• Define
• Entity
• Relation
• Attribute
• Undefine
• Clients Guide
• Summary

Define

As the name suggests, we use the define keyword to develop the schema which represents the dataset stored in a TypeDB knowledge graph. We use define to add new entities, relations, attributes and rules to the schema.

When defining the schema in a single schema.tql file, the keyword define needs to be included only once at the very top.

We can also use the define keyword in the interactive mode of the TypeDB Console as well as the TypeDB Clients Java, Python and Node.js.

To try the following examples with one of the TypeDB clients, follows these Clients Guide.

Entity

An entity is a thing with a distinct existence in the domain. For example, organisation, location and person. The existence of each of these entities is independent of any other concept in the domain.

Define an entity

To define a new entity, we use the sub keyword followed by entity.

Assign an attribute to an entity

We can assign any number of attributes to an entity. To do so, we use the owns keyword followed by the attribute’s label.

Assign an attribute to an entity as a unique identifier

To assign a unique attribute to an entity, we use the owns keyword followed by the attribute’s label and the @key modifier.

This guarantees that no instances of email may hold the same value among all instances of person.

Entity to play a role

An entity can play a role in a relation. To define the role played by an entity, we use the plays keyword followed by the role’s label.

Subtype an entity

We can define an entity to inherit all attributes owned and roles played by another entity. Let’s look at an example of subtyping the media entity.

As you can see in the example above, when defining entities, what follows the sub keyword can be a label previously given to another entity. By subtyping a parent entity, the children inherit all attributes owned and roles played by their parent.

In this example, comment and media are both considered to be subtypes of post. Similarly video and photo are subtypes of media and so are defined that way. Therefore, although not defined explicitly, we are right to assume that comment, media, video and photo all play the roles to, in and to. However, the role attached and the attributes caption and file are played and owned only by the media entity and its subtypes. Similarly, the role to and the attribute content are played and owned only by the comment entity.

The ability to subtype entities not only helps mirror the reality of the dataset as perceived in the real world but also enables automated reasoning using type hierarchies.

Define an abstract entity

There may be scenarios where a parent entity is only defined for other entities to inherit, and under no circumstance, do we expect to have any instances of this parent. To model this logic in the schema, we use the abstract keyword. Let’s say in the example above, we would like to define both the post and media entity types to be abstract. By doing so, we are indicating that no data instances of the of these entity types are allowed to be created, leaving us only with instances of comment, photo and video.

Relation

A relation describes how two or more things are in some way connected to each other. For example, friendship and employment. Each of these relations must relate to roles that are played by something else in the domain. In other words, relations are dependent on the existence of at least two other things.

Define a relation

To define a new relation, we use the sub keyword followed by relation.

define

employment sub relation;

To complete the definition of a relation, we must determine the roles that it relates to. To do so, we use the relates keyword followed by the role’s label.

The roles employee and employer are now ready to be played by other concept types in the schema.

Role players of a relation

Entities, attributes, and even other relations can play a role in a relation. To do this we make use of the plays keyword followed by the role’s label.

We have already seen how to define an entity to play a role and soon learn how to define an attribute to play a role as well. But what about a relation that plays a role in another relation?

Define a relation to play a role

Let’s go through a simple example of how a relation can play a role in another relation.

In the example above, the friendship relation plays the role of the friendship in the friend-request relation. The other two role players in a friend-request are 1) the person who plays the requester role and 2) another person whole plays the respondent role.

Once the friend-request is accepted, then those two persons play the role of friend in the friendship relation.

A relation with many role players

A relation can relate to any number of roles. The example below illustrates a three-way relation.

In the example above, the reaction relation relates to three roles:

1. emotion role played by an emotion attribute.
2. to role played by a post entity.
3. by role played by a person entity.

Assign an attribute to a relation

We can assign any number of attributes to a relation. To do so, we use the owns keyword followed by the attribute’s label.

Assign an attribute to a relation as a unique identifier

To assign a unique attribute to a relation, we use the key keyword followed by the attribute’s label.

This guarantees that no instances of reference-id may hold the same value among all instances of employment.

Subtype a relation

We can define a relation to inherit all attributes owned, and roles related to and played by another relation. Let’s take a look at an example of subtyping a friend-request relation.

As you can see in the example above, when defining relations, what follows the sub keyword can be a label previously given to another relation. By subtyping a parent relation, the children inherit all attributes owned and roles played by their parent.

