Category Archives: Papers

Hierarchical Prism Trees for Scalable Time Geographic Analysis

We have a full paper accepted for GIScience 2016:

Carson J. Q. Farmer and Carsten Keßler (2016) Hierarchical Prism Trees for Scalable Time Geographic Analysis. Full paper accepted for GIScience 2016, September 27–30, 2016, Montreal, Canada.

Abstract: As location-aware applications and location-based services continue to increase in popularity, data sources describing a range of dynamic processes occurring in near real-time over multiple spatial and temporal scales are becoming the norm. At the same time, existing frame- works useful for understanding these dynamic spatio-temporal data, such as time geography, are unable to scale to the high volume, velocity, and variety of these emerging data sources. In this paper, we introduce a com- putational framework that turns time geography into a scalable analysis tool that can handle large and rapidly changing datasets. The Hierar- chical Prism Tree (HPT) is a dynamic data structure for fast queries on spatio-temporal objects based on time geographic principles and theories, which takes advantage of recent advances in moving object databases and computer graphics. We demonstrate the utility of our proposed HPT us- ing two common time geography tasks (finding similar trajectories and mapping potential space-time interactions), taking advantage of open data on space-time vehicle emissions from the EnviroCar platform.

New Paper in Journal of Web Semantics

Carsten Keßler and Carson J. Q. Farmer (2015) Querying and integrating spatial–temporal information on the Web of Data via time geography. Journal of Web Semantics, in press. DOI: 10.1016/j.websem.2015.09.005

Abstract: The Web of Data is a rapidly growing collection of datasets from a wide range of domains, many of which have spatial–temporal aspects. Hägerstrand’s time geography has proven useful for thinking about and understanding the movements and spatial–temporal constraints of humans. In this paper, we explore time geography as a means of querying and integrating multiple spatial–temporal data sources. We formalize the concept of the space–time prism as an ontology design pattern to use as a framework for understanding and representing constraints and interactions between entities in space and time. We build on a formalization of space–time prisms and apply it in the context of the Web of Data, making it usable across multiple domains and topics. We demonstrate the utility of this approach through two use cases from the domains of environmental monitoring and cultural heritage, showing how space–time prisms enable spatial–temporal and semantic reasoning directly on distributed data sources.

Papers accepted for AGILE and AAAI Spring Symposium

I have two new papers accepted, one for AGILE 2015 in Lisbon, and one for the AAAI Spring Symposium 2015 on Structured Data for Humanitarian Technologies in Stanford. The latter was a collaboration with Tim Clark and Hemant Purohit. Find the preliminary citations below; click the title for a preprint PDF:

  • Carsten Keßler (forthcoming 2015) Central Places in Wikipedia. Accepted for the 18th AGILE Conference on Geographic Information Science: Geographic information Science as an enabler of smarter cities and communities. June 9–12, 2015. Lisbon, Portugal

Abstract Central Place Theory explains the number and locations of cities, towns, and villages based on principles of market areas, transportation, and socio-political interactions between settlements. It assumes a hexagonal segmentation of space, where every central place is surrounded by six lower-order settlements in its range, to which it caters its goods and services. In reality, this ideal hexagonal model is often skewed based on varying popu- lation densities, locations of natural features and resources, and other factors. In this paper, we propose an approach that extracts the structure around a central place and its range from the link structure on the Web. Using a corpus of georeferenced documents from the English language edition of Wikipedia, we combine weighted links between places and semantic annotations to compute the convex hull of a central place, marking its range. We compare the results obtained to the structures predicted by Central Place Theory, demonstrating that the Web and its hyperlink structure can indeed be used to infer spatial structures in the real world. We demonstrate our approach for the four largest metropolitan areas in the United States, namely New York City, Los Angeles, Chicago, and Houston.

Abstract Given the rise of humanitarian crises in the recent years, and adoption of multiple data sharing platforms in offline and online environments, it is increasingly challenging to collect, organize, clean, integrate, and analyze data in the humanitarian domain. On the other side, computer science has built efficient technologies to store, integrate and analyze structured data, however, their role in the humanitarian domain is yet to be shown. We present a case of how structured data technology, specifically Linked Open Data from the Semantic Web area, can be applied for information interoperability in the humanitarian domain. We present the domain-specific challenges, description of the technology adoption via an example of real world adoption of the Humanitarian Exchange Language (HXL) ontology, and describe the lessons from that to build the case of why, how and which components of technologies can be effective for information organization and interoperability in the humanitarian domain.

