Copyright ©2008 XBRL International Inc., All Rights Reserved.
Circulation of this Candidate Recommendation is unrestricted. This document is normative. Other documents may supersede this document. Recipients are invited to submit comments to formula-feedback@xbrl.org, and to submit notification of any relevant patent rights of which they are aware and to provide supporting documentation.
This document describes an extension to the XBRL 2.1 specification [XBRL 2.1] that builds upon the XBRL formula specification [FORMULA] and XBRL variable specification [VARIABLES] to provide the base syntax for expression of assertions that may be tested against the content of XBRL reports. This specification does not define any specific assertion, but provides a set of common definitions, resources and relationships that serve as a common foundation for XBRL assertion specifications.
1 Introduction
1.1 Background
1.2 Relationship to other work
1.3 Language independence
1.4 Terminology
1.5 Document conventions (non-normative)
1.6 Namespaces and namespace prefixes
1.7 XPath usage
2 Syntax
2.1 Assertions
2.2 Assertion relationships
2.3 Assertion sets
2.3.1 Assertion-set relationships
3 The processing model for all assertions
A Normative schema
B References
C Intellectual property status (non-normative)
D Acknowledgements (non-normative)
E Document history (non-normative)
F Errata corrections in this document
1 Namespaces and namespace prefixes
1 Typical existence assertions
2 Typical value assertions
3 Typical consistency assertions
assertion
assertion data set
assertion evaluation
assertion evaluation is not satisfied
assertion evaluation is satisfied
assertion input
assertion set
assertion test
assertion-set relationship
rfc2119 terminology
An important feature of XBRL is its ability to declare not only business concepts definitions, but also rules that constrain the information in business reports. For instance:
Such constraints can improve the quality of data in business reporting environments. However, the validations that can be expressed using the XBRL Specification [XBRL 2.1] and XBRL Dimensions Specification [DIMENSIONS] do not address the kinds of complex business rules that are common in regulatory contexts such as prudential reporting.
This document specifies the base XML syntax [XML] for such business rules. Each business rule takes the form of an assertion about one or more properties of an XBRL instance. Validation of an XBRL instance against a set of business rules involves testing that instance against a set of assertions about it. Some assertions are simple statements that an instance should or should not contain facts with a specified set of properties. For example:
A second category of assertions can be expressed as restrictions on the allowed values of facts in an XBRL instance.
Other types of assertions can be expressed as mathematical relationships that are expected to hold in XBRL instances. Such assertions involve a functional relationship mapping a set of inputs to an expected output. For example:
Validation of an XBRL instance involves: choosing an assertion set, optionally specifying values for some parameters, and then testing the assertions in the assertion set against the data in the XBRL instance.
An XBRL instance can contain more than one data set for which a given assertion can be tested. The "balance sheet must balance" assertion, for example, could be tested against balance sheets reported for multiple financial years and for multiple reporting entities, all within the one XBRL instance.
When tested against a data set in an XBRL instance, an assertion returns true if the assertion is found to hold and false otherwise.
This specification defines syntax for expressing assertions and their relationships to other data structures in XLink extended links [XLINK]. The syntax for specific assertions is expressed in separate specifications that leverage both the XBRL Variables Specification [VARIABLES] and the XBRL Formulae Specification [FORMULA]. Assertions are documented using generic labels [GENERIC LABELS] and generic references [GENERIC REFERENCES].
Many of the syntax constraints imposed by this specification are enforced by the normative schema Appendix A. To eliminate the potential for conflicts, this specification only enunciates requirements that are not enforced by the normative schema.
This specification is intended to be augmented by separate assertion specifications that define the syntax for different kinds of assertions that can be tested against data in XBRL instances.
This specification builds on the foundation provided by the XBRL Formula Specification [FORMULA] and the XBRL Variables Specification [VARIABLES].
The official language of XBRL International's own work products is English and the preferred spelling convention is UK English.
This specification is consistent with the definitions of any of the terms defined in specifications that it depends on.
The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, in this specification, are to be interpreted as described in [IETF RFC 2119].
