NGSI-LD

Information model The NGSI-LD information model can be considered as the first formal specification by a de jure standards organization of the property graph model, which has emerged since the early 2000s as an informal common denominator model for graph databases. The core concepts are: • A property graph (a.k.a. "attributed graph") is a directed multigraph, made up of nodes (vertices) connected by directed links, where nodes and arcs both may have multiple optional attached properties (i.e. attributes) • Properties (similar to attributes in object models) have the form of arbitrary key-value pairs. Keys are character strings and values are arbitrary data types. By contrast to RDF graphs, properties are not arcs of the graph. • Relationships are arcs (directed edges) of the graph, which always have an identifier, a start node and an end node The NGSI-LD meta-model allows users to provide, consume and subscribe to context information in multiple scenarios and involving multiple stakeholders. It enables close to real-time access to information coming from many different sources (not only IoT data sources), named Context Sources, as well as publishing that information through interoperable data publication platforms. It provides advanced geo-temporal queries, and it includes subscription mechanisms, in order for content consumers to be notified when content matching some constraints becomes available. The API is designed to be agnostic to the architecture (central, distributed, federated or combinations thereof), so that applications which produce and consume information do not have to be tailored to the specifics of the system that distributes/brokers context information for them. API operations comprise: • Context Information operations, concerned with Provision (creating NGSI-LD Entities, and updating their Attributes), Consumption (querying NGSI-LD Entities) and Subscription (subscribing to specific information, under specified constraints, in order to be notified when matching Entities appear, carrying the specified information). • Context Sources operations, concerned with Registration (make a new source of context information available in the overall distributed system, by registering it) and Discovery (querying the system about what context sources have registered, which offer information of a specified type). ==Uses==

NGSI-LD was initiated by partners of the FIWARE programme, and is primarily used by the FIWARE open source community, supported by the FIWARE Foundation as well as a diverse range of other projects and users such as below: • The Connecting Europe Facility recommends the use of the FIWARE context broker with NGSI-LD • The Open & Agile Smart Cities & Communities (OASC) organisation references the NGSI-LD specification as the first of their Minimal Interoperability Mechanisms (MIM1). • The Living-in.eu project recommends the use of NGSI-LD in their joint declaration and their technical commitments. The declaration has been endorsed and signed by 86 cities and public administrations from the EU, and is supported by many more companies and organizations. • The GSMA "IoT Big Data Framework Architecture" is based on NGSI-LD. • The Fed4IoT EU project, where it is used as a neutral data format for translating between various IoT data representations • The Thing'in graph-based digital twin platform from Orange uses NGSI-LD as its core information model. • The City Data Hub platform • The India Urban Data Exchange (IUDX) uses the NGSI-LD API as part of their Resource Access Service Interface. It is referenced in the Bureau of Indian Standards' Unified Data Exchange IS 18003(Part2):2021 standard. ==History==

NGSI-LD is the result of an evolution of Context Interfaces that started as part of the "Next Generation Service Interfaces" (NGSI) suite published by the Open Mobile Alliance (OMA) in 2012, which is also the source of the acronym NGSI. The NGSI suite included NGSI-9 as the Context Entity Discovery Interface and NGSI-10 as the Context Information Interface. The NGSI standard from OMA and its intermediary evolutions relied on a classical Entity–attribute–value model and an XML-based representation. The NGSI Context Interfaces were adapted by the FI-WARE project, which developed the platform for the European Future Internet Public-Private-Partnership (PPP). The OMA NGSI Context Interfaces got an HTTP binding with a JSON representation, referred to as NGSIv1, which included both NGSI-9 and NGSI-10. In the course of FI-PPP the interfaces further evolved into NGSIv2, which became the key interface of the FIWARE platform. After the end of the FI-PPP in 2016, the FIWARE platform became the core of the FIWARE Open Source Community managed by the FIWARE Foundation. In 2017, the ETSI Industry Specification Group on cross-cutting Context Information Management (ETSI ISG CIM) was created to evolve the Context Information Interface, which resulted in the creation of NGSI-LD. The limitations of the original information model led to the specification of a broader model which derives from property graphs, explicitly including relationships between entities, on a par with entities themselves. ETSI ISG CIM continues to evolve the NGSI-LD Information Model and API. It publishes new versions of the specification once or twice a year. ==See also==