Mark McKenney

A parallel plane sweep algorithm for multi-core systems

A parallel version of the plane sweep algorithm targeted towards the small number of processing cores available on commonly available multi-core systems is presented. Experimental results show that the proposed algorithm significantly out-performs the serial plane sweep on such systems.

Extracting moving regions from spatial data

We provide an algorithm that can construct a valid moving region from snapshots of a region in time. Our algorithm is robust in the sense that given valid input regions, the generated moving region will define a valid region at every instant over the given time period.

Dimension-refined topological predicates

Topological predicates, as derived from the 9-intersection model, have been widely recognized in GIS, spatial database systems, and many other geo-related disciplines. They are based on the evaluation of nine Boolean predicates checking the intersections of the boundary, interior, and exterior of a spatial object with the respective parts of another spatial object for inequality to the empty set. In this paper, we replace each Boolean predicate, which is a topological invariant, by another topological invariant. This new invariant is given as a function yielding the dimension of the respective intersection in the 9-intersection matrix, resulting in a dimension matrix. The goal of this paper is to determine the definition and semantics of all predicates that can be derived from this matrix for all combinations of spatial data types. It turns out that these dimension-based predicates are special refinements of the aforementioned topological predicates; hence, we call them dimension-refined topological predicates. We show that these predicates allow us to pose a class of more fine-grained topological queries.

Geospatial overlay computation on the GPU

General purpose computing on graphics processing units provides a relatively low cost mechanism to achieve high computational throughput on desktop computers. However, the architecture of GPUs is fundamentally different than CPUs; thus, traditional algorithms cannot simply be run on a GPU. In this paper, we develop algorithms for the line segment intersection problem and the arrangement problem for GPU architectures.

What is the foundation of evidence of human factors decisions in language design? an empirical study on programming language workshops

In recent years, the programming language design community has engaged in rigorous debate on the role of empirical evidence in the design of general purpose programming languages. Some scholars contend that the language community has failed to embrace a form of evidence that is non-controversial in other disciplines (e.g., medicine, biology, psychology, sociology, physics, chemistry), while others argue that a science of language design is unrealistic. While the discussion will likely persist for some time, we begin here a systematic evaluation of the use of empirical evidence with human users, documenting, paper-by-paper, the evidence provided for human factors decisions, beginning with 359 papers from the workshops PPIG, Plateau, and ESP. This preliminary work provides the following contributions: an analysis of the 1) overall quantity and quality of empirical evidence used in the workshops, and of the 2) overall significant challenges to reliably coding academic papers. We hope that, once complete, this long-term research project will serve as a practical catalog designers can use when evaluating the impact of a language feature on human users.

Preserving local topological relationships

Topological relationships between objects in space are of great importance in many disciplines. Recently, topological relationships have been defined for complex spatial objects. However, this definition only expresses topological relationships between complex spatial objects as a whole (global view); therefore,topological information between the individual components (local view)that compose the objects is lost. In this paper we propose a novel, hybrid model of topological relationships for composite regions that provides access to the global topological relationships as well as the local topological relationships that exist between the simple regions that are the components of the composite regions involved.

Advanced Operations for Maps in Spatial Databases

Maps are a fundamental spatial concept capable of representing and storing large amounts of information in a visual form. Map operations have been studied and rigorously defined in the literature; however, we identify a new class of map join operations which cannot be completed using existing operations. We then consider existing operations involving connectivity concepts, and extend this class of operations by defining new, more complex operations that take advantage of the connectivity properties of maps.

The CMR model of moving regions

Many natural phenomena can be nicely represented by concepts of moving regions. For example, hurricanes, rain clouds, pollution zones, etc., change shape and position over time. Current models of moving regions have proven to be difficult to translate effectively to implementation for two reasons: i) algorithms for operations, such as intersection, are difficult to implement, and ii) creating instances of moving regions from data sources is difficult. In this paper, we create a new model of moving regions at the abstract, discrete, and implementation levels that overcome the difficulties of previous models. The CMR Model aligns well with data collection techniques, can be implemented easily, and allows complex movement patterns to be easily depicted.

Deriving Topological Relationships Between Simple Regions with Holes

Topological relationships between objects in space are of great importance in many disciplines. Due to the lack of local topological information between components, i.e. faces, in the model of topological relationships between complex regions, recently, localized topological relationships have been defined for complex regions based on the relationships between simple regions with holes. However, unlike for simple regions, topological relationships between simple region with holes are not widely implemented. Therefore, in this paper, we propose an approach to derive topological relationships between simple regions with holes based on well known topological relationships between the simple regions as their components. This will allow localized topological predicates between complex regions to be implemented using only topological relationships between simple regions. Furthermore, localized topological predicates between complex regions can be used to implement topological relationships between complex regions. Therefore, this work allows topological relationships between complex regions to be implemented using only topological relationships between simple regions.

Spatial partition graphs: a graph theoretic model of maps

The notion of a map is a fundamental metaphor in spatial disciplines. However, there currently exist no adequate data models for maps that define a precise spatial data type for map geometries for use in spatial systems. In this paper, we consider a subclass of map geometries known as spatial partitions that are able to model maps containing region features. However, spatial partitions are defined using concepts such as infinite point sets that cannot be directly represented in computers. We define a graph theoretic model of spatial partitions, called spatial partition graphs, based on discrete concepts that can be directly implemented in spatial systems.