Documentation conventions follow those set out in the XBRL Variables Specification [VARIABLES].
Namespace prefixes [XML NAMES]
will be used
for elements and attributes in
the form ns:name where ns is the
namespace prefix and name is the local name.
Throughout this specification, the mappings
from namespace prefixes to actual namespaces is consistent
with
Table 1.
The prefix column in Table 1 is non normative. The namespace URI column is normative.
| Prefix | Namespace URI |
|---|---|
validation
|
http://xbrl.org/2008/validation
|
xbrlvalide
|
http://xbrl.org/2008/validation/error
|
eg
|
http://example.com/
|
fn
|
http://www.w3.org/2005/xpath-functions
|
link
|
http://www.xbrl.org/2003/linkbase
|
xbrli
|
http://www.xbrl.org/2003/instance
|
xfi
|
http://www.xbrl.org/2005/function/instance
|
xbrldi
|
http://xbrl.org/2006/xbrldi
|
xbrldt
|
http://xbrl.org/2005/xbrldt
|
xl
|
http://www.xbrl.org/2003/XLink
|
xlink
|
http://www.w3.org/1999/xlink
|
xs
|
http://www.w3.org/2001/XMLSchema
|
xsi
|
http://www.w3.org/2001/XMLSchema-instance
|
gen
|
http://xbrl.org/2008/generic
|
variable
|
http://xbrl.org/2008/variable
|
iso4217
|
http://www.xbrl.org/2003/iso4217
|
This specification only provides a textual declaration of syntax constraints when those constraints are not expressed by the normative schema supplied with this specification.
Explanations of elements and attributes are only supplied when explanations are not already provided in other specifications.
Unless explicitly stated otherwise, a reference to a specific element MUST be read as a reference to that element or to any element in its substitution group.
Assertions are expressed by XLink resources in XLink extended links.
All assertions MUST be in the
substitution group
for the
<validation:assertion> element
or the
<validation:variableSetAssertion> element.
Because assertions that are in the
substitution group
for the
<validation:variableSetAssertion>
element, they are also in the substitution group for the <variable:variableSet> element.
As a consequence, such assertions can be starting resources for those relationships that are required
to have a
variable-set as starting resource.
The following relationships are subject to this requirement:
Assertion specifications MAY define new relationships with other resources.
An assertion set is an resource expressed by the
<validation:assertionSet> element.
Assertion sets serve to define groupings of assertions.
If an assertion is part of the set of assertions defined by an assertion set then it MUST have an assertion-set relationship to the assertion set.
An assertion-set relationship is a relationship between an assertion-set and an assertion that is expressed by an XLink arc.
To declare an assertion-set relationship an XLink arc MUST:
http://xbrl.org/arcrole/2008/assertion-set
The arcrole value,
http://xbrl.org/arcrole/2008/assertion-set,
is declared in the normative schema supplied with this spcification.
Assertion-set relationships MUST be expressed by generic arcs as indicated by the restrictions imposed by the arcrole declaration in the normative schema. Violations of this requirement will be detected by validation against the XBRL Specification [XBRL 2.1].
This section defines key features of the processing model for all assertions. Assertion specifications may augment these key features of the processing model.
All assertions are tested against an assertion input.
An assertion input, is a target XBRL instance and the values of the parameters supplied with that target XBRL instance.
An assertion data set is a subset of information in or derived from the assertion input that can be tested against an assertion.
An assertion evaluation is the result produced by testing an assertion against an assertion data set
An assertion input can contain more than one assertion data set for a given assertion. Given an assertion input, an assertion MAY be evaluated once for each assertion data set in the assertion input.
An assertion test is the effective Boolean value produced by an assertion evaluation.
An assertion evaluation is satisfied
when its assertion test equals true.
An assertion evaluation is not satisfied
when its assertion test equals false.
Assertion specifications MUST define the assertion data sets for the assertions being specified.
Assertion specifications MUST also specify how the assertions being defined are to be evaluated using the assertion data sets to produce assertion tests.
