The GeoViQua Quality-augmentation Broker provide a unified view over the existing GCI products, the GeoViQua quality indicators, and other user-generated information required to support the users in selecting the “best” data for their intended use.
Figure 1: GeoViQua broker main components
As shown in the picture, the GeoViQua Broker effectively complements and extends the GEO DAB, ensuring the consistency of the Producer and User quality models and implementing quality-constrained discovery.
The GeoViQua Broker is a Quality-enabled Discovery and Access Broker (DAB-Q) service, developed in the context of GeoViQua project. The DAB-Q is an extension of the GEO DAB (formerly known as EuroGEOSS Broker) and enables smart search and discovery functionalities using parameters relevant to GEO products (date, scale/detail, bounding box, SBA, etc.) extended to include quality information.
Quality information can be stated both by data producers and by data users, resulting in two conceptually distinct data models, the Producer Quality Model (PQM) and the User Quality Model (UQM) (also known as User Feedback model). These models together form the GeoViQua Quality Model, now in its final version 4.0 (http://schemas.geoviqua.org).
The DAB uses the CSW/ISO-Q that is an extension of the standard OGC Catalog Service for the Web 2.0.2 ISO Application Profile (CSW ISO AP) to support quality-constrained queries. Following the standard CSW behavior, the CSW/ISO-Q interface requires explicit quality statements in order to match query constraints. In other words, datasets without quality statements will never be returned as a result of a quality-constrained query.
The Capabilities document of the CSW/ISO-Q interface is available at the following endpoint:
Quality-constrained discovery is enabled by query constraints based on the above quality indicators. Such quality constraints are expressed against queryable properties (also referred to as “queryables”), which are selected concrete expressions of quality parameters/indicators both for the Producer Quality Model and User Feedback model.
The DAB-Q includes new several accessos. The WMS-Q accessor maps the WMS-Q Layers into ISO datasets according to specific requirements described in the WMS-Q version 2.0. The current WMS accessor of the DAB maps all the Layers of the Capabilities document. The bottom-level Layers are mapped into the ISO concept of dataset and all the Layers above in the hierarchy are mapped to the concept of dataset collection. The WAF accessor simply reads the XML files in the folder and tries to map them into the ISO 19115 standard. In the context of GeoViQua the WAF contains metadata based on the PQM, which will be mapped into a uniform data model implementing ISO 19115, based on official ISO 19139 schemas (http://essi-lab.eu/gvq/waf).
This component can be tested using the GI client (see Figure 1): http://geoviqua.essi-lab.eu/dabq-demo/gi-portal/index.jsp.
Figure 2: GI test portal