GeoPrivacy’14 Proceedings

The proceedings of our 1st ACM SIGSPATIAL International Workshop on Privacy in Geographic Information Collection and Analysis have been published online:

We had a great workshop last week, with interesting discussions that showed how pressing the issue of privacy in geographic information is, and that there is still a lot to do. We are already planning some follow-up activities, so stay posted.

New paper out in JMIR Medical Informatics

We have new paper out in JMIR Medical Informatics, an open access journal that focusses on clinical informatics, big data in health and health care, decision support for health professionals, electronic health records, and ehealth infrastructures:

Binyam Tilahun, Tomi Kauppinen, Carsten Keßler and Fleur Fritz (2014) Design and Development of a Linked Open Data-Based Health Information Representation and Visualization System: Potentials and Preliminary Evaluation. JMIR Medical Informatics 2(2):e31

Here’s the abstract:

Background: Healthcare organizations around the world are challenged by pressures to reduce cost, improve coordination and outcome, and provide more with less. This requires effective planning and evidence-based practice by generating important information from available data. Thus, flexible and user-friendly ways to represent, query, and visualize health data becomes increasingly important. International organizations such as the World Health Organization (WHO) regularly publish vital data on priority health topics that can be utilized for public health policy and health service development. However, the data in most portals is displayed in either Excel or PDF formats, which makes information discovery and reuse difficult. Linked Open Data (LOD)—a new Semantic Web set of best practice of standards to publish and link heterogeneous data—can be applied to the representation and management of public level health data to alleviate such challenges. However, the technologies behind building LOD systems and their effectiveness for health data are yet to be assessed.

Objective: The objective of this study is to evaluate whether Linked Data technologies are potential options for health information representation, visualization, and retrieval systems development and to identify the available tools and methodologies to build Linked Data-based health information systems.

Methods: We used the Resource Description Framework (RDF) for data representation, Fuseki triple store for data storage, and Sgvizler for information visualization. Additionally, we integrated SPARQL query interface for interacting with the data. We primarily use the WHO health observatory dataset to test the system. All the data were represented using RDF and interlinked with other related datasets on the Web of Data using Silk—a link discovery framework for Web of Data. A preliminary usability assessment was conducted following the System Usability Scale (SUS) method.

Results: We developed an LOD-based health information representation, querying, and visualization system by using Linked Data tools. We imported more than 20,000 HIV-related data elements on mortality, prevalence, incidence, and related variables, which are freely available from the WHO global health observatory database. Additionally, we automatically linked 5312 data elements from DBpedia, Bio2RDF, and LinkedCT using the Silk framework. The system users can retrieve and visualize health information according to their interests. For users who are not familiar with SPARQL queries, we integrated a Linked Data search engine interface to search and browse the data. We used the system to represent and store the data, facilitating flexible queries and different kinds of visualizations. The preliminary user evaluation score by public health data managers and users was 82 on the SUS usability measurement scale. The need to write queries in the interface was the main reported difficulty of LOD-based systems to the end user.

Conclusions: The system introduced in this article shows that current LOD technologies are a promising alternative to represent heterogeneous health data in a flexible and reusable manner so that they can serve intelligent queries, and ultimately support decision-making. However, the development of advanced text-based search engines is necessary to increase its usability especially for nontechnical users. Further research with large datasets is recommended in the future to unfold the potential of Linked Data and Semantic Web for future health information systems development.

Democratizing Mobile App Development for Disaster Management →

The first papers pop up that make use of our Humanitarian eXchange Language (HXL). This one, presented at Semantic Cities 2013 workshop, is by a group at MIT. Here’s the abstract:

Smartphones are being used for a wide range of activities including messaging, social networking, calendar and contact management as well as location and context-aware applications. The ubiquity of handheld computing technology has been found to be especially useful in disaster management and relief operations [Fajardo and Oppus, 2010]. Our focus is to enable developers to quickly deploy applications that take advantage of key sources that are fundamental for today’s networked citizens, including Twitter feeds, Facebook posts, current news releases, and government data. These ap- plications will also have the capability of empow- ering citizens involved in crisis situations to contribute via crowdsourcing, and to communicate up-to-date information to others. We will leverage several technologies to develop this application framework, namely (i) Linked Data principles for structured data, (ii) existing data sources and ontologies for disaster management, and (iii) App Inventor, which is a mobile application development framework for non-programmers. In this paper, we describe our motivating use cases, our architecture, and our prototype implementation.