A persistent identifier (PID) acts as a standard, invariant and long-term reference of a digital resource, regardless of their status, their location or their current owner. Although, several EU Member States already have governance structures, processes, standards, guidelines and tools to create, maintain, manage and use persistent identifiers in their respective Spatial Data Infrastructures (SDI), their approaches are different and are at different levels of maturity. That is why the implementation of persistent identifiers for spatial objects is one of the most immediate challenges in the implementation of the INSPIRE Directive.
The first reference to the concept of PID in INSPIRE legislation is included in the article 8 (2) of the INSPIRE Directive. This article says that, in the case of spatial data sets corresponding to one or more of the themes listed in Annex I or II, the implementing rules shall include “a common framework for the unique identification of spatial objects, to which identifiers under national systems can be mapped in order to ensure interoperability between them”.
What is the purpose of this frame? To sum up:
- Identify or locate spatial objects by means of PID.
- Management of the cycle of life of spatial objects.
- Support reutilisation providing a PID for each resource.
- Define an interoperability framework among the different national systems of spatial objects identification.
Commission Regulation (EU) No 1089/2010, implementing Directive INSPIRE as regards interoperability of spatial data sets and services, defines in articles 9 and 10 how the model for PIDs must be. Experts responsible for technical aspects of INSPIRE recommend the use of HTTP URI to implement PID spatial objects.
Commission Regulation (EC) No 976/2009 implementing Directive INSPIRE as regards the Network Services determine location services must allow metadata searches by means of the spatial object PID.
In addition, view services must provide the PID of the resource used to create each layer. Finally, download services must also use these PIDs to show which datasets or specific spatial object is going to be downloaded.
However, in spite of the different references and recommendations about PIDs in INSPIRE, as it is stated in the study on RDF & PIDs for INSPIRE: State-of-Play for the project ARE3NA, it doesn´t exist a strategy for the governance of Persistent Identifiers (PIDs) shared for all the Member Estates and the European Commission. There is only a mention about the necessity of creating a common framework. Reports as Governance of Persistent Identifiers must be considered as a basis to create debate about the governance of PIDs in the frame of INSPIRE.
In Spain, the technical Standard on Interoperability of information resources reuse (NTI RRI) states in its part IV that reusable information resources will be identified by means of unique and unambiguous references using HTTP URI.
The need of defining a PID model adjusted to the legal framework outlined by INSPIRE and the NTI RRI, together with the broad variety of technical and organizational alternatives available, make PID a subject of great technical complexity and with important practical consequences in medium and long term.
Presently, GeoSLab is working together with the University of Zaragoza and the National Centre of Geographic Information (CNIG) in the definition and development of a system to assign and manage PIDs of spatial objects and datasets according to INSPIRE. A first prototype of this system was showed at the last edition of JIIDE 2016 and INSPIRE Conference 2016. The outcomes make us confident in the feasibility of the proposed solution and will serve as a basis to be evolved along this year.