Cayley is an open-source graph inspired by the graph database behind [Freebase](http://freebase.com) and Google's [Knowledge Graph](https://en.wikipedia.org/wiki/Knowledge_Graph).
Its goal is to be a part of the developer's toolbox where [Linked Data](http://linkeddata.org/) and graph-shaped data (semantic webs, social networks, etc) in general are concerned.
[](https://quay.io/repository/barakmich/cayley)
* [MongoDB](https://www.mongodb.org) for distributed stores
* In-memory, ephemeral
* Modular design; easy to extend with new languages and backends
* Good test coverage
* Speed, where possible.
Rough performance testing shows that, on consumer hardware and an average disk, 134m quads in LevelDB is no problem and a multi-hop intersection query -- films starring X and Y -- takes ~150ms.
\* Note that while it's not exactly Gremlin, it certainly takes inspiration from that API. For this flavor, [see the documentation](docs/GremlinAPI.md).
## Getting Started
Grab the latest [release binary](https://github.com/google/cayley/releases) and extract it wherever you like.
If you prefer to build from source, see the documentation on the wiki at [How to start hacking on Cayley](https://github.com/google/cayley/wiki/How-to-start-hacking-on-Cayley) or type
```
mkdir -p ~/cayley && cd ~/cayley
export GOPATH=`pwd`
export PATH=$PATH:~/cayley/bin
mkdir -p bin pkg src/github.com/google
cd src/github.com/google
git clone https://github.com/google/cayley
cd cayley
go get github.com/tools/godep
godep restore
go build ./cmd/cayley
```
Then `cd` to the directory and give it a quick test with:
```
./cayley repl --dbpath=data/testdata.nq
```
To run the web frontend, replace the "repl" command with "http"
```
./cayley http --dbpath=data/testdata.nq
```
You should see a `cayley>` REPL prompt. Go ahead and give it a try:
```
// Simple math
cayley> 2 + 2
// JavaScript syntax
cayley> x = 2 * 8
cayley> x
// See all the entities in this small follow graph.
cayley> graph.Vertex().All()
// See only dani.
cayley> graph.Vertex("dani").All()
// See who dani follows.
cayley> graph.Vertex("dani").Out("follows").All()
```
**Running the visualizer on the web frontend**
To run the visualizer: click on visualize and enter:
For somewhat more interesting data, a sample of 30k movies from Freebase comes in the checkout.
```
./cayley repl --dbpath=data/30kmoviedata.nq.gz
```
To run the web frontend, replace the "repl" command with "http"
```
./cayley http --dbpath=data/30kmoviedata.nq.gz
```
And visit port 64210 on your machine, commonly [http://localhost:64210](http://localhost:64210)
## Running queries
The default environment is based on [Gremlin](http://gremlindocs.com/) and is simply a JavaScript environment. If you can write jQuery, you can query a graph.
You'll notice we have a special object, `graph` or `g`, which is how you can interact with the graph.
The simplest query is merely to return a single vertex. Using the 30kmoviedata.nq dataset from above, let's walk through some simple queries:
```javascript
// Query all vertices in the graph, limit to the first 5 vertices found.
graph.Vertex().GetLimit(5)
// Start with only one vertex, the literal name "Humphrey Bogart", and retrieve all of them.
graph.Vertex("Humphrey Bogart").All()
// `g` and `V` are synonyms for `graph` and `Vertex` respectively, as they are quite common.
g.V("Humphrey Bogart").All()
// "Humphrey Bogart" is a name, but not an entity. Let's find the entities with this name in our dataset.
// Follow links that are pointing In to our "Humphrey Bogart" node with the predicate "name".
g.V("Humphrey Bogart").In("name").All()
// Notice that "name" is a generic predicate in our dataset.
// Starting with a movie gives a similar effect.
g.V("Casablanca").In("name").All()
// Relatedly, we can ask the reverse; all ids with the name "Casablanca"
g.V().Has("name", "Casablanca").All()
```
You may start to notice a pattern here: with Gremlin, the query lines tend to:
Start somewhere in the graph | Follow a path | Run the query with "All" or "GetLimit"
A container exposing the HTTP API of cayley is available.
To run the container one must first setup a data directory that contains the configuration file and optionally contains persistent files (i.e. a boltdb database file).
```
mkdir data
cp my_config.cfg data/cayley.cfg
docker run -v $PWD/data:/data -p 64321:64321 -d quay.io/barakmich/cayley
Not a Google project, but created and maintained [by a Googler](https://github.com/barakmich), with permission from and assignment to Google, under the [Apache License, version 2.0](http://www.apache.org/licenses/LICENSE-2.0).
## Contact
* Email list: [cayley-users at Google Groups](https://groups.google.com/forum/?hl=en#!forum/cayley-users)
