The first core service in the Linked Water Dataspace is the CATALOG that is the central registry of datasets. Within the CATALOG all water datasets, entities, and other sources of information are declared along with their descriptions. This includes a) the list of entities such as sensors or locations that are important for understanding water data and b) open data sources that are relevant to water management such as weather observation stations or forecast services. More specifically the CATALOG stores descriptive information about various sources of information.
The CATALOG service for Linked Water Dataspace, also referred to as the WKAN, is built on top of the CKAN dataset portal. In essence CKAN is an open source data portal developed for storing datasets and their descriptions. WKAN, the customized version of CKAN, has the added functionality to manage datasets and entities that are related to water management such as sensors, locations and users. Registering a dataset with the WKAN is the first step towards joining the dataspace. This enables applications and developers to access the dataset based on its description in the WKAN. In this regard, WKAN serves a critical role in the management of the dataspace; therefore, it requires regular updates from dataset owners to ensure correctness of data descriptions.
At the minimum level, the WKAN catalog provides predefined function calls in the form of RESTful API for queries related to dataset descriptions. Through this API the WKAN enables programmable access to its services; thereby, allowing applications to dynamically look for datasets and their access locations. The list of API call for WKAN includes:
- Get the list of datasets, entities, and other resources.
- Get the complete description of datasets and entities.
- Create, update, and delete datasets, entities, and other resources
- Get the list of all updates to datasets, entities, and other resources
- Search datasets and entities by keyword
For a detailed overview of the WKAN API the reader is recommended to consult the documentation of the RESTful API for CKAN open source software.
Further to expose our entity data in WKAN, we use OpenCube for exposing sensor aggregated readings.
OpenCube is the acronym of the project founded by the EU Seventh Framework Programme. The full name of the project is: Publishing and Enriching Linked Open Statistical Data for the Development of Data Analytics and Enhanced Visualization Services. The project aims at developing software tools that facilitate publishing of high-quality Linked Statistical Data and reusing distributed Linked Statistical Data in data analytics and visualizations. OpenCube is an ongoing project, and the final results are expected by the end of the year 2015.
The beta version of the OpenCube Toolkit (see Figure 21 for a sample page) is already available at the project website. The software is built upon the Open Source version of Information Workbench-Community Edition platform. The platform was used to ensure generic low-level functionalities such as shared data access, logging and monitoring. OpenCube Toolkit is still in development.
OpenCube Toolkit functionalities can be categorised as follows:
- Data Publishing: The platform allows data conversion to RDF from multiple formats: legacy tabular data (such as CSV/TSV files), relational databases, XML files and more. Moreover the data can be imported from external portals, such as CKAN instance (Open Source data management system). RDF data can be uploaded directly to the system or imported from selected a URL or a SPARQL endpoint.
- Data Reusing: The idea behind the project is to develop the tools that will allow easy data integration, analysis and visualisation. OpenCube Toolkit user interface is based on the templates system and widgets. A widget is an interface element which can be configured and embedded into a wiki page. For example it can display a list of the corresponding semantic resources.
A demo of using WKAN and OpenCube within the Waternomics platform is shown below.