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Copyright © 2009 Open Geospatial Consortium, Inc.Copyright © 2009 Open Geospatial Consortium, Inc.
this attribute specifies the callback mechanism type. An urn shall be used which is indicated in the extended Capabilities metadata. To indicate the supported callback
mechanisms, the service metadata should be extended with the following structure:
Listing 11. WPS Capabilities Extension
A wps:CallbackOfferings element has 0..n wps:CallbackType each containing a urn.
For instance, the urn:ogc:wps:async:push:url will be used to indicate that the process results shall be send to the url stated in the callbackAddress attribute.
Both attribute have always to be used in conjunction. The status attribute has to be therefore always turned to false.
5.5.1.2 Use optional message parts
WS-Addressing OASIS, 2004 is a mainstream IT solution to this problem. The OASIS specification utilized the SOAP header to send a XML structure containing a callback
address. This callback address should be used to push the data back, when the process has finished.
A typical example can be seen in listing 12.
Copyright © 2009 Open Geospatial Consortium, Inc.Copyright © 2009 Open Geospatial Consortium, Inc.
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Listing 12. WS-Addressing Header Example
The WS-Addressing specification specifies its elements in detail. In the context of the WPS specification, if a WS-Addressing header is used, the expected response message to
a request will be delivered to a the given address stated in the wsa:Address element. Therefore, this mechanism can be used in conjunction with the request methods outlined
in the WPS specification.
In BPEL, the pattern described in listing 13 could be used to invoke a service with WS- Adressing.
Listing 13. WS-Addressing with BPEL
5.5.1.3 Comparison of both approaches
Both presented approach have certain advantages and disadvantages. Table 2 gives an overview:
Criteria WPS Inline Approach
WS-Addressing
Use within mainstream IT- architectures
- +
SOAP +
+ HTTP-POST
+ -
HTTP-GET +
-
