property-graph
v3.0.0
Published
Base for creating objects that behave like a Property Graph.
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property-graph
Extensible base for creating objects that behave like a Property Graph.
Overview
The property-graph
package is intended as a foundation for libraries requiring many custom types of compatible parts, which can be represented as a Property Graph. The Property Graph representation is useful for dependency chains, resource references, node-based art workflows, and a broader class of applications where Graph databases are common.
Conceptually, a Property Graph is a labeled, directed multigraph, in which entities ("nodes") may have named relationships ("edges") with other nodes on the graph. Both nodes and edges may also be associated with key/value attributes. Beyond that, property-graph
is intended to be small and practical, rather than providing a large standard library for graph theory — if you need something more comprehensive, I'd suggest graphology
.
Typically, you'll define several classes inheriting from the base GraphNode
. When using TypeScript, an interface should be provided defining the kinds of connections that each type of graph node allows. Then, .set
and .get
methods may be used to set key/value attributes (strings, numbers, booleans, ...), and .getRef
and .setRef
methods may be used to create edges (or relationships) to other nodes of a compatible type. All references have names, and support compile-time type-checking.
Features
In a codebase with many distinct types of entities and relationships among them (e.g. "Client has N Projects", "Project has N Tasks"), this project can make management of entities and their relationships considerably easier than writing plain getters/setters for each case.
- Traversal: GraphEdges are tracked and can be traversed up or down
- Disposal: GraphNode disposal automatically cleans up incoming references from other nodes
- Finding dependents: Efficiently locate all GraphNodes that refer to a given GraphNode, or that have references from a given GraphNode
- Change detection: GraphNodes dispatch events when changed, which can be optionally propagated throughout the graph
- Extensibility: Operations like
.copy()
,.equals()
, and.swap(a, b)
can be implemented abstractly
Usage
Definitions:
import { GraphNode, RefSet } from 'property-graph';
interface IPerson {
name: string;
age: number;
friends: RefSet<Person>;
pet: Pet;
}
interface IPet {
type: 'dog' | 'cat';
name: string;
}
class Person extends GraphNode<IPerson> {
getDefaults(): Nullable<IPerson> {
return {name: '', age: 0, friends: new RefSet(), pet: null};
}
}
class Pet extends GraphNode<IPet> {
getDefaults(): Nullable<IPet> {
return {type: 'dog', name: ''};
}
}
Basic usage:
const graph = new Graph();
const spot = new Pet(graph)
.set('type', 'dog')
.set('name', 'Spot');
const jo = new Person(graph)
.set('name', 'Jo')
.set('age', 41)
.setRef('pet', spot);
const sam = new Person(graph)
.set('name', 'Sam')
.set('age', 45)
.addRef('friends', jo);
Lifecycles:
jo.equals(sam); // recursive equality → false
console.log(sam.listRefs('friends')); // → [jo]
jo.dispose();
console.log(sam.listRefs('friends')); // → []
API
Literal Attributes
Literal attributes (string, number, boolean, ...) are modified with two methods:
node.get('key'): Literal
node.set('key', value: Literal): this
References
References support one named connection to a single graph node of a given type:
node.getRef('key'): GraphNode
node.setRef('key', node: GraphNode): this
Reference Lists
Reference Lists support a named list of connections to graph nodes of a given type:
node.addRef('key', node: GraphNode): this
node.removeRef('key', node: GraphNode): this
node.listRefs('key'): GraphNode[]
Reference Maps
Reference Maps support a named map having any number of subkeys, where each subkey points to a graph node of a given type:
node.getRefMap('key', 'subkey'): GraphNode
node.setRefMap('key', 'subkey', node: GraphNode): this
node.listRefMapKeys('key'): string[]
node.listRefMapValues('key'): GraphNode[]