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Applying WCO Ontology to Geospatial Web Coverage Services

Applying WCO Ontology to Geospatial Web Coverage Services. Xia Wang and Peter Baumann xia.wang@jacobs-university.de Jacobs University Bremen, Germany. Outline . Introduction Motivation Web Coverage Ontology (WCO) Applying WCO to Geospatial Web Coverage Services Conclusion. Introduction.

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Applying WCO Ontology to Geospatial Web Coverage Services

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  1. Applying WCO Ontology to Geospatial Web Coverage Services Xia Wang and Peter Baumann xia.wang@jacobs-university.de Jacobs University Bremen, Germany

  2. Outline • Introduction • Motivation • Web Coverage Ontology (WCO) • Applying WCO to Geospatial Web Coverage Services • Conclusion

  3. 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 data? @ ArcGIS • a raster consists of a matrix of cells (or pixels) organized into rows and columns (or a grid) • e.g.,a graphic, whereeach cell contains a value • representing information, e.g. temperature, humidity, elevation, • Ozone concentration, spectral info.

  4. Raster Service Application Fields • 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, ...

  5. coverage (services) • Raster = Coverage in OGC/GIS speak. • Coverage as a core abstract feature of raster data, denoting some "space-varying phenomenon" by ISO 19123. • Coverage services are becoming a very important kinds of web applications, especially in the geospatial domain. • Geography Markup Language (GML) 3.2.1 as a modeling language for geographic systems

  6. 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. 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. 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. 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 From GML 3.2.1 «Data Type» AbstractFeature (+x, -y) Order Domain Note:ISO 19123 generic-> many different implementations possible Predefined hook for metadata (1,2) (2,2) «Data Type» AbstractCoverage (1,1) (2,1) + coverageFunction: gml:CoverageFunction [0..1] + metaData [0..1] Range 3C° 5°C 7°C 11°C 1 1 1 domainSet rangeType rangeSet 1 1 1 «Union» «Data Type» «Data Type» DomainSet DataRecordPT RangeSet [OGC 09-146r1]

  10. Web Coverage Subtypes as per GML 3.2.1 «FeatureType» AbstractCoverage • 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. DiscreteCoverage ContinuousCoverage MultiSolidCoverage MultiPointCoverage RectifiedGridCoverage MultiSurfaceCoverage MultiCurveCoverage ReferenceableGridCoverage GridCoverage

  11. 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. WCO: concept Coverage

  13. WCO: concept GridCoverage

  14. WCO: GridCoverage Instance (a) (b) (c)

  15. 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. WCO: more complex web coverage • to define complex geometric web coverage • to define application related web coverage

  17. 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

  18. WCO: interoperation • Support WCS and WCPS standards • Support WCS services interoperation

  19. 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

  20. Thank you!

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