In this example, friend-request and membership-request are both considered to be subtypes of request and so are defined that way. Modelling these relations in this way, not only allows us to query for locations of birth and residence separately, but also allows us to query for all the associations that a given person has with a given location.

Note the use of the as keyword. This is necessary to determine the correspondence between the role of the child and that of the parent.

The ability to subtype relations not only helps mirror the reality of the dataset as perceived in the real world but also enables automated reasoning using type hierarchies.

Define an abstract relation

There may be scenarios where a parent relation is only defined for other relations to inherit, and under no circumstance, do we expect to have any instances of this parent. To model this logic in the schema, we use the abstract keyword. Let’s say in the example above, we would like to define the localisation relation type to be abstract. By doing so, we are indicating that no data instances of the request relation are allowed to be created, leaving us with instances of friend-request and membership-request only.

Attribute

An attribute is a piece of information that determines the property of an element in the domain. For example, name, language and age. These attributes can be assigned to anything that needs them as a property.

Define an attribute

To define a new attribute, we use the sub keyword followed by attribute, value and the type of the desired value.

The name attribute is now ready to be owned by any other type in the schema.

The data types available in a TypeDB knowledge graph are:

• long: a 64-bit signed integer.
• double: a double-precision floating point number, including a decimal point.
• string: enclosed in double " or single ' quotes
• boolean: true or false
• datetime: a date or date-time in the following formats:
  • yyyy-mm-dd
  • yyyy-mm-ddThh:mm
  • yyyy-mm-ddThh:mm:ss
  • yyyy-mm-ddThh:mm:ss.f
  • yyyy-mm-ddThh:mm:ss.ff
  • yyyy-mm-ddThh:mm:ss.fff

The same attribute can be owned by different concept types..

A concept type can have any number of the same attribute that holds different values. In other words, a concept type has a many-to-many relation with its attributes.

An instance of a person can have one instance of phone-number, or two or three, … you get the idea.

Restrict attribute’s value by Regex

Optionally, we can specify a Regex that the values of an attribute type must conform to. To do this, we use the regex keyword followed by a Java Regex Pattern.

Owners of an attribute

Entities, relations, and even attributes can own one or more attributes of their own. To do this we make use of the owns keyword followed by the attributes’s label.

We have already seen how to assign an attribute to an entity and similarly to assign an attribute to a relation. But what about an attribute owning an attribute of its own?

Assign an attribute to another attribute

Let’s go through a simple example of how an attribute can own an attribute of its own.

In this example, attribute content can be owned by, for instance, a post entity. What this example aims to showcase is that the content attribute, besides its own value, owns an attribute named language which holds the name of the language the text is written in.

Define an attribute to play a role

An attribute can play a role in a relation. To define the role played by an attribute, we use the plays keyword followed by the role’s label.

Subtype an attribute

We can define an attribute to inherit the valuetype, attributes owned and roles played by another attribute.

What this definition means is that birth-date, start-date and end-date are all inherently subtypes of event-date. They inherit the value type of event-date as well as its contextuality.

The ability to subtype attributes not only helps mirror the reality of our dataset but also enables automated reasoning using type hierarchies.

Define an abstract attribute

There may be scenarios where a parent attribute is only defined for other attributes to inherit, and under no circumstance, do we expect to have any instances of this parent. To model this logic in the schema, we use the abstract keyword. Let’s say in the example above, we would like to define the event-date attribute type to be abstract. By doing so, we are indicating that no data instances of the event-date attribute are allowed to be created, leaving us with instances of birth-date, start-date and end-date.

Undefine

As the name suggests, we use the undefine keyword to remove the definition of a type or its association with other types from the schema.

Undefine an attribute’s association

We can undefine the association that a type has with an attribute.

The query above, removes the attribute nickname from the entity person.

Undefine a relation

Undefining a relation inherently undefines all of its roles. Therefore when a relation is undefined any types that were playing roles in that relation will no longer play those roles. Given an fluency relation we can undefine it as shown below.

Undefine a Supertype

When the concept type to be undefined is a supertype to something else, we must first undefine all its subtypes before undefining the supertype itself.

Clients Guide

Summary

We learned that a TypeDB schema is essentially a collection of Entities, Relations, and Attributes - what we call the TypeDB Concept Types. It is the modularity of these concept types and how they interact with one another that allows us to model complex datasets in an intuitive way that represents their true nature.

In the next section, we learn about one last addition to the schema - TypeQL Rules.