Example 5: Using the Reference Model to explain the technology details of common services (WP4 practices)
Descriptions of the Example
ENVRI working package 4 responses to deliver common services to support the constructions of ESFRI ENV RIs. Initially, the implementations focus on a data access subsystem that supports integrated data discovery and access. In order to help ESFRI project managers, architects, and developers understand the design and implementation of these services, this example uses the terms and concepts from the Reference Model to explain the technology details of these services.
How to Use the Reference Model
We start with the semantic harmonisation service developed by the team in Task 4.2 . The development is conducted to support the use case "Iceland Volcano Ash". The goal is to support scientists to analyse Iceland behaviour using data provided by different research infrastructures during a specific time period.
Defined by the Reference Model Science Viewpoint, the semantic harmonization is a behaviour belong to the data publication community, which captures the business requirements of unifying similar data (knowledge) models based on the consensus of collaborative domain experts to achieve better data (knowledge) reuse and semantic interoperability.
A data publication community interacts with a data access subsystem to conduct user roles. The computational specification of the data access subsystem is given in Figure 1. The model specifies a data access subsystem which provides data broker that act as intermediaries for access to data held within the data curation subsystem, as well as semantic brokers for performing semantic interpretation. These brokers are responsible for verifying the agents making access requests and for validating those requests prior to sending them on to the relevant data curation service. These brokers can be interacted with directly via virtual laboratories such as experiment laboratories (for general interaction with data and processing services) and semantic laboratories (by which the community can update semantic models associated with the research infrastructure).
The implementation conducted by WP4 T4.2 is an instantiation of the above computational objects specified in the Reference Model, that uses existing software components and developed approaches to enable integration and harmonization of data resources from cluster’s infrastructures and publication according unifying views.
Figure 2 depicts the computational components deployed in the prototype implementation. The service receives users’ requests via the SPARQL-endpoint. Then, it can automatically retrieve and integrate real measurement data collections from distributed data sources. The current prototype focuses on datasets from two different ESFRI projects:
- ICOS, which is organized by atmospheric stations which perform measurements of the CO2 concentration in the air and
- EURO-Argo observations that were provided in separate collections grouped according to the float that performed measurements of the ocean temperature.
The prototyped service uses two semantic models to provide mapping between representations: the RDF Data Cube vocabulary and the ENVRI vocabulary. The ENVRI vocabulary is derived from the OGC and ISO “Observations & Measurements” standard (O&M), SWEET and GeoSparql Vocabulary.
Table 1 provides the mapping between Reference Model computational objects and the deployed service components. Among them, the Transformation component serves as a data broker to negotiate data access with data stores within heterogeneous research infrastructures. An (instance of the) semantic broker is implemented using the RDF store technology which provides the semantic mappings and translations.
|RM Computational Objects||Deployed Service Components|
|Data Broker||Transformation (ICOS mappings, EuroArgo Mappings)|
|Semantic Broker||Provider’s data (ICOS data, EuroArgo data) |
Provider’s structures (ICOS structure, EurArgo structure)
|Semantic Laboratory||RDF Data Cube Vocabulary, |
In the following, we explain the design of the information model of the semantic harmonisation service.