XBRL Schemas

XBRL Schemas are XML Schema Definition (.xsd) files that define concepts -- the data elements that can be reported in instance documents.

What a Schema Defines

Each concept (element) in a schema has these key attributes:

Attribute	Purpose	Example
name	Identifier for the concept	Revenue
id	Unique ID within the schema	ifrs_Revenue
type	Data type	xbrli:monetaryItemType
substitutionGroup	Must be xbrli:item or xbrli:tuple	xbrli:item
periodType	instant or duration	duration
balance	debit or credit (monetary items only)	credit
abstract	If true, cannot hold data (structural only)	false
nillable	Whether nil values are allowed	true

Common Data Types

Type	Use
xbrli:monetaryItemType	Currency amounts (Revenue, Assets)
xbrli:stringItemType	Text (descriptions, names)
xbrli:dateItemType	Dates
xbrli:booleanItemType	True/false values
xbrli:integerItemType	Whole numbers
xbrli:decimalItemType	Decimal numbers
xbrli:sharesItemType	Share counts
xbrli:pureItemType	Dimensionless numbers (ratios, percentages)

Period Types

• instant -- Point-in-time values (e.g., balance sheet items like Assets, Liabilities)
• duration -- Values over a time range (e.g., income statement items like Revenue, Expenses)

Example from the LEI Taxonomy

<xsd:element name="LEI"
  id="lei_LEI"
  substitutionGroup="xbrli:item"
  nillable="true"
  xbrli:periodType="duration"
  type="lei:leiItemType" />

This defines a concept called LEI that:

• Is an item (can hold a value)
• Has period type duration
• Uses a custom type leiItemType (a 20-character alphanumeric string)

Schema References

Schemas reference linkbases via <link:linkbaseRef> elements in the annotation section:

<xsd:annotation>
  <xsd:appinfo>
    <link:linkbaseRef xlink:href="labels.xml"
      xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef"
      xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase"/>
  </xsd:appinfo>
</xsd:annotation>

Schema Imports

Schemas can import other schemas to build on existing taxonomies:

<xsd:import namespace="http://www.xbrl.org/2003/instance"
  schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>

This is how extension taxonomies build on base taxonomies -- the CIPC taxonomy imports the IFRS taxonomy this way.