Grakn Node.js Client

A Node.js client for Grakn

Requires Grakn 1.3.0 && Node >= 6.5.0

Installation

To install the Grakn client, simply run:

npm install grakn

You will also need access to a Grakn database. Head here to get started with Grakn.

Quickstart

Begin by importing Grakn:

const Grakn = require('grakn');

Now you can create a new session and open a new Grakn transaction:

const grakn = new Grakn('localhost:48555');
const session = grakn.session('keyspace');
const tx = await session.transaction(Grakn.txType.WRITE);

Execute Graql query (this example works inside an async function):

const resultIterator = await tx.query("match $x isa person; limit 10; get;"); // This will return an Iterator of ConceptMap Answer
const answer = await resultIterator.next(); // Take first ConceptMap Answer
const person = answer.map().get('x'); // Access map in Answer with answer.map() and take Concept associated to variable x from 'match $x isa person; get;'
tx.close();

API Reference

First create a new Grakn object with

// URI must be a string containing host address and gRPC port of a running Grakn instance, e.g. "localhost:48555"
const grakn = new Grakn(URI);

on the Grakn object the following methods are available:

Grakn

Method	Return type	Description
session(String keyspace)	Session	Return a new Session bound to the specified keyspace
async keyspaces().delete(String keyspace)	void	Deletes the specified keyspace
async keyspaces().retrieve()	Array of String	Retrieves all available keyspaces

on the Session the following methods are available:

Session

Method	Return type	Description
async transaction(Grakn.txType)	Transaction	Return a new Transaction bound to the keyspace of this session
close()	void	This must be used to correctly terminate session and close communication with server.

Once obtained a Transaction you will be able to:

Transaction

Method	Return type	Description
async query(String graqlQuery[, { infer }])	Iterator of Answer	Executes a Graql query on the session keyspace. It's possible to specify whether to enable inference passing an object with infer property set to true or false. Inference is ON by default.
async commit()	void	Commit current Transaction, persisting changes in the graph. After committing, the transaction will be closed and you will need to get a new one from the session
async close()	void	Closes current Transaction without committing. This makes the transaction unusable.
async getConcept(String conceptId)	Concept or null	Retrieves a Concept by ConceptId
async getSchemaConcept(String label)	SchemaConcept or null	Retrieves a SchemaConcept by label
async getAttributesByValue(attributeValue, Grakn.dataType)	Iterator of Attribute	Get all Attributes holding the value provided, if any exists
async putEntityType(String label)	EntityType	Create a new EntityType with super-type entity, or return a pre-existing EntityType with the specified label
async putRelationshipType(String label)	RelationshipType	Create a new RelationshipType with super-type relation, or return a pre-existing RelationshipType with the specified label
async putAttributeType(String label, Grakn.dataType)	AttributeType	Create a new AttributeType with super-type attribute, or return a pre-existing AttributeType with the specified label and DataType
async putRole(String label)	Role	Create a Role, or return a pre-existing Role, with the specified label.
async putRule(String label, String when, String then)	Rule	Create a Rule, or return a pre-existing Rule, with the specified label

Iterator

Some of the following Concept methods return an Iterator, on every iterator the following methods are available:

Method	Return type	Description
async next()	IteratorElement or null	Retrieves next element or returns null when no more elements are available
async collect()	Array of IteratorElement	Consumes the iterator and collect all the elements into an array
async collectConcepts()	Array of Concept	Consumes the iterator and return array of Concepts. This helper is only available on Iterator containing ConceptMap Answer, returned by transaction.query().. It is useful when one wants to work directly on Concepts without the need to traverse the result map or access the explanation.

IteratorElement

Element handled by iterators, depending on the type of iterator this can be a type of Concept or an Answer.

Answer

This object represents a query answer and it is contained in the Iterator returned by transaction.query() method.
There are different types of Answer, based on the type of query executed a different type of Answer will be returned:

Query Type	Answer Type
define	ConceptMap
undefine	ConceptMap
get	ConceptMap
insert	ConceptMap
delete	ConceptMap
aggregate count/min/max/sum/mean/std	Value
aggregate group	AnswerGroup
compute count/min/max/sum/mean/std	Value
compute path	ConceptList
compute cluster	ConceptSet
compute centrality	ConceptSetMeasure

ConceptMap

Method	Return type	Description
map()	Map<String, Concept>	Returns result map in which every variable name (key) is linked to a Concept.
explanation()	Explanation or null	Returns an Explanation object if the current Answer contains inferred Concepts, null otherwise.

