Copyright © 2015 Open Geospatial Consortium.
37 Styles, Portrayal Rules, Symbol Sets with Symbols and Symbol definitions. The aim of
this ontology is to provide support for discovery of styles, symbols and symbol sets for supporting portrayal. The fact that this information is encoded semantically enables the
support of reasoning and extensions such as tradecraft information audience, purpose, functions, qualities information. Due to the lack of time, this ontology was not fully
formalized. This will need to be addressed in a future Testbed.
10 Portrayal Encoding
10.1 HSWG Portrayal Encoding
The HSWG Portrayal encoding was derived programmatically from the SKOS encoding of the taxonomy of HSWG Emergency Symbology which was captured manually the
testbed 10, as the symbols and incident types are matching one to one. The final results were split into three files:
The SKOS encoding of the HSWG Incident taxonomy; The Portrayal rules for HSWG which defines the HSWG Style and Portrayal
Rules; and The HSWG Symbol Set which defines the HSWG Symbol Set, associated
symbols, Symbol definitions, components and graphics. These three files were uploaded on the server in a RDF store and exposed through a
SPARQL endpoint and Portrayal catalog REST API.
10.2 EMS Portrayal Encoding
The Canadian EMS Portrayal encoding was derived programmatically from the SKOS encoding of the taxonomy of EMS which was captured manually for this testbed, as the
symbols and incident types are matching one to one. The final results were split into three files:
The SKOS encoding of the Canadian EMS Incident taxonomy; The Portrayal rules for EMS which defines the EMS Style and Portrayal Rules;
and The EMS Symbol Set which defines the EMS Symbol Set, associated symbols,
Symbol definitions, components and graphics. These three files were uploaded on the server in a RDF store and exposed through a
SPARQL endpoint and Portrayal catalog REST API.
38
Copyright © 2015 Open Geospatial Consortium.
11 Semantic Mediation
11.1 Introduction
Semantic Mediation was addressed to some extent in OWS-8, OWS-9 and OWS-10 see section 2 for references. These Testbeds were mostly focused on performing semantic
mediation for taxonomies. For example, gazetteers such as GNIS, GNS, Geonames often use different taxonomies for classifying feature types. To support semantic
mediation, mappings are required from one concept in a source taxonomy to another one in the target taxonomy using SKOS mapping relationships such as skos:exactMatch,
skos:broadMatch, skos:closeMatch. The semantic mediation has been demonstrated using Web Feature Service-Gazetteer WFS-G, however the mediation is performed as
black box on syntactic representation of the features using GML. Some extensions to the OGC Filter standard were added to accommodate the mediation of taxonomies. In
OWS-10, the hydrology sub-thread of CCI attempted to address a more general approach for mediation by defining some mapping between two different hydrologic models.
However, the solution was based on some UML tools that perform the mapping and no formal model was defined to encode the semantic mapping.
To address the semantic mediation of symbology in this testbed, we decided to address semantic mediation for linked data representation of information. We define semantic
mediation as the transformation from one conceptual model to another, in particular from one ontology to another. Instances of the target classes are created from the values of
instances of the source classes. We also wanted to formally addressthe semantic mediation for taxonomies by providing extensions to SPARQL to perform the semantic
mapping.
One of the goals of the semantic mediation approach is to provide an extensible, sharable encoding of the semantic mappings that can be processed by machine. For this purpose,
we leverage the existing linked data standards RDF, OWL, SPARQL to represent semantic mappings. These semantic mappings can be managed by a semantic mediation
service to perform transformation between two models. For this testbed, we demonstrated a RESTful Semantic Mediation Service that performed semantic mapping between the
HSWG Incident Model to the EMS Incident Model.
11.2 Review of existing approaches
This section provides an overview of the current existing approaches that attempt to address semantic mediation. A similar review was done in the OWS-8 ER. More up-to-
date information is provided here.