# clownface
[](https://travis-ci.org/rdf-ext/clownface)
[](https://npm.im/clownface)
Clownface is a graph traversal library inspired by [Gremlin](http://tinkerpop.apache.org/)
which allows to query any [RDF dataset](https://rdf.js.org/dataset-spec/) in a concise and readable way.
## Introduction
Querying an RDF graph can be challenging. Apart from trivial queries, e.g. simply listing all the
objects connected to a subject, it is usually necessary to write multiple loop and validation
conditions to retrieve an answer. Clownface is there to help.
## Getting started
The package is installed from npm:
```
npm i -S clownface
```
To start using it, an instance of [RDF/JS `DatasetCore`](https://rdf.js.org/dataset-spec/#datasetcore-interface) must be
provided to the exported factory method
```js
const rdf = require('@zazuko/env-bundle')
const firstName = rdf.namedNode('http://xmlns.com/foaf/0.1/firstName')
const lastName = rdf.namedNode('http://xmlns.com/foaf/0.1/lastName')
// initialize
const ptr = rdf.clownface()
// add some resources
ptr
.namedNode('http://example.com/person/stuart-bloom')
.addOut(firstName, 'Stuart')
.addOut(lastName, 'Bloom')
.namedNode('http://example.com/person/penny')
.addOut(firstName, 'Penny')
// and now retrieve the first names of those who have a last name
ptr
.has(lastName)
.out(firstName)
.values
```
## Details
At the core of clownface sits an object called a "graph pointer". A graph pointer can be backed by zero or more RDF/JS terms. It is being created by calling the function exported by the packages's default module.
The current context node or nodes can be accessed by `term`/`value` and `terms`/`values` pairs of properties. The first pair return only a single RDF/JS and its string value. They will return `undefined` if the context points at 0 or >1 nodes. The second pair of properties always return an array of the context terms and their string values.
Graph pointers provides a set of chainable methods. The most important ones are `.in(predicate)` and `.out(predicate)` which allow the traversal through the graph. It is possible to chain as many of these methods to extract a sub-graph from the available dataset.
## More examples
Check out the [deep dive](deep-dive.md) and other pages for a running examples which show how to use the graph pointer to traverse and manipulate RDF graphs.
We use the well known `` `` `