1 Introduction

This specification is an extension to [VARIABLES]. It defines XML syntax [XML] for filters that can condition on criteria relating to fact values when selecting facts from XBRL instances.

Note that fact selection based upon the actual value of the fact is straightforwardly done using general filters. The filters in this specification provide filtering capabilities relating to facts with nil values and relating to the precision of numeric facts.

In relation to implicit filtering, as defined in the XBRL Variables Specification [VARIABLES], none of the filters defined in this specification cover any aspects of facts.

1.1 Background

This specification is a member of a suite of similar specifications that define specific types of criteria that can be used to select facts from XBRL instances. It enhances the fact selection capabilities of the XBRL Variables Specification [VARIABLES].

1.2 Relationship to other work

This specification depends upon the XBRL Specification [XBRL 2.1], and the XBRL Variables Specification [VARIABLES]. In the event of any conflicts between this specification and the specifications upon which it depends, this specification does not prevail.

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.

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
`vf`	`http://xbrl.org/2008/filter/value`
`xbrlvfe`	`http://xbrl.org/2008/filter/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/2008/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`

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 Nil filter

A nil filter is declared by an <vf:nil> element.

The syntax for the <vf:nil> element is defined by the normative schema supplied with this specification.

The nil filter can be used to match facts that are reported as nil.

The XPath expression implied by a nil filter is:

fn:nilled(.)

2.2 Precision filter

A precision filter is declared by an <vf:precision> element.

The syntax for the <vf:precision> element is defined by the normative schema supplied with this specification.

The precision filter can be used to match facts based on their having a minimum actual or inferred precision, noting that precision can be inferred from the value of the @decimal attribute.

The XPath expression implied by a precision filter is:

if (fn:string(#minimum) eq 'INF') then fn:false() else if (fn:nilled(.)) then fn:false() else if (xfi:is-non-numeric(.))) then fn:false() else if (xfi:is-fraction(.)) then fn:true() else if (fn:string(xfi:precision(.)) eq 'INF') then fn:true() else (xfi:precision(.) ge xs:nonNegativeInteger(#minimum+0.0))

where #minimum is the value of the @minimum attribute on the precision filter.

Note that the precision filter will not select facts if the filter implies an infinite minimum required precision. The filter will also not select non-numeric facts or facts that are reported with a nil value.

If a fact is not rejected by a precision filter for the above reasons, then the precision filter will select those facts with a data type that is xbrli:fractionItemType or that is derived from the xbrli:fractionItemType data type. It will also select those facts with other numeric data types if their inferred precision is greater or equal to the specified minimum.

Example 1: Precision filters

#minimum	Implied constraint
`1`	The fact must be numeric and the inferred precision must be greater than or equal to one.
`4`	The fact must be numeric and the inferred precision must be greater than or equal to four.

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-filter.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

VARIABLES: XBRL International Inc.. "XBRL Variables 1.0"
Phillip Engel, Herm Fischer, Victor Morilla, Jim Richards, Geoff Shuetrim, David vun Kannon, and Hugh Wallis.
(See ../../variables/REC-2009-06-22/variables-REC-2009-06-22.html)
XBRL 2.1: XBRL International Inc.. "Extensible Business Reporting Language (XBRL) 2.1"
Phillip Engel, Walter Hamscher, Geoff Shuetrim, David vun Kannon, and Hugh Wallis.
(See http://www.xbrl.org/Specification/XBRL-RECOMMENDATION-2003-12-31+Corrected-Errata-2008-07-02.htm)
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/)

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
29 May 2007	Geoff Shuetrim	First internal working draft created.
11 June 2007	Geoff Shuetrim	Fixed up the value filter implied XPath expression to make it consistent with the syntax of other implied XPath expressions and to eliminate the call to some xfi:value function. Changed spelling of nill to nil.
24 July 2007	Hugh Wallis	Edited for public working draft publication.
05 November 2007	Geoff Shuetrim	Converted the specification to XML format. Added in the definitions and the hyperlinks to the relevant sections of the normative schema. Added comments about simplifications that should be made. Eliminated the not nil filter because it will be redundant when we have the ability to use the not() operator with filters. Added the example for the value filter. Added the example for the precision filter. Added extra explanations in relation to the treatment of non-numeric facts for the precision filter.
02 December 2007	Geoff Shuetrim	Changed the example comparison operators to value comparison operators on the advice of Herm Fischer.
31 January 2008	Geoff Shuetrim	Standardised the format of the hyperlinks to the normative schema. Removed the erroneous statement that the filters defined in this specification can cover the entity aspect of facts, as suggested by Masatomo Goto. Added a test for nil facts to the precision filter as suggested by Masatomo Goto. Changed the comparison operator to a value comparison operator in the implied XPath expression for the precision filter. Ensured that precision filters throw an error if the minimum allowed precision value is not a finite number.
01 February 2008	Geoff Shuetrim	Corrected errors in the value filter examples and the precision filter examples.
05 February 2008	Geoff Shuetrim	Used the standard XPath 2.0 function to test if facts are nil rather than an XBRL function.
08 February 2008	Geoff Shuetrim	Revised the implied XPath expression for the precision filter in line with feedback on its effectiveness from Masatomo Goto. The filter now handles items with data types derived from the `xbrli:fractionItemType` and it handles nil facts and it handles cases where the specified minimum is infinite. As agreed by the working group, removed the value filter from the specification because it is equivalent to the general filter. The example for the value filter was moved to the general filter specification.
07 March 2008	Geoff Shuetrim	Changed the precision filter example to not use an invalid minimum precision of zero as suggested by Takahide Muramoto.
13 March 2008	Geoff Shuetrim	Fixed the function for xfi:is-fraction and added the brackets for fn:false in the implied XPath expression for the precision filter as suggested by Takahide Muramoto. Made the text of the specification consistent with the `ge` operator in the implied XPath expression of the precision filter as suggested by Takahide Muramoto.
20 March 2008	Geoff Shuetrim	Fixed broken hyperlinks.
14 April 2008	Geoff Shuetrim	`xfi:non-numeric` changed to `xfi:is-non-numeric` to conform with the function registry as suggested by Takahide Muramoto.

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 22 June 2009. 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 Filters 1.0

Recommendation 22 June 2009

Status

Abstract

Table of Contents

Appendices

Table

Example

Definitions