiles while still maintaining tractability. We present a novel approximation of OWL 2 ontologies into RSA, and an algorithm to compute a closer (than PAGOdA) lower bound approximation using the RSA combined approach. We have implemented these algorithms in a prototypical CQ answering system, and we present a preliminary evaluation of our system that shows significant performance improvements w.r.t. PAGOdA.Comment: 26 pages, 1 figur

Datalog rewriting for Guarded TGDs

We deal with the problem of fact entailment with respect to a database and a set of integrity constraints, focusing on the case of Guarded tuple-generating dependencies (GTGDs). The original approach to the problem in the literature is via forward reasoning or "chasing", where one completes the input database by adding fresh elements and facts. This completion process may be infinite, but in the case of GTGDs it is known that one can compute a point where the chase can be cut off without missing any base facts. Another approach is by forming an automaton and checking it for emptiness. Neither of these approaches scales to large input datasets. An alternative approach is to rewrite the constraints into Datalog: the Datalog rewriting can be generated in advance of any dataset and will produce the same base facts as the original constraints. It is known that Datalog rewritings always exist. But to our knowledge the approach has never been implemented. In this work we overview effective algorithms to Datalog rewriting of GTGDs. This presents work that will appear in VLDB 2022

Microsatellite panel definition to characterize Leishmania strains isolated from human samples in an italian endemic region

The Leishmaniasis affects people, domestic and wild animals in temperature, subtropical and tropical regions. The natural cycle involves phlebotominae sandfly vectors transmitting the parasite to the vertebrate host. The insects influence the epidemiology of the disease by their geographical distribution in the seasons and the specific vectorial capacity. Human Leishmania infections are increasing every year in Sicily, which represent the region with the highest endemic level of the disease in Italy. Among different approaches employed for the diagnostic the parasites isolation remains the gold standard

Post-Treatment Edema after Meningioma Radiosurgery is a Predictable Complication

Symptomatic post-treatment edema (PTE) causing seizures, focal deficits, and intracranial hypertension is a rather common complication of meningioma radiosurgery. Factors associated to the occurrence of PTE still needs to be clarified. We retrospectively analyzed our patients' data to identify factors associated with the development of symptomatic PTE. Supposed risk factors were systematically analyzed. Between July 2007 and March 2014, 245 meningiomas in 229 patients were treated by a single fraction or multisession radiosurgery (2-5 fractions) or hypofractionated stereotactic radiotherapy (6-15 fractions) using the CyberKnife system (Accuray Inc., Sunnyvale, CA) at the University Hospital of Messina, Italy. Local tumor control was achieved in 200 of 212 patients with World Health Organization (WHO) Grade I meningiomas (94%) at a mean follow-up of 62 months. Symptomatic PTE on MRI was diagnosed in 19 patients (8.3%) causing seizure (n=17, 89%), aggravating headache (n=12, 63%), or focal deficits (n=13, 68%). Four variables were found to be associated with the likelihood of edema development, including tumor volume > 4.5 mL, non-basal tumor location, tight brain/tumor interface, and atypical histology. Nonetheless, when multivariate logistic regression analysis was performed, only tumor volume and brain-tumor interface turned out to be independent predictors of PTE development. Our results suggest that the factor associated with the risk of developing PTE is associated to characteristics of meningioma rather than to the treatment modality used. Accordingly, an appropriate patient selection is the way to achieve safe treatment and long-term disease control