This article is a part of a series intended to show how to use Memgraph on real-world data to retrieve some interesting and useful information.

We highly recommend checking out the other articles from this series which are listed in our tutorial overview section.

Introduction

​TED is a nonprofit organization devoted to spreading ideas, usually in the form of short, powerful talks. Today, TED talks are influential videos from expert speakers on almost all topics — from science to business to global issues. Here we present a small dataset which consists of 97 talks, show how to model this data as a graph and demonstrate a few example queries.

Data Model

• Each TED talk has a main speaker, so we

  identify two types of nodes — Talk and Speaker.

• We add an edge of type Gave pointing to a Talk from its main Speaker.

• Each speaker has a name so we can add property name to Speaker node.

• We'll add properties name, title and description to node

  Talk.

• Each talk is given in a specific TED event, so we can

  create node Event with property name and relationship InEvent between

  talk and event.

• Talks are tagged with keywords to facilitate searching, hence we

  add node Tag with property name and relationship HasTag between talk and

  tag.

• Users give ratings to each talk by selecting up to three

  predefined string values. Therefore we add node Rating with these values as

  property name and relationshipHasRating with property user_count between

  talk and rating nodes.

Importing the Snapshot

We have prepared a database snapshot for this example, so the user can easily import it when starting Memgraph using the --data-directory option.

sudo -u memgraph \
  /usr/lib/memgraph/memgraph --data-directory /usr/share/memgraph/examples/TEDTalk \
    --storage-snapshot-interval-sec=0 --storage-wal-enabled=false \
    --storage-snapshot-on-exit=false --storage-properties-on-edges=true

When using Memgraph installed from a Debian or RPM package, the currently running Memgraph server needs to be stopped before importing the example, using the following command:

systemctl stop memgraph

When using Docker, the example can simply be imported with the following command:

docker run -p 7687:7687 \
  -v mg_lib:/var/lib/memgraph -v mg_log:/var/log/memgraph -v mg_etc:/etc/memgraph \
  memgraph --data-directory /usr/share/memgraph/examples/TEDTalk \
  --storage-snapshot-interval-sec=0 --storage-wal-enabled=false \
  --storage-snapshot-on-exit=false --storage-properties-on-edges=true

The user should note that any modifications of the database state will persist only during this run of Memgraph.

Example Queries using OpenCypher

In the queries below, we are using Cypher to query Memgraph via the console.

1) Find all talks given by specific speaker:

MATCH (n:Speaker {name: "Hans Rosling"})-[:Gave]->(m:Talk)
RETURN m.title;

2) Find the top 20 speakers with most talks given:

MATCH (n:Speaker)-[:Gave]->(m)
RETURN n.name, COUNT(m) AS TalksGiven
ORDER BY TalksGiven DESC LIMIT 20;

3) Find talks related by tag to specific talk and count them:

MATCH (n:Talk {name: "Michael Green: Why we should build wooden skyscrapers"})
      -[:HasTag]->(t:Tag)<-[:HasTag]-(m:Talk)
WITH * ORDER BY m.name
RETURN t.name, COLLECT(m.name), COUNT(m) AS TalksCount
ORDER BY TalksCount DESC;

4) Find 20 most frequently used tags:

MATCH (t:Tag)<-[:HasTag]-(n:Talk)
RETURN t.name AS Tag, COUNT(n) AS TalksCount
ORDER BY TalksCount DESC, Tag LIMIT 20;

5) Find 20 talks most rated as "Funny". If you want to query by other ratings, possible values are: Obnoxious, Jaw-dropping, OK, Persuasive, Beautiful, Confusing, Longwinded, Unconvincing, Fascinating, Ingenious, Courageous, Funny, Informative and Inspiring.

MATCH (r:Rating{name:"Funny"})<-[e:HasRating]-(m:Talk)
RETURN m.name, e.user_count ORDER BY e.user_count DESC LIMIT 20;

6) Find inspiring talks and their speakers from the field of technology:

MATCH (n:Talk)-[:HasTag]->(m:Tag {name: "technology"})
MATCH (n)-[r:HasRating]->(p:Rating {name: "Inspiring"})
MATCH (n)<-[:Gave]-(s:Speaker)
WHERE r.user_count > 1000
RETURN n.title, s.name, r.user_count ORDER BY r.user_count DESC;

7) Now let's see one real-world example — how to make a real-time recommendation. If you've just watched a talk from a certain speaker (e.g. Hans Rosling) you might be interested in finding more talks from the same speaker on a similar topic:

MATCH (n:Speaker {name: "Hans Rosling"})-[:Gave]->(m:Talk)
MATCH (t:Talk {title: "New insights on poverty"})-[:HasTag]->(tag:Tag)<-[:HasTag]-(m)
WITH * ORDER BY tag.name
RETURN m.title as Title, COLLECT(tag.name), COUNT(tag) as TagCount
ORDER BY TagCount DESC, Title;

The following few queries are focused on extracting information about TED events.

8) Find how many talks were given per event:

MATCH (n:Event)<-[:InEvent]-(t:Talk)
RETURN n.name as Event, COUNT(t) AS TalksCount
ORDER BY TalksCount DESC, Event
LIMIT 20;

9) Find the most popular tags in the specific event:

MATCH (n:Event {name:"TED2006"})<-[:InEvent]-(t:Talk)-[:HasTag]->(tag:Tag)
RETURN tag.name as Tag, COUNT(t) AS TalksCount
ORDER BY TalksCount DESC, Tag
LIMIT 20;

10) Discover which speakers participated in more than 2 events:

MATCH (n:Speaker)-[:Gave]->(t:Talk)-[:InEvent]->(e:Event)
WITH n, COUNT(e) AS EventsCount WHERE EventsCount > 2
RETURN n.name as Speaker, EventsCount
ORDER BY EventsCount DESC, Speaker;

11) For each speaker search for other speakers that participated in same events:

MATCH (n:Speaker)-[:Gave]->()-[:InEvent]->(e:Event)<-[:InEvent]-()<-[:Gave]-(m:Speaker)
WHERE n.name != m.name
WITH DISTINCT n, m ORDER BY m.name
RETURN n.name AS Speaker, COLLECT(m.name) AS Others
ORDER BY Speaker;