3 Definition of terms, symbols and abbreviations

3.1 Terms

For the purposes of the present document, the following terms apply:

NOTE 1:
The letters "NGSI-LD" were added to most terms to confirm that they are distinct from other terms of similar/same name in use in other organizations, however, in the present document the letters "NGSI-LD" are generally omitted for brevity.
NOTE 2:
The use of URI in the context of the present document also includes the use of International Resource Identifiers (IRIs) as defined in IETF RFC 3987 [23], which extends the use of characters to Unicode characters [22] beyond the ASCII character set, enabling the support of languages other than English.

NGSI-LD Attribute: reference to both an NGSI-LD Property and to an NGSI-LD Relationship

NGSI-LD Attribute Instance (in case of temporal representation of NGSI-LD Entities): reference to an NGSI-LD Attribute, at a specific moment in time of its temporal evolution, usually identified by its instanceId

NGSI-LD Central Broker: NGSI-LD Context Broker that only uses a local storage when serving NGSI-LD requests, without involving any external Context Sources

NGSI-LD Context Broker: architectural component that implements all the NGSI-LD interfaces

NGSI-LD Context Consumer: agent that uses the query and subscription functionality of NGSI-LD to retrieve context information

NGSI-LD Context Producer: agent that uses the NGSI-LD context provision and/or registration functionality to provide or announce the availability of its context information to an NGSI-LD Context Broker

NGSI-LD Context Registry: software functional element where Context Sources register the information that they can provide

NOTE:
It is used by Distribution Brokers and Federation Brokers to find the appropriate Context Sources which can provide the information required for serving an NGSI-LD request.

NGSI-LD Context Source: source of context information which implements the NGSI-LD consumption and subscription (and possibly provision) interfaces defined by the present document

NOTE:
It is usually registered with an NGSI-LD Registry so that it can announce what kind of information it can provide, when requested, to Context Consumers and Brokers.

NGSI-LD Context Source Registration: description of the information that can be provided by a Context Source, which is used when registering the Context Source with the Context Registry

NGSI-LD Core API: core part of the NGSI-LD API that has to be implemented by all Brokers, including operations for providing or managing Entities and Attributes, operations for consuming Entities and checking which Entity Types and Attributes Entities are available in the system and operations for subscribing to Entities, receiving notifications and managing subscriptions

NGSI-LD Distribution Broker: NGSI-LD Context Broker that uses both local context information and registration information from an NGSI-LD Context Registry, to access matching context information from a set of distributed Context Sources

NGSI-LD Element: any JSON element that is defined by the NGSI-LD API

NGSI-LD Entity: informational representative of something that is supposed to exist in the real world, physically or conceptually

NOTE:
In the NGSI-LD API, any instance of such an entity is uniquely identified by a URI , and characterized by reference to one or more NGSI-LD Entity Type(s) .

NGSI-LD Entity Map: mapping of NGSI-LD Entity ids to Context Source Registrations used in maintaining atomicity of transactions performed by Distribution Brokers and Federation Brokers

NGSI-LD Entity Type: categorization of an NGSI-LD Entity as belonging to a class of similar entities, or sharing a set of characteristic properties

NOTE:
In the NGSI-LD API, an NGSI-LD Entity Type is uniquely identified by a URI .
EXAMPLE 1:
"Vehicle" is an NGSI-LD Entity Type and is identified with a proper URI.
EXAMPLE 2:
Bob's private car whose plate number is "ABCD1234" is an NGSI-LD Entity whose NGSI-LD Entity Type name is "Vehicle" .
EXAMPLE 3:
Alice's motorhome has a unique URI as id, but can be assigned multiple NGSI-LD Entity types, e.g. "Vehicle" and "Home" .

NGSI-LD External Linked Entity: Linked Entity that is identified through a dereferenceable URI which does not exist within the current NGSI-LD system

NOTE:
It can exist within another NGSI-LD system or within a non-NGSI-LD system.
EXAMPLE:
An NGSI-LD Entity, whose Entity Type name is "Book" , can be externally linked, through the "wasWrittenBy" relationship, to a resource identified by the URI "http://dbpedia.org/resource/Mark_Twain" .

