WPS Architecture Section

In this section you can find description of the 52°North WPS Architecture.

The 52°North WPS supports a set of input formats, processes and output formats. The architecture is held pluggable to enable the extension of already supported formats and processes. In detail, the parsers (green arrows) transform external data formats (such as GML, SHP, etc.) into internal dataformats. The internal dataformat is consumed by the process itself. The process also outputs a specific internal data format. That internal dataformat is transformed back to the requested external output format via so called "Generators".

The following diagrams provide a detailed overview of the architecture.

Server module

All processes have to implement IAlgorithm or is one of its implementing abstract classes. The AbstractSelfDescribingAlgorithm class offers convenient methods to automatically create a ProcessDescription document. For a tutorial follow this link.

All processes are organized in so called "Algorithm Repositories", which have to implement IAlgorithmRepository. Each Algorithm Repository decides independently on how to load a process. All backends such as GRASS and ArcGIS Server implement their own Algorithm Repository. The LocalAlgorithmRepository is for locally available Java classes that implement IAlgorithm and the UploadedAlgorithmRepository for processes uploaded via the web interface (see the bottom of this tutorial).

IO module

The internal datastructures (such as Geotools FeatureCollection and so on) are wrapped by the datastructures seen above. They all have to implement the IData interface. It is distinguished between literal and complex data according to the WPS specification. The following table gives you an overview of the available complex datatypes.

Class	Description
AsciiGrassDataBinding	A datastructure that provides Asciidata consumed by GRASS
FileDataBinding	A datastructure that holds a reference to any kind of file
GeotiffDataBinding	A datastructure that holds a reference to a Geotiff file
GTRasterDataBinding	A Geotools datastructure that represents a raster (GridCoverage2D)
GTVectorDataBinding	A Geotools datastructure that represents a vector data (FeatureCollection)
PlainStringDataBinding	A datastructure that holds a String
ShapefileDataBinding	A datastructure that holds a reference to a Shapefile
GenericFileDataBinding	A datastructure that holds a reference to FileDataBinding, which references a file and adds some convenience methods object

Parsers package

Parser have to implement the IParser interface. It is distinguished between XML and binary parsers as toplevel abstract classes. Parser may also implement the IStreamableParser interface if they support streaming. There are currently the following parsers:

Class	ExternalDatatype consumed	InternalDatatype created
GTBinZippedBase64SHPParser	Base64 encoded zipped Shapefiles	GTVectorDataBinding
GTBinZippedSHPParser	Zipped Shapefiles (per reference)	GTVectorDataBinding
GML3BasicParser	GML3	GTVectorDataBinding
GML3BasicParser4Files	GML3	GenericFileDataBinding referencing a GML3 file
KMLParser	KML	GTVectorDataBinding
SimpleGMLParser	GML2 following the basic.xsd	GTVectorDataBinding
GRASSKMLParser	KML	GenericFileDataBinding referencing a KML file
GML2BasicParser4Files	GML2	GenericFileDataBinding referencing a GML2 file
GML2BasicParser	GML2	GTVectorDataBinding
GTBinZippedWKT64Parser	Base64 encoded zipped WKT	GTVectorDataBinding
GeotiffBase64Parser	Base64 encoded Geotiff	GTRasterDataBinding
GeotiffParser	Geotiff (per reference)	GTRasterDataBinding
GeotiffZippedParser	Zipped Geotiff (per reference)	GTRasterDataBinding
AsciiGrassParser	GrassAsciiGrid	AsciiGrassDataBinding
GenericFileParser	Any file	GenericFileDataBinding

All parser have to be registered either directly in the wps_config.xml file in the config folder or via the webAdmin configuration GUI.

Generators package

Generators have to implement the IGenerator interface. It is distinguished between XML and binary generators as toplevel abstract classes. Generators may also implement the IStreamableGenerator interface if they support streaming. There are currently the following generators:

Class	InternalDatatype consumed	ExternalDatatype created
GenericFileGenerator	GenericFileDataBinding	Content of the file (base64 encoded-depending on request)
GeotiffGenerator	GTRasterDataBinding	Geotiff
KMLGenerator	GTVectorDataBinding	KML
GML2BasicGenerator	GTVectorDataBinding	GML2
GML2BasicGenerator4Files	GenericFileDataBinding	GML2
GML3BasicGenerator	GTVectorDataBinding	GML3
GML3BasicGenerator4Files	GenericFileDataBinding	GML3
Base64Generator	FileDataBinding	base64 encoded file
GTBinZippedSHPFileGeneratorBase64	GTVectorDataBinding	Base64 encoded zipped Shapefile
GTBinZippedSHPGenerator	GTVectorDataBinding	Zipped Shapefile (only for reference/store)
SimpleGMLGenerator	GTVectorDataBinding	GML2 following basic.xsd
GRASSXMLGenerator	GenericFileDataBinding	KML/XML

There are also three specialized Generators for storing the result directly in a WMS/WFS/WCS and retrieving a reference to the service with the corresponding stored georesource (layer/FeatureType).

GeoserverWMSGenerator	GTVectorDataBinding/GTRasterDataBinding	WMS
GeoserverWFSGenerator	GTVectorDataBinding	WFS
GeoserverWCSGenerator	GTRasterDataBinding	WCS

In these cases the mimetype has to be set to application/WMS or application/WFS or application/WCS

A sample response looks like this

<ns:ComplexData encoding="UTF-8" mimeType="application/WMS">
        <OWSResponse type="WMS">
                <ResourceID>N52:tempFile1284329891171</ResourceID>
                <GetCapabilitiesLink>
                        http://localhost:8080/geoserver/ows?Service=WMS&amp;Request=GetCapabilities&amp;Version=1.1.0
                </GetCapabilitiesLink>
        </OWSResponse>
 </ns:ComplexData>

All generators have to be registered either directly in the wps_config.xml file in the config folder or via the webAdmin configuration GUI.

GetCapabilities sequence diagram

DescribeProcess sequence diagram

Execute sequence diagram