Invalid Schemas and Conformance Use of WFS-T Use of Locking

48 Copyright © 2006 Open Geospatial Consortium – All rights reserved

11.3.4 Invalid Schemas and Conformance

As noted in the interoptability experiments, the XML Schema information provided by DescribeFeatureType is occasionally inaccurate. We can only assume that many of these Web Feature Servers are used for specific applications where the correct processing is known to that parties involved. In general we found conformance to WFS 1.0 specification to be very high.

11.3.5 Use of WFS-T

Several issues arise with respect to the use of WFS-T: The WFS 1.0 specification supports the idea PARTIAL_SUCCESS in response to a Transaction request. This model is not deterministic and interaction and its use is not advised. A WFS-T may perform additional integrity checks and produce a service exception based on application criteria rather then simply specification conformance. Correct use of the service may still produce a service exception. When performing a Transaction operation on more then one server both transactions should succeed or neither. This last point cannot be realized using the existing specification. A vendor extension should be feasible implementing a two-phased commit process. This would require an additional “Commit” operation to be called either by the CSW in the role of a Mediator, or by another WFS-T as part of fulfilling its Transaction request.

11.3.6 Use of Locking

A couple of practical difficulties arise out of the use of WFS Locking: Presentation to end-users, who expect to be able to work on a locked feature until their work is completed. The two operations allowing for Locks, GetLock and GetFeaturesWithLock, have little practical difference between them. We can only assume this was introduced as an optimization. Given the impedance between user expectations and the WFS locking model two options may be considered. Reveal the timed nature in which modifications may take place or delay obtaining a lock until the user has assembled a series of modifications to apply. The integrated client may remember which Features have been modified and limit the use of locking to an additional level of protection during the commit process. A lock, of limited duration, can be acquired for the modified Features – and then immediately used Copyright © 2006 Open Geospatial Consortium – All rights reserved 49 in a Transaction operation. This option forgoes the advantage of blocking other applications from making a modification while the end user is putting together a list of modifications.

11.3.7 Lack of Notification