1 SSO 1st Nov, 2011 Applying WCO Ontology to Geospatial Web Coverage Services Xia Wang and Peter Baumann Jacobs University Bremen, Germany

2 SSO 1st Nov, 2011 Outline Introduction Motivation Web Coverage Ontology (WCO) Applying WCO to Geospatial Web Coverage Services Conclusion

3 SSO 1st Nov, 2011 Introduction Textual data & raster (array) data on the (future) Web e.g., 1-D sensor time series, 2-D maps, 3-D x/y/t satellite image time series and x/y/z exploration data, 4-D x/y/z/t climate and ocean data, … massive multi-dimensional data, ranging into Terabytes, soon Petabytes different with the textual data at many levels What is raster ArcGIS a raster consists of a matrix of cells (or pixels) organized into rows and columns (or a grid) e.g.,a graphic, where each cell contains a value representing information, e.g. temperature, humidity, elevation, Ozone concentration, spectral info.

4 SSO 1st Nov, 2011 Sensor, image, statistics data Life Science: Pharma/chem, healthcare / bio research, bio statistics, genetics Geo: Geodesy, geology, hydrology, oceanography, meteorology, earth,space research,... Engineering & research: Simulation & experimental data in automotive/shipbuilding/ aerospace industry, turbines, process industry, astronomy, experimental physics, high energy physics,... Management/Controlling: Decision support, OLAP, data warehousing, census, statistics in industry and public administration,... Multimedia: e-learning, distance learning,... Raster Service Application Fields

5 SSO 1st Nov, 2011 coverage (services) Raster = Coverage in OGC/GIS speak. Coverage as a core abstract feature of raster data, denoting some "space- varying phenomenon" by ISO Coverage services are becoming a very important kinds of web applications, especially in the geospatial domain. Geography Markup Language ( GML ) as a modeling language for geographic systems

6 SSO 1st Nov, 2011 WCS 2.0 & WCPS 1.0 Web Coverage Services ( WCS ) as OGC standard allows to query and retrieve geospatial web coverages GetCapability, DescribeCoverage, and GetCoverage a WCS request can specify the retrieval by using a few simple operations, e.g., subsetting, cutout (trim), scaling, and reprojection. Web Coverage Processing Services (WCPS) defines a protocol- independent coverage processing language allowing clients to send requests of arbitrary complexity for evaluation by the server based on the conceptual model of WCS submitting QL-style requests for online data navigation and analysis in a set-oriented coverage expression language Constructor & condenser E.g., deriving the vegetation index, determining statistical evaluations, and generating different kinds of plots, like classification, histograms, etc

7 SSO 1st Nov, 2011 Motivation Large-scale raster data/apps are increasing sharply e.g, sensor, (satellite) image, statistics data in earth, space, life, and social sciences especially, flexible scalable web services on large(tera/peta-byte), multi-dimensional n- D array (pixel) data Current raster services targeted at humans “portryal”= surfing images, navigating maps Raster data & raster web services needs semantics Web Coverage Services (WCS): provides data + descriptions WPS, WPCS, WCS standards syntactically, functionally … Web service description, discovery, selection, composition, … Ex: Google map

8 SSO 1st Nov, 2011 Why Web Coverage Ontology (WCO)? WCO provides a formal approach to defined the semantic of web coverage and their features, constraints, relations and so on. WCO is designed for machines to digest. It further semantically supports WCS automatic discovery, composition, and interoperation. What we have done is, to build a core WCO based on the existing specifications and industry standards to keep the WCO as a small scale with good scalability. It can import and reuse other existing domain and application ontologies. to evaluate the WCO in geospatial domain, first

9 SSO 1st Nov, 2011 Web Coverage formal definition A coverage is a function from a spatial, temporal or spatiotemporal domain to an attribute range. A coverage associates a position within its domain to a record of values of defined data types (ISO 19123, 2005). A coverage consists of three primary elements:  a domain  a range  a mapping function «Data Type» DataRecordPT AbstractCoverage +coverageFunction: gml:CoverageFunction [0..1] +metaData [0..1] «Data Type» AbstractFeature «Union» DomainSet «Data Type» RangeSet 1 rangeSet 1 1 domainSet 1 1 rangeType 1 From GML Predefined hook for metadata Note: ISO generic -> many different implementations possible «Data Type» [OGC r1] (1,2)(2,2) (2,1)(1,1) Domain 3C° 5°C 7°C 11°C Range (+x, -y) Order

10 SSO 1st Nov, 2011 Web Coverage Subtypes «FeatureType» Abstract Coverage MultiSolid Coverage MultiSurface Coverage MultiCurve Coverage MultiPoint Coverage Discrete Coverage Continuous Coverage as per GML Rectified GridCoverage Referenceable GridCoverage Grid Coverage Coverage may be classified into different types, e.g., quadrilateral grid coverage, Thiessen polygon coverage, segmented curve coverage, and multipoint coverage (ISO19123, 2005) Most EO coverages are grid coverage.

11 SSO 1st Nov, 2011 WCO: web coverage types by geographic phenomena: discrete and continuous by the types of domain set: spatial, temporal, spatiotemporal, abstract axis axis={s,t,aaxis} e.g., if axis={s,t}, then it is a spatiotemporal; by dimension: 1D ~ 5D or more, |axis|= dim

12 SSO 1st Nov, 2011 WCO: concept Coverage

13 SSO 1st Nov, 2011 WCO: concept GridCoverage

14 SSO 1st Nov, 2011 WCO: GridCoverage Instance (b) (a) (c)

15 SSO 1st Nov, 2011 Apply the WCO to … model the complicated or real life web coverages, e.g., ThiessenPolygonCoverage, SegmentedCurveCoverage, … semantically classify/index of resources/coverages semantically query and retrieving of resources/coverages, and support the interoperation of different web coverage services and web coverage process services.

16 SSO 1st Nov, 2011 WCO: more complex web coverage  to define application related web coverage  to define complex geometric web coverage

17 SSO 1st Nov, 2011 WCO: query & reasoning WCO has been evaluated with a comprehensive test by running IRIS (wsml-rule) and PELLET (wsml-dl) reasoners. Queries are : At the level of Ontology: its satisfiability and validity At the level of Concepts: its concept, relations (ex: equivalent, sub-/sup), attributes At the level of datatypes: its values and value range (ex: > 2) At the level of intances: its specific values

18 SSO 1st Nov, 2011 WCO: query examples test1: ?Coverage[Domain hasValue ?Grid]memberOf Coverage and ?Grid[Dimension hasValue ?dimension]memberOf Grid and ?dimension>=2 test2: ?Point[pos hasValue ?pos,?srsName hasValue ?srsName]memberOf Point and ?pos[et1 hasValue ?et1,et2 hasValue ?et2]memberOf DoulbList

19 SSO 1st Nov, 2011 WCO: interoperation Support WCS and WCPS standards Support WCS services interoperation

20 SSO 1st Nov, 2011 Conclusion & Future work After formally defined a core WCO Ontology for geospatial web coverage services Primarily investigate how to apply the WCO into the related applications Future work will focus on the semantic of WCPS operations Also on extending the current semantic web technologies to support raster data and data types

21 SSO 1st Nov, 2011 Thank you!