Problem Statement and Description

106 Copyright © 2013 Open Geospatial Consortium.

10.5 Aspects Not Covered by Main Scenario

The aspects described in the following subsections were removed from the main scenario because the actions they define are considered to have already been performed. In other words, the results of these actions are preconditions for the main scenario. 11 Lessons Learned

11.1 Inconsistent Data Publication Models

11.1.1 Problem Statement and Description

As OGC standards, such as AIXM 5.1, are being increasing deployed in operational production environments by data publishers, differing interpretations of the standards become an obstacle to interoperability. It appears that the data publishers are interpreting the standards to create their own publication mechanisms and the complexity of the standards and the nuances in this interpretation lead to incompatibility among the data publishers. A few examples illustrate the point: 1. A data publisher exchanges its data as AIXM 5.1 to a wide range of stakeholders and assigns each feature a UUID. The consumers of that data assign a new UUID to satisfy their internal data manipulation needs. The results are multiple sets of UUIDs for describing the same features. As data publishers continue to expand their own data exchanges with other stakeholders, the probability that a consumer may end up with multiple instances of the same feature data in its database. In the near term, UUID look-up tables can resolve the issue but other long-term mechanisms need to be put into place. 2. A related but different example may be found in a comparison of data sets from various data publishers. In this instance, different interpretations of the XLink href’s can render the data sets incompatible. The error is due to one publisher encoding the value of the XLink href not with the value assigned in the gml:id but the gml:identifier UUID plus a prefix urn:uuid. In order to use the data, another publisher would have to strip out the urn:uuid: prefix and then use the UUID value to generate a join back to the relevant feature so it could be published with a valid XLink href value. To further illuminate the problem, the Xlinks used in the data follow the specification of Abstract references in http:www.aixm.aerogallerycontentpublicAIXM51AIXM_Feature_I dentification_and_Reference-1.0.pdf. Section 3.4.1 which points to the gml:identifier, not the gml:id though there is a recommendation on how the gml:id should be chosen given the gml:identifier of the feature. The result of interpreting the nuances of the standard is incompatible data sets. Copyright © 2013 Open Geospatial Consortium. 107

11.1.2 Recommendations