WPS implementation (nearly)

My WPS system now consists of a ASP.NET application wrapped around a ASP.NET Web Service. The web application takes the input and handles the getCapabilities and DescribeProcess requests. It also, after some error checking passes on the Execute request to the Web Service which processes the request asynchronously.

The WPS getCapabilities response can be seen here:

http://www.gmtu.gov.uk/wps/?service=WPS&version=1.0.0&Request=GetCapabilities

The DescribeProcess response can be seen here:

http://www.gmtu.gov.uk/wps/?service=WPS&version=1.0.0&Request=DescribeProcess&Identifier=DBSCAN

The DescribeProcess output is not yet complete as there is no description of the input and output data format. There is some error trapping so if you enter:

http://www.gmtu.gov.uk/wps/?service=WPS&version=1.0.0&Request=DescribeProcess&Identifier=noProcess

An error message will be returned.

The Execute process should return an XML response document that allows any client to monitor progress. In my implementation, for each request the WPS creates a file nnnnn.xml, where nnnnn is a unique integer. Both the wrapper application and the web service write to this file. When the Execute request has been parsed and all the inputs are present and correct, the wrapper creates the file with a ProcessAccepted message. When the Web Service is called, it overwrites the file with a ProcessStarted message. If there are any errors in processing then a ProcessFailed message is written. Finally a ProcessSucceeded message is written to the ResponseDocument. The idea is that the client can poll this document to check the process of the request.

This is sort of working but I have occasional errors “file being used by another process” when I try to overwrite the file or sometimes when reading it. I think this is due to the web server software (IIS) locking any file it has recently served. I’ll need to think of a way around this.