From Geostandards

The goal

The Directive defines "interoperability" as (see Article 3(7)):

‘interoperability’ means the possibility for spatial data sets to be combined, and for services to interact, without repetitive manual intervention, in such a way that the result is coherent and the added value of the data sets and services is enhanced.

The starting point

Typical characteristics of the access to spatial data traditionally are:

• Spatial data is exchanged in complete data sets either via digital media or downloads
• The user has to deal with interpreting heterogeneous data in different formats and (s)he has to identify, extract and post-process the subset of the data (s)he needs.
• Often the data is insufficiently described.

The result is a lack of interoperability.

What INSPIRE is aiming at

INSPIRE aims at addressing the interoperability issues with the following measures:

• Provide access to spatial data online, i.e. via the internet and via well-defined network services.
• Make data available according to commonly agreed data specifications.

As a result, the source data sets in Member States may stay as they are (with the exception of the harmonisation of geography of spatial objects spanning borders as required by Article 10(2). For the provision of the existing spatial data sets, data or service providers have to provide a transformation between their internal data model and the harmonised INSPIRE data specification.

Three general alternatives exist to execute the necessary transformation:

1. “On-the-fly“ transformation of the spatial data on request in the view and download service
2. Offline transformation of spatial data and provision of the transformed data
3. Provision of the source data as-is via the view and download service and transformation of the spatial data by a separate transformation service

The INSPIRE Directive states in articles 7(3) and 11(1) that "spatial data sets shall be made available in conformity with the implementing rules either through the adaptation of existing spatial data sets or through […] transformation services" that enable "spatial data sets to be transformed with a view to achieving interoperability." The Directive leaves a choice where and how the transformation occurs.

The choice of the most appropriate implementation strategy will depend on several factors including:

• the complexity of the necessary transformation
• the availability of adequate software tools and know-how
• the roles and responsibilities in a Member State for the provision of the data
• the cost for each alternative
• the processes that should occur in the transformation (e.g. validation and conformity checks, fusion with other data sets, etc)

An issue for INSPIRE is that while the need for transformations of data (and queries to a network service) is widely recognised and implementations exist, currently no common language or at least a metric for such transformations exists. Neither OGC nor ISO/TC 211 have addressed this topic as part of their work so far.

In addition, existing data sets are usually documented in very different ways.

Therefore, the current assumption is that transformations are treated mostly as a „black-box“ (transformation details are only known to the provider) and not detailed in INSPIRE specifications. The decision, if transformations are done offline, on-the-fly behind the download/view service interface or in a separate transformation service is left to the provider.

Still, to understand the mapping of existing data to an INSPIRE schema better and more objectively, it would be very beneficial to have a metric of the complexity of a transformation. Without such a metric it is not easy to objectively assess the feasibility of an INSPIRE application schema in terms of transformability with respect to the existing data sets.

Data providers may also choose to align their internal data model with the harmonised data specifications and extend these based on their requirements. See also Extensions by countries or communities.

Currently the transformation from existing source data sets to the harmonised INSPIRE data specifications will often be quite complex. However, it is the hope and expectation that future data specifications developed in Europe use the INSPIRE data specifications as a basis, when practicable. This would simplify the transformation of source data to the INSPIRE data view significantly.

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