# How Knowledge Graphs Work

How a knowledge graph stores facts as nodes joined by named, one\-way edges, and how following those links answers questions like "Which prize did Marie Curie's daughter win?"

By Hari

Topic: Computing, AI & Electronics

[Open the interactive Jig](https://ask.jig.com/j/xjIxTA3d22Od)

## Transcript

### 1. A web of facts

A knowledge graph stores facts as a web\. Glowing dots are things, and the lines between them say how those things are connected\. Computers follow these lines to answer questions\.

Google’s Knowledge Graph launched in 2012 with over 500 million things and 3\.5 billion facts\.

### 2. Things become nodes

Each dot is called a node\. A node stands for one real thing: a person, a city, a chemical element or a prize\. Tap any node to see everything it is linked to\.

Wikidata, a free graph anyone can edit, holds over 100 million nodes, which it calls items\.

### 3. Links have names

Each line is called an edge, and every edge has a name, such as “born in” or “discovered”\. It also points one way\. Marie Curie discovered radium, but radium did not discover Marie Curie\!

### 4. A fact is a triple

Node, edge, node: these three pieces make one fact, called a triple\. It reads like a tiny sentence with a subject, a verb and an object\. Press the button to read the triples one by one\.

### 5. Kinds of things

A graph also keeps rules about what kinds of things exist, called a schema\. The colours show the kinds here\. A rule can say that a person can be born in a place, but a place cannot be born at all\.

### 6. Hop to an answer

Which prize did Marie Curie’s daughter win? No single edge says so\. Press the button and watch the graph hop from Marie Curie along “child”, then along “won”, to reach the answer\.

Irène Joliot\-Curie shared the 1935 Nobel Prize in Chemistry, 24 years after her mother won the same prize\.

### 7. Same word, different things

The word “curie” can mean a famous scientist or a unit for measuring radioactivity\. A knowledge graph gives each meaning its own node, so it can tell them apart\. Here the unit links back to the people it was named after\.

### 8. Graphs all around you

Search engines, voice assistants, museums and AI helpers use knowledge graphs to look up facts they can check\. A graph can still be wrong or missing things, so good graphs record where each fact came from\.

Wikidata has been edited more than 2\.5 billion times by people and helper programs\.