NGSI-LD Step-by-Step

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This is a collection of NGSI-LD tutorials for the FIWARE system. Each tutorial consists of a series of exercises to demonstrate the correct use of individual FIWARE components and shows the flow of context data within a simple Smart Solution either by connecting to a series of dummy IoT devices or manipulating the context directly or programmatically.

How to Use

Each tutorial is a self contained learning exercise designed to teach the developer about a single aspect of FIWARE. A summary of the goal of the tutorial can be found in the description at the head of each page. Every tutorial is associated with a GitHub repository holding the configuration files needed to run the examples. Most of the tutorials build upon concepts or enablers described in previous exercises the to create a complex smart solution which is "powered by FIWARE".

The tutorials are split according to the chapters defined within the FIWARE catalog and are numbered in order of difficulty within each chapter hence the an introduction to a given enabler will occur before the full capabilities of that element are explored in more depth.

It is recommended to start with reading the full Core Context Management: The NGSI-LD Interface Chapter before moving on to other subjects, as this will give you an fuller understanding of the role of context data in general. However it is not necessary to follow all the subsequent tutorials sequentially - as FIWARE is a modular system, you can choose which enablers are of interest to you.

Prerequisites

Swagger

The OpenAPI Specification (commonly known as Swagger) is an API description format for REST APIs. A Swaggger spec allows you to describe an entire API (such as NGSI-LD itself) however in this tutorial we shall be concentrating on using Swagger to define data models.

API specifications can be written in YAML or JSON. The format is easy to learn and readable to both humans and machines. The complete OpenAPI Specification can be found on GitHub: OpenAPI 3.0 Specification. This is important since we will need a well defined structure to be able to generate @context files.

Docker and Docker Compose

To keep things simple all components will be run using Docker. Docker is a container technology which allows to different components isolated into their respective environments.

  • To install Docker on Windows follow the instructions here
  • To install Docker on Mac follow the instructions here
  • To install Docker on Linux follow the instructions here

Docker Compose is a tool for defining and running multi-container Docker applications. A series of *.yaml files are used configure the required services for the application. This means all container services can be brought up in a single command. Docker Compose is installed by default as part of Docker for Windows and Docker for Mac, however Linux users will need to follow the instructions found here

You can check your current Docker and Docker Compose versions using the following commands:

docker-compose -v
docker version

Please ensure that you are using Docker version 18.03 or higher and Docker Compose 1.21 or higher and upgrade if necessary.

If using a linux distro with an outdated docker-compose, the files can be installed directly as shown:

sudo curl -L "https://github.com/docker/compose/releases/download/1.24.0/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose

If you are using docker-compose in Ubuntu with VMware and faced the following error: ERROR: Couldn't connect to Docker daemon at http+docker://localunixsocket - is it running?

It can be solved by owning the /var/run/docker.sock Unix socket as shown:

sudo chown $USER /var/run/docker.sock

Postman

The tutorials which use HTTP requests supply a collection for use with the Postman utility. Postman is a testing framework for REST APIs. The tool can be downloaded from www.getpostman.com. All the FIWARE Postman collections can downloaded directly from the Postman API network

Cygwin for Windows

We will start up our services using a simple Bash script. Windows users should download cygwin to provide a command-line functionality similar to a Linux distribution on Windows.

Apache Maven

Apache Maven is a software project management and comprehension tool. Based on the concept of a project object model (POM), Maven can manage a project's build, reporting and documentation from a central piece of information. Maven can be used to define and download our dependencies and to build and package Java or Scala code into a JAR file.

Data models

The tutorials defines a series of data-models to be used within the @context. More information about the classes and attributes used can be found in the following:

List of Tutorials

Core Context Managment: The NGSI-LD Interface

These first tutorials are an introduction to the NGSI-LD Context Brokers, and are an essential first step when learning to use NGSI-LD

  101. Understanding @context
  102. Working with @context
  103. CRUD Operations

Internet of Things, Robots and third-party systems

In order to make a context-based system aware of the state of the real world, it will need to access information from Robots, IoT Sensors or other suppliers of context data such as social media. It is also possible to generate commands from the context broker to alter the state of real-world objects themselves.

  201. Introduction to IoT Sensors
  202. Provisioning the Ultralight IoT Agent
  203. Provisioning the JSON IoT Agent

Core Context Management: History Management

These tutorials show how to manipulate and store context data so it can be used for further processesing

  304. Querying Time Series Data (Crate-DB)
  305. Big Data Analysis (Flink)
  306. Big Data Analysis (Spark)

Processing, Analysis and Visualization

These tutorials show how to create, process, analyze or visualize context information

  507. Cloud-Edge Computing