Page 54 - Redefining smart city platforms: Setting the stage for Minimal Interoperability Mechanisms - A U4SSC deliverable on city platforms

The implementation across (and even within) the city, or any application ecosystem, can be very
diverse and heterogeneous. An agreement on the interfaces is necessary in order to be able to
access the information. This is enabled by the context management API and the data models. The
common data and data models are available in a catalogue and guidelines are available so that
different verticals are integrated in a holistic/integrated city data lake to enable interoperability for
applications and systems among different cities and communities. The catalogue supports structural
interoperability, behavioural interoperability (representation, data mappings) and governance
interoperability.

8.1.3 Recommended specifications

– NGSI-LD, as specified by the ETSI Industry Specification Group on Context Information
Management (ETSI ISG CIM), provides an API for managing and requesting context information
and an underlying meta model based on entities – the core information elements, often the
digital counterparts of real-world objects – and their properties and relationships to other
entities. 41
– Even though the NGSI-LD specification has been published relatively recently, there are already
three Open-Source implementations (Scorpio, djane and Orion-LD). Orion-LD is the NGSI-LD
version of the Connecting Europe Facility (CEF) building block Context Broker.

– In addition, data models are needed that are, or can be made to be, compliant with NGSI-LD.
– NGSI-LD compliant data models for aspects of the smart city have been defined by organizations
and projects, including OASC, FIWARE, GSMA and the SynchroniCity project and there is an
ongoing joint activity of TM Forum and FIWARE to specify more.

– Existing data models and ontologies, e.g., the SAREF (Smart Applications REFerence ontology)
standard by ETSI/oneM2M, can be mapped for use with NGSI-LD by identifying the entities,
properties and relationships that can be managed and requested by the NGSI-LD API.

– oneM2M base ontology (that is compatible with SAREF). Additionally, oneM2M provides
the means to instantiate ontologies to provide semantic descriptions of the data exchanged
(through the use of metadata).

8.1.4 Verification

ETSI set up a Testing Task Force (TTF) to create a Testing toolkit to validate context brokers towards
the NGSI-LD specification. The result was a set of clearly defined test descriptions, test purposes
and executable robot scripts. All this information can be found on the ETSI CIM Website (ETSI, n.d.).

44 Redefining smart city platforms: Setting the stage for Minimal Interoperability Mechanisms