WCPS :: OGC Huntsville, 2006-mar-08 Proposal for a Web Coverage Processing Service (WCPS) OGC, Huntsville, 2006-mar-08 Peter Baumann International University Bremen, rasdaman GmbH

2 WCPS :: OGC Huntsville, 2006-mar-08 Roadmap Motivation WCPS Concepts WCPS Functionality Wrapup

3 WCPS :: OGC Huntsville, 2006-mar-08 Roadmap Motivation WCPS Concepts WCPS Functionality Wrapup

4 WCPS :: OGC Huntsville, 2006-mar-08 Motivation WCS is foundation for coverage retrieval...but further server-side processing capabilities desirable WCS change requests! Ex: NDVI from multi/hyperspectral imagery adding more and more WCS functions not feasible Open-ended list of derivations – which to choose?...instead: coverage processing language Function nesting -> any complexity Server-side optimization possible

5 WCPS :: OGC Huntsville, 2006-mar-08 coverage retrieval and processing, based on WCS unlimited nesting -> expression language Declarative = describe what you want, not how to compute Not to substitute image processing! rigid formal definition for clear semantics Drawing upon imaging, DB, PL experience Application beyond geo(graphy): geophysics, engineering, … Any dimension; not restricted to spatio-temporal semantics powerful, but safe safe in evaluation = operations terminate in finite time No recursion WCPS Design Goals

6 WCPS :: OGC Huntsville, 2006-mar-08 Roadmap Motivation WCPS Concepts WCPS Functionality Wrapup

7 WCPS :: OGC Huntsville, 2006-mar-08 WPCS Coverage corresponds to WCS Coverage raster array + metadata Operations read coverages, combine coverages, return coverages...or ancillary coverage data includes WCS operations; nesting allows arbitrary complexity Request structure GetCapabilities-- WCS + processing capabilities ProcessCoverage-- request expression, referencing advertised coverages WCPS Concepts

8 WCPS :: OGC Huntsville, 2006-mar-08 Level 3: general meta data ( everything else; application dependent) Level 2: spatio-temporal metadata Domain: list of (AxisName,DomainExtent,AxisType) CRS Range: ordered list of (CompName,TypeName) Level 1: technical meta data Name (stored covg only) Cell domain: ordered list of (lo,hi); lo,hi int Null value Interpolation methods Level 0: coverage data Coverage values Coverage Constituents coverage data tech meta data geo descriptors Application data direct access, no encapsulation

9 WCPS :: OGC Huntsville, 2006-mar-08 Spatio-Temporal Semantics Level 1: "grid" coords axis identified by position number 0,1,... Addressing by (signed) int coordinates Level 2: spatio-temporal coords Axis name, unique per coverage Axis type, can be spatial/temporal At most one x, y, z, t Abstract axes possible CRS / geo coordinate refer to x/y spatial axes, time operations refer to t axis

10 WCPS :: OGC Huntsville, 2006-mar-08 Roadmap Motivation WCPS Concepts WCPS Functionality Wrapup

11 WCPS :: OGC Huntsville, 2006-mar-08 WCPS Requests GetCapabilities Like WCS, just some additional info ProcessCoverage Returns: 1..n coverages or scalar data Syntax close to XQuery: for c in ( coverageList ) [ where condition(c) ] return processingExpr(c) Example: for c in ( A, B, C ) return encode( c, "TIFF" ) ( tiff(A), tiff(B), tiff(C) )

12 WCPS :: OGC Huntsville, 2006-mar-08 Processing I Metadata extractionnull( C ); crs( C );... Encodingencode( C, "jpeg",.5 ) Induced operationsC1 + C2; C1 > 0; abs( C );... SubsettingC[ x0:x1, y0:y1 ]; C[ x0:x1, y0 ]; C[ x0, y0 ];... Level 1 x0,x1,y0 are integer cell coordinates Scalingscale( scale( C, 1, y0, y1, "nearest neighbor" ), 0, x0, x1, "nearest neighbor" ) again, Level 1 axis & coordinates are integers C: coverage valued expression

13 WCPS :: OGC Huntsville, 2006-mar-08 Processing II spatial transformstransform( C, p, EPSG:42424 ) returns Level 1 "grid" coordinate of p in C temporal transformttransform( C, Thu Nov 24 01:33:27 CET 2005 ) returns Level 1 "grid" coordinate of t in C reprojectionctransform( C, EPSG:42424, "barycentric" ) returns new coverage

14 WCPS :: OGC Huntsville, 2006-mar-08 Processing III Coverage constructorcoverage p in cdom( C ) values C[p] / 2 Condensercondense + over x in [1..99] using abs(C[x] – C[x-1]) Shorthands: add( C ), count( C ), max( C ), some( C ), all( C ),... Ex: 8-bit histogram coverage bucket in [0..255] valuescount( C = bucket ) For the theory behind & operator choice see, eg, VLDB Journal 1994, NGITS 1999

15 WCPS :: OGC Huntsville, 2006-mar-08 WCPS language expressions independent from encoding encode( C.red + C.nir, "Tiff" ) KVP encoding: WCPS language + entities where needed ? SERVICE=WCPS & VERSION=0.0.1 & REQUEST=ProcessCoverage & RESULT=encode(C.red%20+%20C.nir,%20%22Tiff%22) & STORE=true & EXCEPTIONS=application/vnd.ogc.se_xml XML encoding: XML Schema Language & Encoding

16 WCPS :: OGC Huntsville, 2006-mar-08 Motivation & idea WCPS Concepts WCPS Functionality Wrapup Roadmap

17 WCPS :: OGC Huntsville, 2006-mar-08 Status & Future Work Spec + XML Schemas published: OGC Reference implementation Break-through: done, full: under way [Georgi Chulkov] rasdaman + JSP Visual QL Web client [Ivan Delchev] Concepts proven in geo, life science, Grid in operational use since 5 years To do: Harmonization WCS 1.1; GML; ISO 19123; WPS; Filter Encoding Raster terminology Use cases Conformance clause

18 WCPS :: OGC Huntsville, 2006-mar-08 WCPS = WCS + coverage processing expression language Geography + geophysics + engineering +... Flexible, complex server-side data extraction (up to filter kernels) Clear semantics definition Suggestion to WG: Propose to TC as Discussion Paper Interest articulated by NASA, BEA, Cubewerx, Ionic Conclusion

19 WCPS :: OGC Huntsville, 2006-mar-08 Idea: WCPS as profile of WPS WPS execute services only informally described Formalized WCS extensions -> WCPS; further informal extensions -> WPS NB: formalization of WCS on the fly with WCPS wrap WCPS GetCoverage into WPS Execute ? WPS WG to be contacted WPS Relation WCS WCPS WPS generality degree of formalization WPS WCPS WCS

20 WCPS :: OGC Huntsville, 2006-mar-08 Discussion Arliss Whiteside: the levels effect also can be achieved via (i) profiles, (ii) processes using "transparent chaining" [abstract spec 12; doc ; Catalog Spec] Peter Vretanos: see Filter Encoding (filter spec related to WFS) Arliss Whiteside: non-Web Coverage Specification has related ideas (Coverage Service, ) Arliss Whiteside: how much interest is in forming an initial ad-hoc group? Will get thrust when 3 – 4 companies are interested. Interested in participating: Steven Keens, PCI; Ben Domenico, UCAR; Arliss Whiteside, BAE; Jerome Sonnet, Ionic; John Evans, GST; Peter Vretanos, Cubewerx

21 WCPS :: OGC Huntsville, 2006-mar-08 value changing operators format converters WCPS Operator Overview non-coverage functions general coverage manipulation set operators geometry operations