Schema.schema.md

Schema

Model for a template's schema descriptor.

Typically defined using a schema.json file within a template's file structure. All properties are currently defined by the frictionless table schema however, fields and fields.constraints are customised implementations for the project.

Type: object

Property	Type	Required	Possible values	Description
fields	array	✅	Field	Frictionless reference. An array where each entry in the array is a field descriptor.
primaryKey	string or null		string	Used by frictionless, currently only supporting single values, contains the name of a field that effectively gets set to required: true and unique, and can provide reference for foreign keys when used in a Data Package.
foreignKeys	array or null		object	Used by frictionless, a foreign key is a reference where values in a field (or fields) on the table (‘resource’ in data package terminology) described by this Table Schema connect to values a field (or fields) on this or a separate table (resource). They are directly modelled on the concept of foreign keys in SQL.

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Definitions

Constraints

The constraints of a schema field.

Currently all defined below are a subset of those available from frictionless.

Type: object

Property	Type	Required	Possible values	Description
required	boolean	✅	boolean	Indicates whether this field cannot be null. If required is false (the default), then null is allowed.
unique	boolean or null		boolean	If true, then all values for that field MUST be unique within the data file in which it is found.
minimum	integer or number or null		integer and/or number	Specifies a minimum value for a field. This is different to minLength which checks the number of items in the value. A minimum value constraint checks whether a field value is greater than or equal to the specified value. The range checking depends on the type of the field. If a minimum value constraint is specified then the field descriptor MUST contain a type key.
maximum	integer or number or null		integer and/or number	As for minimum, but specifies a maximum value for a field.
enum	array or null		string	The value of the field must exactly match a value in the enum array.

Field

Field model of a schema.

The properties of a field consisting of those properties used by frictionless for performing validations as well as extras to assist with the looking up of vocabularies when mapping as well as assisting with the creation of instruction documentation. Frictionless reference.

Type: object

Property	Type	Required	Possible values	Description
name	string	✅	string	Required by frictionless. The field descriptor MUST contain a name property. This property SHOULD correspond to the name of field/column in the data file (if it has a name). As such it SHOULD be unique (though it is possible, but very bad practice, for the data file to have multiple columns with the same name). name SHOULD NOT be considered case sensitive in determining uniqueness. However, since it should correspond to the name of the field in the data file it may be important to preserve case.
title	string	✅	string	Frictionless reference. A human readable label or title for the field.
description	string	✅	string	Frictionless reference. A description for this field e.g. "The recipient of the funds".
type	string	✅	string	Frictionless reference. type and format properties are used to give the type of the field. A fields type property is a string indicating the type of this field.
format	string or null	✅	string	Frictionless reference. type and format properties are used to give the type of the field. A field's format property is a string, indicating a format for the field type.
constraints	object	✅	Constraints
example	string or null		string	Frictionless reference. An example value of the field
url	string or null		Format: uri	The IRI of the field's concept.
vocabularies	array		string	Optional list of vocabulary IDs, defined internally within the project. Provided IDs need to have been registered to be valid. See abis_mapping.vocabs.