The following is the XML schema provided as part of this specification. This is normative. Non-normative versions (which should be identical to these except for appropriate comments indicating their non-normative status) are also provided as separate files for convenience of users of the specification.
NOTE: (non-normative) Following the schema maintenance policy of XBRL International, it is the intent (but is not guaranteed) that the location of non-normative versions of these schemas on the web will be as follows:
http://www.xbrl.org/2008/ - during the drafting process for
this specification this directory should contain a copy of the
most recent published version of the schema at
http://www.xbrl.org/2008/validation.xsd.
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to XBRL International or XBRL organizations, except as required to translate it into languages other than English. Members of XBRL International agree to grant certain licenses under the XBRL International Intellectual Property Policy (www.xbrl.org/legal).
This document and the information contained herein is provided on an "AS IS" basis and XBRL INTERNATIONAL DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
The attention of users of this document is directed to the possibility that compliance with or adoption of XBRL International specifications may require use of an invention covered by patent rights. XBRL International shall not be responsible for identifying patents for which a license may be required by any XBRL International specification, or for conducting legal inquiries into the legal validity or scope of those patents that are brought to its attention. XBRL International specifications are prospective and advisory only. Prospective users are responsible for protecting themselves against liability for infringement of patents. XBRL International takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Members of XBRL International agree to grant certain licenses under the XBRL International Intellectual Property Policy (www.xbrl.org/legal).
This document could not have been written without the contributions of many people including the participants in the Formula Working Group.
| Date | Author | Details |
|---|---|---|
| 30 June 2007 | Geoff Shuetrim |
Initial draft created. |
| 22 July 2007 | Geoff Shuetrim |
Converted to XML format. |
| 15 October 2007 | Geoff Shuetrim |
Adapted to XBRLspec syntax. |
| 18 November 2007 | Victor Morilla |
Created initial draft of validation specification from contents of validation-report specification by Geoff Shuetrim. |
| 18 November 2007 | Victor Morilla |
Removed references to variable set resources. Included proposal of relationships for preconditions and group filters |
| 26 November 2007 | Geoff Shuetrim |
Fixed up typographic errors. Added comments and responses to questions. Added a formal definition of an assertion set. |
| 26 November 2007 | Geoff Shuetrim |
Fixed up typographic errors. Added comments and responses to questions. Added a formal definition of an assertion set. |
| 30 November 2007 | Victor Morilla |
Adapted to new variable specification. Included Geoff's comments. |
| 04 December 2007 | Victor Morilla |
Included hint about usage of assertion-sets. Removed obsolete comments Moved assertion-formula relationship to consistency-assertion spec |
| 06 December 2007 | Victor Morilla |
Recovered the definition of the assertion data set Removed obsolete comments |
| 09 December 2007 | Victor Morilla |
Removed the validationArc in favour of generic arcs. assertion-set relationships now used on generic arcs. |
| 10 December 2007 | Victor Morilla |
Included two abstract elements for assertions; one in the substitution group for variable:resource and another one in the substitution group for variable:variableSet. Those assertions that determine a variable-set (value and existence) must be in the substitution group for the latter; others (consistency assertions) must be in the substitution group for the former. |
| 31 January 2008 | Geoff Shuetrim |
Standardised the format of the hyperlinks to the normative schema. Standardised the boilerplate text for errata. |
| 03 February 2008 | Geoff Shuetrim |
Revised the abstract to simplify the wording and to provide links to the underpinning specifications. |
| 04 February 2008 | Geoff Shuetrim |
Corrected a range of minor grammatical problems in the text of the the specification and clarified a number of definitions. Moved the paragraphs on data sets from the syntax section to the processing model section. |
| 04 February 2008 | Geoff Shuetrim |
Made small clarifications to the wording of the processing model documentation. |
This appendix contains a list of the errata that have been incorporated into this document. This represents all those errata corrections that have been approved by the XBRL International Formula Working Group up to and including 28 March 2008. Hyperlinks to relevant e-mail threads may only be followed by those who have access to the relevant mailing lists. Access to internal XBRL mailing lists is restricted to members of XBRL International Inc.
No errata have been incorporated into this document.