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 |