Nancy Wiegand

A Task-Based Ontology Approach to Automate Geospatial Data Retrieval

This paper presents a task-based and Semantic Web approach to find geospatial data. The purpose of the project is to improve data discovery and facilitate automatic retrieval of data sources. The work presented here helps create the beginnings of a Geospatial Semantic Web. The intent is to create a system that provides appropriate results to application users who search for data when facing tasks such as emergency response or planning activities. In our task-based system, we formalize the relationships between types of tasks, including emergency response, and types of data sources needed for those tasks. Domain knowledge, including criteria describing data sources, is recorded in an ontology language. With the ontology, reasoning can be done to infer various types of information including which data sources meet specific criteria for use in particular tasks. The vision presented here is that in an emergency, for example, a user accesses a Web-based application and selects the type of emergency and the geographic area. The application then returns the types and locations (URLs) of the specific geospatial data needed. We explore the abilities and limitations of the OWL Web Ontology Language along with other Semantic Web technologies for this purpose.

Handling semantic heterogeneities using declarative agreements

The focus of this paper is on interoperability issues to achieve data integration in distributed databases for geographic applications. Our concrete application is in the context of the State of Wisconsin Land Information System (WLIS). In WLIS, data is stored in XML using independently maintained local databases. However, answers to many queries must span several databases. Our approach is based on the existence of a central ontology and on declarative transformations, called \it agreements, between the schemas of the local databases and the central ontology. Using our approach, end users can seamlessly query and aggregate semantically related data that is available throughout the state using a visual interface. An expert at the site of the local database uses another visual interface to specify the agreement between that database and the ontology. Our approach has been fully developed and tested.

Investigating XQuery for querying across database object types

In addition to facilitating querying over the Web, XML query languages may provide high level constructs for useful facilities in traditional DBMSs that do not currently exist. In particular, current DBMS query languages do not allow querying across database object types to yield heterogeneous results. This paper motivates the usefulness of heterogeneous querying in traditional DBMSs and investigates XQuery, an emerging standard for XML query languages, to express such queries. The usefulness of querying and storing heterogeneous types is also applied to XML data within a Web information system.

A Web Query System for Heterogeneous Government Data

This paper describes a Web-based query system for semantically heterogeneous government-produced data. Geospatial Web-based information systems and portals currently are being developed by various levels of government along with the GIS community. Typically, these sites provide data discovery and download capabilities but do not include the ability to pose DBMS-type queries. One of the main problems in querying distributed government data sources is the difference in semantics used by various jurisdictions. We extend work in schema integration by focusing on resolving semantics at the value level in addition to the schema or attribute level. We illustrate our method using land use data, but the method can be used to query across other heterogeneous sets of values. Our work starts from an XML Web-based DBMS and adds functionality to accommodate heterogeneous data between jurisdictions. Our ontology and query rewrite systems use mappings to enable querying across distributed heterogeneous data.

A Web query system for heterogeneous geospatial data

This paper describes a Web-based query system for semantically heterogeneous geospatial data. Although Web-based information systems are currently being developed by the GIS community to provide data discovery and download capabilities for distributed Web data sets, they do not include the ability to pose DBMS type queries over the data. We developed a system that provides DBMS querying and that also resolves semantic differences that occur in distributed sources. We are working in the context of a proposed statewide land information system.

Review of Spatial databases with application to GIS by Philippe Rigaux, Michel Scholl, and Agnes Voisard. Morgan Kaufmann 2002.

Introduction This book presents methods for spatial data modeling, algorithms, access methods, and query processing. The main focus is on extending DBMS technology to accommodate spatial data. The book also includes spatial methods used in Geographic Information Systems (GISs). Historically, GISs developed separately from Database systems. GISs are specialized in all aspects of spatial data handling including spatial editing, re-projecting coordinate systems, and map display. However, their query abilities generally are limited or require low-level programming. Contrary to GIS software is the approach to include spatial data in DBMSs using ADTs and extensibility.

Querying Geospatial Data over the Web: a GeoSPARQL Interface

This paper describes our work to create an interface to facilitate querying using GeoSPARQL. GeoSPARQL is a recent extension to the RDF query language SPARQL in which spatial operators are added. Both SPARQL and GeoSPARQL are W3C standards. GeoSPARQL will be especially useful to geospatial specialists to be able to query RDF data containing spatial information over the Web, instead of loading data into a Geographic Information System (GIS). However, GeoSPARQL queries are difficult to write. To solve this problem, we developed a Web-based GeoQuery tool with an intuitive interface geared toward geospatial professionals. GeoQuery includes drop down lists to select attributes and to select spatial operators. Using user input, a query in GeoSPARQL syntax is automatically generated. Further, output is displayed on a map. GeoQuery uses the Parliament implementation of GeoSPARQL for query processing.

Preserving Detail in a Combined Land Use Ontology

Resolving land use codes between jurisdictions has been an on-going problem due to differences in terms and the nuances of partial similarity of concepts. This paper reports on creating a land use ontology that, contrary to being limited to the highest level of codes or to the most-often used codes, retains all codes. It is also novel in that it records the more subtle relationships between codes rather than just using subclassing. The purpose of creating this comprehensive type of ontology is to provide precise answers to searches of heterogeneous land use codes across jurisdictions. Land use affects important planning decisions, and detail is critical. To query the ontology, custom Java code was written, rather than using SPARQL, to be able to traverse down or up the tree to find the closest matching code when an exact match does not occur.

Ontology for the Engineering of Geospatial Systems

In this paper, a metamodel ontology is introduced to describe a domain of data components for geospatial data and query systems. The ontology satisfies the need to model the more complex environment that occurs within a geospatial system. For example, contrary to typical databases, geospatial data have additional metadata files describing the actual data. Also, a geospatial system may have domain ontologies in addition to semantic mappings. Currently, user knowledge is required to know the relationships between all data components (data, metadata, ontologies, mappings, etc.). Contrary to that, we propose a system ontology over which automatic inferencing can be done to determine relationships and meanings among data components. This work fits into the vision of the Semantic Web and interlinked data and knowledge networks and applies these notions to a metamodel for a data system.

SSO 2011 Workshop Report: 1st ACM SIGSPATIAL International Workshop on Spatial Semantics and Ontologies (SSO) 2011: (Chicago, IL - November 1, 2011)

We were pleased to organize the 1st Spatial Semantics and Ontologies (SSO) international workshop as part of the 19th ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems (ACM SIGSPATIAL GIS 2011). Semantic technologies are an emerging topic. This workshop was motivated by the need for semantics-related research for geospatial data and to provide a place for discussion and distribution of the work in this area. ACM SIGSPATIAL GIS 2011 offered a perfect venue to bring together computer scientists with spatial/geospatial domain experts, and this workshop was designed to help engage and create a synergy with computer and spatial scientists interested in the semantic area. We anticipated that technical advancements would be made by computer specialists focusing on the spatial area in collaboration with domain specialists who know the semantic problems they face. Having this workshop at ACM GIS opened the research to include wide areas of computer science.