Nowadays, National, regional or local governments are promoting different initiatives to publish their information using Open Data portals. In the scope of geographic information these efforts for publication of information is based on Spatial Data Infrastructures (SDIs) and European Directive INSPIRE (2007/2/CE). The link between both spheres, Open Data and SDIs is more than desirable, and, in fact, it is possible thanks to solutions similar to which we will explain in next paragraphs.
One of the main achievements of Law 14/2010, of 5 July, about Infrastructures and Services of Geographic Information in Spain (LISIGE), that transposes European Directive INSPIRE, is that Public Administrations have opened to users a big quantity of geographic information restricted so far for internal use.
To make it possible, they have progressively implemented different kinds of web services to facilitate access to their resources (visualization services, download services, etc.) Especially relevant has been the importance of the role played by metadata. This law obliges Public Administrations to create metadata of quality to describe their geographic resources and to make them accessible by means of location services.
Therefore, it would be advisable to take advantage of these efforts made by different Governments to publish their geographic information, defining strategies to offer it using their Open Data portals. That would avoid the duplication of information and extra charges for maintenance. The Community of users of CKAN has developed two extensions focused in these objectives.
CKAN is an Open Source platform that can be used by any entity to build and customize an Open Data Portal. It incorporates tools for data publishing and maintenance, different search possibilities, management of users, roles and permissions and a API (Application Programming Interface) to be integrated in other applications and services to facilitate data access and exploitation. In its Website you can find a complete description of functionalities and some examples of use (European Data Portal or United Kingdom Data Portal, among others).
One of the most relevant features of CKAN is the possibility of adding extensions, what widens the potential of this tool. The extension we are interested in this case is ckanext-harvest. It allows the integration of external data sources in CKAN. Periodically, the platform will connect to these external sources to harvest the description of their resources and will stored them inside CKAN. this way, the base information is in the original source and the Open Data Portal keeps only an automatic copy, avoiding duplicities and costs of maintenance.
The extension ckanext-harvest includes also a web client that facilitates data harvesting, allowing the definition of basic characteristics of each work, such as title, description, URL, type of source, updating frequency, the entity to which this source is associated and a section where other parameters can be added (list of additional fields for metadata of the source). Furthermore, it offers functionalities to monitor and manage the execution of each work: execute again the harvest, resume of the last execution, list of compiled resources, clear/delete data of previous executions, etc.
To foster this extension in the frame of SDIs, it is necessary to install another extension: ckanext-spatial. This extension makes possible the addition of a metadata catalogue with standard interface CSW, as harvest data source. The extension can analyse the metadata codified following the schema of ISO 19139 and extract the adequate proprieties for integration in CKAN Open Data Portal.
To sum up, if an entity wants to launch its own Open Data Portal and make the most of all the geographic information already catalogued, the use of CKAN, together with its extensions ckanext-harvest and ckanext-spatial seems to be a good option to save in costs of implementation and future maintenance.