We establish complexities of the conjunctive query entailment problem for classes of existential rules (i.e. Tuple-Generating Dependencies or Datalog+/rules). Our contribution is twofold. First, we introduce the class of greedy bounded treewidth sets (gbts), which covers guarded rules, and their known generalizations, namely (weakly) frontier-guarded rules. We provide a generic algorithm for qu...

The field of production frontier estimation is divided between the parametric Stochastic Frontier Analysis (SFA) and the deterministic, nonparametric Data Envelopment Analysis (DEA). This paper explores an amalgam of DEA and SFA that melds a nonparametric frontier with a stochastic composite error. Our model imposes the standard SFA assumptions for the inefficiency and noise terms. The frontier...

Consider a planar Brownian motion run for finite time. The frontier or “outer boundary” of the path is the boundary of the unbounded component of the complement. Burdzy (1989) showed that the frontier has infinite length. We improve this by showing that the Hausdorff dimension of the frontier is strictly greater than 1. (It has been conjectured that the Brownian frontier has dimension 4/3, but ...

This paper examines several extensions of the stochastic frontier that account for unmeasured heterogeneity as well as firm inefficiency. The fixed effects model is extended to the stochastic frontier model using results that specifically employ its nonlinear specification. Based on Monte Carlo results, we find that the incidental parameters problem operates on the coefficient estimates in the ...

The idea of the frontier reflects a uniquely colonial view of a place and process of encounter between colonising people, indigenous inhabitants, and natural landscapes.[1] Within this colonial context, the idea of the frontier has been variously developed through history by natural and social scientists, popular historians, artists, writers, and government officials. This volume draws together...

Frontier-based exploration is the most common approach to exploration, a fundamental problem in robotics. In frontierbased exploration, robots explore by repeatedly detecting (and moving towards) frontiers, the segments which separate the known regions from those unknown. A frontier detection sub-process examines map and/or sensor readings to identify frontiers for exploration. However, most fr...

We consider the case of production units arranged into a number of groups. All units within a group choose output-input combinations from the same production possibilities set, which is represented by a stochastic frontier model. The metafrontier is the envelope (over groups) of the group-specific frontiers. We are interested in the unit’s inefficiency relative to its group-specific frontier, b...

The current study aims to explore the connections between business environments and firms' competitive priorities, which establish the basis for manufacturing strategy. This study explicitly considers the effects of asset and operating frontiers, as well as trade-offs across competitive priorities, a topic which has not been thoroughly studied by prior research. We collected data from 434 Chine...

Exploring an unknown environment with multiple robots requires an efficient coordination method to minimize the total duration. A standard method to discover new areas is to assign frontiers (boundaries between unexplored and explored accessible areas) to robots. In this context, the frontier allocation method is paramount. This paper introduces a decentralized and computationally efficient fro...

due to agriculture is a risky activity and risk models is important in order to analyze the behavior of farmers, hence, in this study, the factors affecting risk-taking and risk aversion is the region grape growers. data analysis was performed by using stochastic frontier. data gathered by questionnaires at three counties of zabol, hirmand and zahak at 265 grape farmers in crop year of 2011-201...