NGSI-LD Federation Broker: Distribution Broker that federates information from multiple underlying NGSI-LD Context Brokers and across domains

NGSI-LD GeoProperty: subclass of NGSI-LD Property which is a description instance which associates a main characteristic, i.e. an NGSI-LD Value, to either an NGSI-LD Entity, an NGSI-LD Relationship or another NGSI-LD Property, that uses the special hasValue property to define its target value and holds a geographic location in GeoJSON format

NGSI-LD Internal Linked Entity: Linked Entity that exists within the current NGSI-LD system

EXAMPLE:
An NGSI-LD Entity, whose Entity Type name is "Vehicle", can be internally linked, through the "isParkedAt" relationship, to another NGSI-LD Entity, of Type name "Parking" , identified by the URI "urn:ngsi-ld:Parking:Downtown1" .

NGSI-LD JSONLDContext API: part of the NGSI-LD API that is used to host, serve and manage JSON-LD @contexts

NGSI-LD JsonProperty: subclass of NGSI-LD Property which is a description instance which associates a raw JSON literal value as a defined main characteristic to an NGSI-LD Entity, an NGSI-LD Relationship or another NGSI-LD Property and that uses the special hasJson (a subproperty of hasValue) property to define its target value

NOTE:
The target value contains data which is not available for interpretation.

NGSI-LD LanguageProperty: subclass of NGSI-LD Property which is a description instance which associates a set of strings in different natural languages as a defined main characteristic, i.e. an NGSI-LD Map, to an NGSI-LD Entity, an NGSI-LD Relationship or another NGSI-LD Property and that uses the special hasLanguageMap (a subproperty of hasValue) property to define its target value

NGSI-LD Linked Entity: NGSI-LD Entity referenced from another NGSI-LD Entity (the linking NGSI-LD Entity) via an NGSI-LD Relationship

NGSI-LD Linking Entity: NGSI-LD Entity which is the subject of a Relationship to another NGSI-LD Entity (the linked NGSI-LD Entity) or an external resource (identified by a URI)

NGSI-LD ListProperty: description instance which associates an ordered array of main characteristics, i.e. NGSI-LD Values, to either an NGSI-LD Entity, an NGSI-LD Relationship or another NGSI-LD Property and that uses the special hasValueList property to define its target value

NGSI-LD ListRelationship: description of an ordered array of directed links between a subject which is either an NGSI-LD Entity, an NGSI-LD Property or another NGSI-LD Relationship on one hand, and a series of objects, which are NGSI-LD Entities, on the other hand, and which uses the special hasObjectList property to define its target objects

EXAMPLE:
"A bus route services the following bus stops" can be represented by an NGSI-LD ListRelationship whose name is "route" which holds an array of directed links towards a series of NGSI-LD Entities of type (Type name) "BusStop" .

NGSI-LD Map: JSON-LD language map in the form of key-value pairs holding the string representation of a main characteristic in a series of natural languages

EXAMPLE:
"Bob's vehicle is currently parked on a street which is known as 'Grand Place' in French and 'Grote Markt' in Dutch" can be represented by an NGSI-LD LanguageProperty whose name is "street" which holds an NGSI-LD Map of two key-value pairs containing both the French ("fr" ) and Dutch ( "nl" ) exonyms of the street name.

NGSI-LD Null: "urn:ngsi-ld:null" or {"@none": "urn:ngsi-ld:null"} used as an encoding for null values

NGSI-LD Property: description instance which associates a main characteristic, i.e. an NGSI-LD Value, to either an NGSI-LD Entity, an NGSI-LD Relationship or another NGSI-LD Property and that uses the special hasValue property to define its target value

EXAMPLE:
"Bob's vehicle's speed is 40 km/h" can be represented by an NGSI-LD Property, whose name is "speed", and which characterizes an NGSI-LD Entity, whose NGSI-LD Type is "Vehicle" . Such a name can be expanded to a fully qualified name in the form of a URI , for instance "http://example.org/Vehicle" or "http://example.org/speed" .

NGSI-LD Query: collection of criteria used to select a sub-set of NGSI-LD Entities, matching the criteria

NGSI-LD Registry API: part of the NGSI-LD API that is implemented by the Context Registry, including operations for registering Context Sources and managing Context Source Registrations (CSRs), operations for retrieving and discovering CSRs, and operations for subscribing to CSRs and receiving notifications

NGSI-LD Relationship: description of a directed link between a subject which is either an NGSI-LD Entity, an NGSI-LD Property or another NGSI-LD Relationship on one hand, and an object, or unordered array of objects, each of which is an NGSI-LD Entity, on the other hand, and which uses the special hasObject property to define its target object

EXAMPLE 1:
An NGSI-LD Entity of type "Vehicle" can be the subject of an NGSI-LD Relationship whose object is an NGSI-LD Entity of type "Parking" .
EXAMPLE 2:
An NGSI-LD Entity of type "Vehicle" can be the subject of an NGSI-LD Relationship whose object is an array of NGSI-LD Entities of type "Passenger" .

