1 Introduction

This specification is an extension to the XBRL Validation specification [VALIDATION]. It defines XML syntax [XML] for assertions that test the values of the variables of each evaluation of a given variable set. It is a construct similar to that of a formula resource, but its output is a boolean value instead of a complete XBRL fact. The Boolean value is obtained by evaluating the an XPath expression that is specified as part of the assertion.

This kind of assertion supports the expression of business rules that can be used to perform checks like those set out in Example 1.

Example 1: Value assertions

Assets must be equal to liabilities plus equities.
The total amount of incomes for a company must be equal or less than the addition of the total incomes of its subsidiaries.
The figures of the balance sheet of a company must be equal to the addition of its breakdown by market segment.
The difference of current assets of the current period and the previous one must be lower than a certain threshold.
The difference between a starting balance and an ending balance must be equal to the flows during the intervening period.

Many of the syntax constraints imposed by this specification are set out in the normative schema Appendix A. To eliminate the potential for conflicts, this specification only describes syntax features that are not expressed in the normative schema.

1.1 Background

This specification is a member of a suite of similar specifications that define specific types of assertions tested against the information contained in XBRL business reports.

1.2 Relationship to other work

This specification builds on the foundation provided by the XBRL Variable specification [VARIABLES].

Although this specification does not depend on the XBRL Formula Specification [], it uses a similar processing model and shares many features with that specification.

1.3 Language independence

The official language of XBRL International's own work products is English and the preferred spelling convention is UK English.

1.4 Terminology

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].

1.5 Document conventions (non-normative)

Documentation conventions follow those set out in the XBRL Variables Specification [VARIABLES].

1.6 Namespaces and namespace prefixes

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.

Table 1: Namespaces and namespace prefixes

Prefix	Namespace URI
`va`	`http://xbrl.org/2008/assertion/value`
`xbrlvae`	`http://xbrl.org/2008/assertion/value/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`
`validation`	`http://xbrl.org/2008/validation`

1.7 XPath usage

XPath usage is identical to that in the XBRL Variables Specification [VARIABLES].

2 Syntax

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.

2.1 Value Assertions

A value assertion is a statement about a value that is provided in or can be derived from an assertion input.

Value assertions are expressed by the <va:valueAssertion> element in the normative schema supplied with this specification.

A value assertion expression is the XPath expression contained by the @test attribute on a value assertion.

3 The processing model for value assertions

The assertion data set for a value assertion is an evaluation of the variable set defined by the value assertion.

Each different evaluation of a value assertion's variable set constitutes a different data set for the variable assertion.

Value assertion expressions MAY have dependencies on any of the variables and parameters in the variable sets defined by their value assertions. For this reason, value assertions can only be evaluated if the variable set that constitutes their data set has also been evaluated.

Value assertion expressions are evaluated using the <xbrli:xbrl> element of the target XBRL instance as the context item. The variables and parameters in the data set are in scope for the evaluation of the value assertion expression.

A value assertion test is the effective Boolean value produced by evaluating the value assertion expression given a suitable data set.

Appendix A Normative schema

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:

While any schema is the most current RECOMMENDED version and until it is superseded by any additional errata corrections a non-normative version will reside on the web in the directory 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/value-assertion.xsd.
A non-normative version of each schema as corrected by any update to the RECOMMENDATION will be archived in perpetuity on the web in a directory that will contain a unique identification indicating the date of the update.

</extension>

</complexContent>

</complexType>

</element>

</schema>

Appendix B References

IETF RFC 2119: IETF (Internet Engineering Task Force). "RFC 2119: Key words for use in RFCs to Indicate Requirement Levels"
Scott Bradner.
(See http://www.ietf.org/rfc/rfc2119.txt)
VALIDATION: XBRL International Inc.. "XBRL Validations 1.0, Public Working Draft"
Victor Morilla, and Geoff Shuetrim.
(See ../../validation/CR-2008-03-28/validation-CR-2008-03-28.html)
VARIABLES: XBRL International Inc.. "XBRL Variables 1.0, Public Working Draft"
Phillip Engel, Herm Fischer, Victor Morilla, Jim Richards, Geoff Shuetrim, David vun Kannon, and Hugh Wallis.
(See ../../variables/CR-2008-03-28/variables-CR-2008-03-28.html)
XML: W3C (World Wide Web Consortium). "Extensible Markup Language (XML) 1.0 (Fourth Edition)"
Tim Bray, Jean Paoli, C. M. Sperberg-McQueen, Eve Maler, and François Yergeau.
(See http://www.w3.org/TR/REC-xml/)
XML NAMES: W3C (World Wide Web Consortium). "Namespaces in XML 1.0 (Second Edition)"
Tim Bray, Dave Hollander, Andrew Layman, and Richard Tobin.
(See http://www.w3.org/TR/REC-xml-names/)
XML SCHEMA STRUCTURES: W3C (World Wide Web Consortium). "XML Schema Part 1: Structures Second Edition"
Henry S. Thompson, David Beech, Murray Maloney, and Noah Mendelsohn.
(See http://www.w3.org/TR/xmlschema-1/)
XPATH 2.0: W3C (World Wide Web Consortium). "XML Path Language (XPath) 2.0"
Anders Berglund, Scott Boag, Don Chamberlin, Mary F. Fernández, Michael Kay, Jonathan Robie, and Jérôme Siméon.
(See http://www.w3.org/TR/xpath20/)

Appendix C Intellectual property status (non-normative)

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).

Appendix D Acknowledgements (non-normative)

This document could not have been written without the contributions of many people including the participants in the Formula Working Group.

Appendix E Document history (non-normative)

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.
15 October 2007	Geoff Shuetrim	Adapted to XBRLspec syntax.
20 November 2007	Victor Morilla	Created fact value assertions from validation report spec
24 November 2007	Victor Morilla	Removed references to variable set resources
06 December 2007	Victor Morilla	References to the definition of the assertion data set
16 December 2007	Victor Morilla	Changed namespace of value assertions from http://xbrl.org/2008/value-assertion to http://xbrl.org/2008/assertion/value
29 January 2008	Victor Morilla	Removed constraint on the number of fact variables of value assertions and its corresponding error as suggested by Herm Fischer. This way, this document is consistent with the formula specification and assertions not dependent on fact variables can be expressed.
31 January 2008	Geoff Shuetrim	Standardised the format of the hyperlinks to the normative schema. Standardised the boilerplate text for errata.
05 February 2008	Geoff Shuetrim	Aligned the element name for the value assertion resource to the element name in the normative schema.
06 February 2008	Geoff Shuetrim	Clarified the definition of the data set for a value assertion. Eliminated the redundant section on relationships that are allowed to value assertions. Combined the section on the test defined by a value assertion with the section on the processing model for value assertions. Eliminated redundant parts of the processing model documentation. Eliminated the reference to an XML attribute in the abstract because the abstract should be completely non-technical.
20 March 2008	Geoff Shuetrim	Fixed broken hyperlinks.

Appendix F Errata corrections in this document

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.

Value Assertions 1.0

Candidate Recommendation 28 March 2008

Status

Abstract

Table of Contents

Appendices

Table

Example

Definitions