Crate gdl[−][src]
Expand description
Graph Definition Language (GDL)
Inspired by the Neo4j Cypher query language, GDL allows the simple definition of property graphs. GDL contains a parser and simple structs that represent the property graph and its elements. The Rust implementation is inspired by my Java implementation.
Property graph data model
A property graph consists of nodes and relationships. Nodes have zero or more labels, relationships have zero or one relationship type. Both, nodes and relationships have properties, organized as key-value-pairs. Relationships are directed, starting at a source node and pointing at a target node.
Quickstart example
use gdl::{CypherValue, Graph}; use std::rc::Rc; let gdl_string = "(alice:Person { name: 'Alice', age: 23 }), (bob:Person { name: 'Bob', age: 42 }), (alice)-[r:KNOWS { since: 1984 }]->(bob)"; let graph = gdl_string.parse::<gdl::Graph>().unwrap(); assert_eq!(graph.node_count(), 2); assert_eq!(graph.relationship_count(), 1); let alice = graph.get_node("alice").unwrap(); assert_eq!(alice.property_value("age"), Some(&CypherValue::from(23))); assert_eq!(alice.property_value("name"), Some(&CypherValue::from("Alice"))); let relationship = graph.get_relationship("r").unwrap(); assert_eq!(relationship.rel_type(), Some("KNOWS"));
More GDL language examples
Define a node:
let g = "()".parse::<gdl::Graph>().unwrap(); assert_eq!(g.node_count(), 1);
Define a node and assign it to variable alice
:
let g = "(alice)".parse::<gdl::Graph>().unwrap(); assert!(g.get_node("alice").is_some());
Define a node with label User
and multiple properties:
let g = "(alice:User { name: 'Alice', age : 23 })".parse::<gdl::Graph>().unwrap(); assert_eq!(g.get_node("alice").unwrap().labels().collect::<Vec<_>>(), vec!["User"]); assert!(g.get_node("alice").unwrap().property_value("name").is_some()); assert!(g.get_node("alice").unwrap().property_value("age").is_some());
Define an outgoing relationship:
let g = "(alice)-->()".parse::<gdl::Graph>().unwrap(); assert_eq!(g.relationship_count(), 1);
Define an incoming relationship:
let g = "(alice)<--()".parse::<gdl::Graph>().unwrap(); assert_eq!(g.relationship_count(), 1);
Define a relationship with type KNOWS
, assign it to variable r1
and add a property:
use std::rc::Rc; let g = "(alice)-[r1:KNOWS { since : 2014 }]->(bob)".parse::<gdl::Graph>().unwrap(); assert!(g.get_relationship("r1").is_some()); assert_eq!(g.get_relationship("r1").unwrap().rel_type(), Some("KNOWS"));
Define multiple outgoing relationships from the same source node (i.e. alice
):
let g = " (alice)-[r1:KNOWS { since : 2014 }]->(bob) (alice)-[r2:KNOWS { since : 2013 }]->(eve) ".parse::<gdl::Graph>().unwrap(); assert_eq!(g.node_count(), 3); assert_eq!(g.relationship_count(), 2);
Define paths (four nodes and three relationships are created):
let g = "()-->()<--()-->()".parse::<gdl::Graph>().unwrap(); assert_eq!(g.node_count(), 4); assert_eq!(g.relationship_count(), 3);
Paths can be comma separated to express arbitrary complex patterns:
let g = " ()-->()<--()-->(), ()<--()-->()-->(), ()-->()<--()-->() ".parse::<gdl::Graph>().unwrap(); assert_eq!(g.node_count(), 12); assert_eq!(g.relationship_count(), 9);
License
Apache 2.0 or MIT