The action defined alternative encoding rules (mainly for the purpose of viewing/analysis in mainstream GIS systems) for a number of selected application schemas and a template and procedure for proposing and endorsing additional encoding rules in the future.
Specifically, it carried out the following tasks:
The full action mandate is attached: MIWP-2017.2_Alternative_encodings_Action_mandate_endorsed.pdf
The outputs of the Action are made available on GitHub.
The results include the following:
Regular virtual meetings took place on Fridays from 10:00-11:30 CE(S)T
The current data specification TGs define (complex) xml schemas based on GML as the default encoding for all INSPIRE spatial data themes. Many existing (web and desktop) applications and tools have difficulties in consuming and/or fully making use of data shared according to these schemas.
The INSPIRE xml schemas are complex, because they are generated automatically from the conceptual UML model (according to the normative UML-to-GML encoding rules described in the GML standard and INSPIRE Technical Guidelines D2.7 Encoding Guidelines) and therefore reflect all the complex structures present in the conceptual model. In contrast, most existing clients, including the popular GDAL/OGR open source library (that is underlying most OS and proprietary client solutions) consumes and writes flat data structures, where e.g. each attribute can only have at most one value and attributes can have only simple types (e.g. integer, string, boolean) and not complex ones. This means that, while INSPIRE data encoded according to the current schemas can be downloaded and viewed, simple use (visualisation, simple joins, visual overlays, spatial search, …) is difficult in standard GIS clients.
One way to address this gap is to create alternative encodings for basic data exchange and direct visualisation in standard GI tool (another one is to encourage better support for consuming INSPIRE data by vendors – this solution was investigated in Action 2017.3).
Proposals already exist for alternative encodings, mainly for simplified XML schemas (this approach is often also referred to as "flattening" of the existing xml schemas and has been applied e.g. in the ELF project or the example presented by DK in the 2nd 2016.1 meeting and is already implemented in tools, e.g. ShapeChange), but also for RDF vocabularies or ESRI geodatabase structures. Alternative encodings could also be based on other standards such as JSON or GeoPackage.
According to Art. 7 of the IRs on data interoperability, alternative encodings can be used as long as an encoding rule is publicly available that specifies schema conversion rules for all spatial object types and all attributes and association roles and the output data structure used. Such an encoding rule would need to include cross-cutting aspects (e.g. how to flatten recurring complex structures such as geographical names) as well as theme-specific aspects.
The work was carried out by a temporary MIG sub-group, coordinated by JRC and supported by a contractor. The call for participation is available here.
The temporary sub-group carried out its work in several meetings during 2018 and 2019 and via electronic exchange. Meeting minutes are kept in this wiki space. Discussions, examples and the Good Practice documents are held on Github.