This document discusses and compares graph data structures represented as linked data/RDF and property graphs. It provides examples of linked data/RDF graphs using Turtle syntax and JSON-LD, and how they can be queried with SPARQL. It also demonstrates how to represent the same graph data as a property graph using TinkerPop and Gremlin, and how the graph can be queried using Gremlin and Cypher languages. Key graph concepts like nodes, edges, and properties are also introduced.

1. Graph Data
Linked Data and
Property Graphs

2. Contents
● Example
● LD/RDF
● PG
● SPARQL
● Gremlin/Cypher
● BIG data
– Apache Giraph / Bulk Synchronous Processing
● Ideally?
– +arrays+URIs+attributes

3. Graphs
● A set of vertices (nodes) and edges (arcs)
● Except the useful kind have labels on edges
● … and the nodes are just dots.

4. Graphs
G = ( V , E )
V – Vertexes (Nodes)
E – Edges (Arcs, Links)

5. Graphs

6. Graphs For Information
Alice
Bob
Eve
listensTo
knows

7. Graphs For Information
Alice
... has a name “Alice Hacker”
... has an employee number

8. Linked Data / RDF
● Standards
– What it means
– Syntaxes for exchanging data
– Query language
● URI name things globally
● Uniform representation
– Link to another thing is same as link to a value
● Complex structures encoded in the basic mechanism
● “Schemaless” data integration

9. Linked Data
★ make your stuff available on the Web (whatever
format) under an open license
★★ make it available as structured data (e.g., Excel
instead of image scan of a table)
★★★ use non-proprietary formats (e.g., CSV instead
of Excel)
★★★★ use URIs to denote things, so that people
can point at your stuff
★★★★★ link your data to other data to provide context
http://5stardata.info/

10. Linked Data / RDF
http://example/alice
"Alice Hacker"
foaf:name
http://example/bob
foaf:knows
prefix person: <http://example/person/>
prefix foaf: <http://xmlns.com/foaf/0.1/>
<http://example/alice>
foaf:name "Alice Hacker" ;
foaf:knows <http://example/bob> .
<http://example/bob>
foaf:name "Bob Tester" ;
foaf:knows <http://example/alice> .
foaf:name
Bob Tester
foaf:knows

11. JSON-LD
● Links and semantics for the JSON ecosystem
{
"@context" : "http://example/person.jsonld",
"@graph" : [ {
"@id" : "http://example/alice",
"knows" : "http://example/bob",
"name" : "Alice Hacker"
}, {
"@id" : "http://example/bob",
"knows" : "http://example/alice",
"name" : "Bob Tester"
} ]
}

12. SPARQL Query
prefix person: <http://example/person/>
prefix foaf: <http://xmlns.com/foaf/0.1/>
<http://example/alice> foaf:name "Alice Hacker" ;
foaf:knows <http://example/bob> .
<http://example/bob> foaf:name "Bob Tester" ;
foaf:knows <http://example/alice> .
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?name
WHERE
{ ?person foaf:name "Alice Hacker" ;
?person foaf:knows ?name . }
----------------
| name |
================
| "Bob Tester" |
----------------

13. Property Graphs
● Separates Links and Attributes
● Nodes have attributes
– … and so do edges
● Different definitions
– https://github.com/tinkerpop/ is the de facto standard
– Not universal
● Data exchange (web publishing) is not an objective
● Analysis and schema-less data applications

14. Build
Graph graph = new TinkerGraph();
Vertex a = graph.addVertex("alice");
Vertex b = graph.addVertex("bob");
a.setProperty("name","Alice Hacker");
b.setProperty("name","Bob Coder");
Edge e1 = graph.addEdge("k1", a, b, "knows");
Edge e2 = graph.addEdge("k2", b, a, "knows") ;

15. GSON
{
"edges" : [
{
"_id" : "k1" ,
"_inV" : "bob" ,
"_label" : "knows" ,
"_outV" : "alice" ,
"_type" : "edge"
} ,
{
"_id" : "k2" ,
"_inV" : "alice" ,
"_label" : "knows" ,
"_outV" : "bob" ,
"_type" : "edge"
}
] ,
"mode" : "NORMAL" ,
"vertices" : [
{
"_id" : "bob" ,
"_type" : "vertex" ,
"name" : "Bob Coder"
} ,
{
"_id" : "alice" ,
"_type" : "vertex" ,
"name" : "Alice Hacker"
}

16. Gremlin
// Groovy to Java
@SuppressWarnings("unchecked")
Pipe<Vertex,Vertex> pipe = Gremlin.compile("g.v('alice').out('knows').name");
for(Object name : pipe) {
System.out.println((String) name);
}
g.v('alice').out('knows').name

17. Cypher Query
● Neo4J specific
● Property Graph + “labels” (= types) – node names
CREATE (alice { name: 'Alice Hacker'} ) ,
(bob { name: 'Bob Tester'} ) ,
(alice) -[:knows]-> (bob) ,
(bob) -[:knows]-> (alice)
MATCH (a)-[:knows]->x
WHERE a.name = 'Alice Hacker'
RETURN x.name