NGSI-LD Scope: hierarchical structuring of Entities that enables restricting query results and notifications

NGSI-LD Temporal API: part of the NGSI-LD API pertaining to the Temporal Evolution of Entities, including operations for providing and managing the Temporal Evolution of Entities and Attributes, and operations for consuming the Temporal Evolution of Entities

NGSI-LD Temporal Evolution of an Entity: sequence of values attributed to an NGSI-LD Entity over time, i.e. its history or future predictions

NGSI-LD Tenant: user or group of users that utilize a single instance of a system implementing the NGSI-LD API (NGSI-LD Context Source or NGSI-LD Broker) in isolation from other users or groups of users of the same instance, so that any information related to one Tenant (e.g. Entities, Subscriptions, Context Source Registrations) are only visible to users of the same Tenant, but not to users of a different Tenant

NGSI-LD Value: JSON value (i.e. a string, a number, true or false, an object, an array), or JSON-LD typed value (i.e. a string as the lexical form of the value together with a type, defined by an XSD base type or more generally an IRI), or JSON-LD structured value (i.e. a set, a list, a language-tagged string)

EXAMPLE:
Bob's private car 'speed' NGSI-LD Value is the number 100 (kilometres per hour).

NGSI-LD VocabProperty: subclass of NGSI-LD Property which is a description instance which associates a string value which can be coerced to a URI as a defined main characteristic to an NGSI-LD Entity, an NGSI-LD Relationship or another NGSI-LD Property and that uses the special hasVocab (a subproperty of hasValue) property to define its target value

EXAMPLE:
"Bob's car is a non-commercial vehicle" can be represented by an NGSI-LD VocabProperty whose name is "category" which holds the string value "non-commercial" . If the associated JSON-LD context defines the term "non-commercial" as "http://example.com/non-commercial", then the returned value shall be expanded using JSON-LD type coercion into the URI the " http://example.com/non-commercial " .

3.2 Symbols

Void.

3.3 Abbreviations

For the purposes of the present document, the following abbreviations apply:

ABNF Augmented Backus-Naur Form
ALG1 Algorithm for transforming an NGSI-LD Entity into a JSON-LD document
AM Ante Meridiem
API Application Programming Interface
ASCII American Standard Code for Information Interchange
BNF Backus Naur Form
CH Switzerland
CSR Context Source Registration
ECMA European Computer Manufacturers Association
EU European Union
FI Future Internet
FQN Fully Qualified Name
GB Great Britain
GDPR General Data Protection Regulation
GeoJSON Geographic JavaScript Object Notation
GeoJSON-LD Geographic JavaScript Object Notation - Linked Data
GIS Geographic Information System
GPS Global Positioning System
HTTP Hypertext Transfer Protocol
HTTPS Hypertext Transfer Protocol Secure
IANA Internet Assigned Numbers Authority
ID Identifier
IEEE Institute of Electrical and Electronics Engineers
IETF Internet Engineering Task Force
IoT Internet of Things
IRI Internationalized Resource Identifier
ISG Industry Specification Group
ISO International Organization for Standardization
JSON JavaScript Object Notation
JSON-LD JSON Linked Data
LD Linked Data
LWM2M LightWeight Machine to Machine
M2M Machine to Machine
MIME Multi-purpose Internet Mail Extensions
MQTT Message Queuing Telemetry Transport
N/A Not Applicable
NGSI Next Generation Service Interfaces
NGSILD Next Generation Service Interfaces Linked Data (same as NGSI-LD)
NID Namespace Identifier
NSS Namespace Specific String
OAS Open API Specification
OMA Open Mobile Alliance
oneM2M oneM2M Partnership Project
PM Post Meridiem
POSIX Portable Operating System Interface
QoS Quality of Service
RDF Resource Description Format
REST Representational State Transfer
RFC Request For Comments
SAREF Smart Applications REFerence ontology
TCP Transport Control Protocol
TLS Transport Layer Security
TS Technical Specification
UCA Unicode Collation Algorithm
UL Ultra Light
UML Unified Modelling Language
URI Uniform Resource Identifier
URL Universal Resource Locator
URN Uniform Resource Name
UTC Coordinated Universal Time
UTF Unicode (or Universal Coded Character Set) Transformation Format