Value

Method	Return type	Description
number()	Number	Returns numeric value of the Answer.
explanation()	Explanation or null	Returns an Explanation object if the current Answer contains inferred Concepts, null otherwise.

ConceptList

Method	Return type	Description
list()	Array of String	Returns list of Concept IDs.
explanation()	Explanation or null	Returns an Explanation object if the current Answer contains inferred Concepts, null otherwise.

ConceptSet

Method	Return type	Description
set()	Set of String	Returns a set containing Concept IDs.
explanation()	Explanation or null	Returns an Explanation object if the current Answer contains inferred Concepts, null otherwise.

ConceptSetMeasure

Method	Return type	Description
measurement()	Number	Returns numeric value that is associated to the set of Concepts contained in the current Answer.
set()	Set of String	Returns a set containing Concept IDs.
explanation()	Explanation or null	Returns an Explanation object if the current Answer contains inferred Concepts, null otherwise.

AnswerGroup

Method	Return type	Description
owner()	Concept	Returns the Concepts which is the group owner.
answers()	Array of Answer	Returns list of Answers that belongs to this group.
explanation()	Explanation or null	Returns an Explanation object if the current Answer contains inferred Concepts, null otherwise.

Explanation

Method	Return type	Description
queryPattern()	String	Returns a query pattern that describes how the owning answer was retrieved.
answers()	Array of Answer	Set of deducted/factual answers that allowed us to determine that the owning answer is true

Concepts hierarchy

Grakn is composed of different types of Concepts, that have a specific hierarchy

                                                Concept
                                                /       \
                                              /           \
                                            /               \
                                          /                   \
                                  SchemaConcept                    Thing
                                  /     |    \                    /   |  \
                                /       |     \                 /     |    \
                              /         |      \              /       |      \
                            Type      Rule    Role     Entity    Attribute   Relationship
                        /     |   \
                      /       |     \
                    /         |       \
            EntityType  AttributeType  RelationshipType

---

All Concepts are bound to the transaction that has been used to retrieve them. If for any reason a trasaction gets closed all the concepts bound to it won't be able to communicate with the database anymore, so all the methods won't work and the user will have to re-query for the needed concepts.

---

Concept

These methods are available on every type of Concept

Method	Return type	Description
async delete()	void	Delete concept
isSchemaConcept()	Boolean	Check whether this Concept is a SchemaConcept
isType()	Boolean	Check whether this Concept is a Type
isThing()	Boolean	Check whether this Concept is a Thing
isAttributeType()	Boolean	Check whether this Concept is an AttributeType
isEntityType()	Boolean	Check whether this Concept is an EntityType
isRelationshipType()	Boolean	Check whether this Concept is a RelationshipType
isRole()	Boolean	Check whether this Concept is a Role
isRule()	Boolean	Check whether this Concept is a Rule
isAttribute()	Boolean	Check whether this Concept is an Attribute
isEntity()	Boolean	Check whether this Concept is a Entity
isRelationship()	Boolean	Check whether this Concept is a Relationship

Schema concept

A SchemaConcept concept has all the Concept methods plus the following:

Method	Return type	Description
async label()	String	Get label of this SchemaConcept
async label(String value)	void	Set label of this SchemaConcept
async isImplicit()	Boolean	Returns true when the SchemaConcept is implicit, i.e. when it's been created by Grakn and not explicitly by the user, false when explicitly created by the user.
async sup(Type)	void	Set direct super SchemaConcept of this SchemaConcept
async sup()	SchemaConcept or null	Get direct super SchemaConcept of this SchemaConcept
async subs()	Iterator of SchemaConcept	Get all indirect subs of this SchemaConcept.
async sups()	Iterator of SchemaConcept	Get all indirect sups of this SchemaConcept.

