XBRL Linkbases

Linkbases are XML documents that define relationships between concepts and between concepts and resources. They are a core part of taxonomies, built using the XLink standard.

The Five Standard Linkbase Types

1. Label Linkbase

Purpose: Provides human-readable names for concepts.

• Supports multiple languages (English, French, Afrikaans, etc.) for the same concept
• Supports multiple label types per concept:

Label Role	Use
label	Standard/default label
terseLabel	Short/abbreviated label
verboseLabel	Long descriptive label
documentation	Explanatory text (like a tooltip)
periodStartLabel	Label for opening balance context
periodEndLabel	Label for closing balance context
totalLabel	Label when used as a total
negatedLabel	Label when sign is reversed

Example from LEI taxonomy:

<link:label xml:lang="en">Legal Entity Identifier</link:label>
<link:label xlink:role=".../documentation" xml:lang="en">
  Legal Entity Identifier (LEI) for the reporting entity.
</link:label>

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2. Presentation Linkbase

Purpose: Defines the tree structure for displaying concepts in a report.

• Parent-child hierarchies organise concepts into sections
• order attribute controls display sequence
• preferredLabel can specify which label type to use in a given position

Example structure:

Statement of Financial Position [abstract]
├── Assets [abstract]
│   ├── Current Assets
│   │   ├── Cash and Cash Equivalents
│   │   ├── Trade Receivables
│   │   └── Inventories
│   └── Non-Current Assets
│       ├── Property, Plant and Equipment
│       └── Intangible Assets
└── Equity and Liabilities [abstract]
    ├── Equity
    └── Liabilities

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3. Calculation Linkbase

Purpose: Defines arithmetic validation rules (addition and subtraction only).

• Uses weight attribute: +1 for addition, -1 for subtraction
• Validates that totals equal the sum of their components

Example:

Assets (total)
├── Current Assets (weight = +1)
└── Non-Current Assets (weight = +1)

→ Validation: Assets = Current Assets + Non-Current Assets

Limitations:

• Only supports summation (no multiplication, division, or conditional logic)
• For complex validation, use 14 XBRL Formula

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4. Definition Linkbase

Purpose: Defines various structural relationships, most importantly for dimensions.

Key arcroles:

Arcrole	Meaning
general-special	Genus-species (is-a) relationship
essence-alias	Concepts covering same subject matter
requires-element	One concept requires another to be present
all	Positive hypercube (required dimensions)
notAll	Negative hypercube (prohibited dimensions)
hypercube-dimension	Links hypercube to its dimensions
dimension-domain	Links dimension to its domain
domain-member	Links domain to its members

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5. Reference Linkbase

Purpose: Links concepts to authoritative literature (standards, regulations).

• Stores pointers like: Standard name, Section, Paragraph, Sub-paragraph
• Does NOT store the regulation text itself

Example: A concept for "Revenue" might reference "IFRS 15, paragraph 46".

How Linkbases Connect to Schemas

05 XBRL Schemas reference linkbases via <link:linkbaseRef> elements. Each reference includes:

• xlink:href -- Path to the linkbase file
• xlink:role -- Which type of linkbase (label, presentation, calculation, definition, reference)
• xlink:arcrole -- Always http://www.w3.org/1999/xlink/properties/linkbase

Linkbase Naming Conventions

Many taxonomies follow naming patterns:

Prefix	Linkbase Type
lab_	Label
pre_	Presentation
cal_	Calculation
def_	Definition
ref_	Reference
gla_	Generic label (alternative labels)
doc_	Documentation labels

See 20 CIPC Taxonomy Example for how the CIPC taxonomy uses all five linkbase types extensively.