Practical 9

Aim : Execute queries in the Neo4j graph database and in Gephi tool perform the operations of loading csv data, running graph statistics scripts and displaying various graphical layouts.

Theory: 

What is graph data?

Graph data science is linked to data science, where connexions are first-class people, and a stronger, more detailed forecast can be made using the ties between the data points.

How graph data is stored? and how it is represented?

Graph data is contained in storage files, each of which includes data, such as nodes, associations, labels and properties, for a certain part of the graph. A data graph is a graphic display of knowledge from which we can more readily interpret similarities and patterns quickly.

How to visualize graph data and devise conclusion/result?

By looking at the graph correctly, we can imagine graph data and we can get the successful knowledge that shows mechanisms that might be present in the graphs and assist the user to understand that.

Neo4j is an open-source, NoSQL, native graph database that provides an ACID-compliant transactional backend for your applications. This means that the data is stored exactly as you whiteboard it, and the database uses pointers to navigate and traverse the graph.

Neo4j uses property graphs to extract added value of data of any company with great performance and in an agile, flexible and scalable way. 1. Performance: Graph databases such as Neo4j perform better than relational (SQL) and non-relational (NoSQL) databases.

Let's get started with Neo4j database!!

You can download Neo4j according to your system requirement from here. Although here I am going to use online Neo4j Sandbox for demo purpose.

1. First of all sign up for the No4j sandbox.

2. After successful login, you will be asked to create or launch a existing project. Here I am going to use pre built "Movies" project.

Find

Example queries for finding individual nodes.

1. Click on any query example
2. Run the query from the editor
3. Notice the syntax pattern
4. Try looking for other movies or actors

Query

Finding patterns within the graph.

1. Actors are people who acted in movies
2. Directors are people who directed a movie
3. What other relationships exist?

Create

To the right is a giant code block containing a single Cypher query statement composed of multiple CREATE clauses. This will create the movie graph.

1. Click on the code block
2. Notice it gets copied to the editor above ↑
3. Click the editor's play button to execute
4. Wait for the query to finish

Solve

You've heard of the classic "Six Degrees of Kevin Bacon"? That is simply a shortest path query called the "Bacon Path".

1. Variable length patterns
2. Built-in shortestPath() algorithm

Let's get started with Gephi!!

What is Gephi?

Gephi is an open-source network analysis and visualization software package written in Java on the NetBeans platform. Gephi is a visualization and exploration software for graphs and networks. Think Photoshop, but for graph data. Gephi is open-source, free to download, and runs on Windows, Mac OS X, and Linux.

1. Install Gephi from here.

2. Start Gephi and select a sample project for demo purpose.

3. Now you can see the graph window.

If you cannot see the graph window, you can enable it from Window->Graphs in menu bar.

4. Using direct selection tool you can highlight all the nodes directly connected to the selected node.

5. Explore different tools from the graph tool palette

6. Loading graph data in Gephi.

Gephi support CSV file format to import data. You can import nodes using node table, edges using edge table, nodes and edges using adjacency list and adjacency matrix.

For example :

The sample below shows a node table of of three nodes. The column of node identifiers must be named “Id”.
Id A B C

The sample below shows an edge table of of two edge. The columns must be named “Source” and “Target”.
Source,Target A,B C,A

The sample below shows an adjacency list of 6 edges and 4 nodes.
q,w,e,r w,q,e,r

The sample below shows an adjacency matrix of 2 edges and 2 nodes.
,Z,X Z,0,1 X,1,0

Now creating the above mentioned CSV file and importing it to Gephi.

Importing nodes

Importing edges

Importing adjacency list

Importing adjacency matrix

Final Graph

Final edge table

These are the various ways to store and load graph dataset in Gephi.

References:

https://neo4j.com/developer/graph-database/
https://gephi.org/users/supported-graph-formats/spreadsheet/