Thing

A Thing concept has all the Concept methods plus the following:

Method	Return type	Description
async isInferred()	Boolean	Returns true if this Thing is inferred by Reasoner, false otherwise
async type()	Type	Returns a Type which is the type of this Thing. This Thing is an instance of that type.
async relationships(...Role)	Iterator of Relationship	Returns Relationships which this Thing takes part in, which may optionally be narrowed to a particular set according to the Roles you are interested in
async attributes(...AttributeType)	Iterator of Attribute	Returns Attributes attached to this Thing, which may optionally be narrowed to a particular set according to the AttributeTypes you are interested in
async roles()	Iterator of Role	Returns the Roles that this Thing is currently playing
async keys(...Attributetype)	Iterator of Attribute	Returns a collection of Attribute attached to this Thing as a key, which may optionally be narrowed to a particular set according to the AttributeTypes you are interested in
async has(Attribute)	void	Attaches the provided Attribute to this Thing
async unhas(Attribute)	void	Removes the provided Attribute from this Thing

Attribute

An Attribute concept has all the Thing methods plus the following:

Method	Return type	Description
async value()	String	Get value of this Attribute
async owners()	Iterator of Thing	Returns the set of all Things that possess this Attribute

Relationship

A Relationship concept has all the Thing methods plus the following:

Method	Return type	Description
async rolePlayersMap()	Map<Role, Set<Thing>>	Returns a Map that links all the Roles of this Relationship to all the Things that are playing each Role
async rolePlayers(...Role)	Iterator of Thing	Returns a list of every Thing involved in this Relationship, optionally filtered by Roles played
async assign(Role, Thing)	void	Expands this Relationship to include a new role player (Thing) which is playing a specific Role
async unassign(Role, Thing)	void	Removes the Thing which is playing a Role in this Relationship.

NB: There are no specific methods for `Entity` concept.

Type

A Type concept has all the SchemaConcept methods plus the following:

Method	Return type	Description
async isAbstract(Boolean)	void	Sets the Type to be abstract - which prevents it from having any instances
async isAbstract()	Boolean	Returns true if the type is set to abstract, false otherwise
async playing()	Iterator of Role	Returns all the Roles which instances of this Type can indirectly play
async plays(Role)	void	Add a new Role to the ones that the instances of this Type are allowed to play
async attributes()	Iterator of AttributeType	The AttributeTypes which this Type is linked with.
async instances()	Iterator of Thing	Get all indirect instances of this Type
async keys()	Iterator of AttributeType	The AttributeTypes which this Type is linked with as a key
async key(AttributeType)	void	Creates an implicit RelationshipType which allows this Type and a AttributeType to be linked in a strictly one-to-one mapping.
async has(AttributeType)	void	Add a new AttributeType which the instances of this Type are allowed to have attached to themselves
async unplay(Role)	void	Delete a Role from the ones that the instances of this Type are allowed to play
async unhas(AttributeType)	void	Delete AttributeType from the ones that the instances of this Type are allowed to have attached to themselves
async unkey(AttributeType)	void	Delete AttributeType from available keys

AttributeType

An AttributeType concept has all the Type methods plus the following:

Method	Return type	Description
async create(value)	Attribute	Create new Attribute of this type with the provided value. The value provided must conform to the DataType specified for this AttributeType
async attribute(value)	Attribute or null	Retrieve the Attribute with the provided value if it exists
async dataType()	String	Get the data type to which instances of the AttributeType must have
async regex()	String or null	Retrieve the regular expression to which instances of this AttributeType must conform to, or null if no regular expression is set
async regex(String regex)	void	Set the regular expression that instances of the AttributeType must conform to

RelationshipType

A RelationshipType concept has all the Type methods plus the following:

Method	Return type	Description
async create()	Relationship	Creates and returns a new Relationship instance, whose direct type will be this type
async roles()	Iterator of Role	Returns a list of the RoleTypes which make up this RelationshipType
async relates(Role)	void	Sets a new Role for this RelationshipType
async unrelate(Role)	void	Delete a Role from this RelationshipType

EntityType

An EntityType concept has all the Type methods plus the following:

Method	Return type	Description
async create()	Entity	Creates and returns a new Entity instance, whose direct type will be this type

Role

A Role concept has all the SchemaConcept methods plus the following:

Method	Return type	Description
async relationships()	Iterator of RelationshipType	Returns the RelationshipTypes that this Role takes part in.
async players()	Iterator of Type	Returns a collection of the Types that can play this Role

Rule

A Rule concept has all the SchemaConcept methods plus the following:

Method	Return type	Description
async getWhen()	String	Retrieves the when part of this Rule. When this query is satisfied the "then" part of the rule is executed
async getThen()	String	Retrieves the then part of this Rule. This query is executed when the "when" part of the rule is satisfied