XBRL Period Filters Specification 1.0
Internal Working Draft, dated 2007-07-13
Copyright © 2006-7, XBRL International Inc., All Rights Reserved
This version:
Period-Filters-PWD-2007-07-13.rtf
is NORMATIVE. All other versions and formats are non-normative.
Editors
Name	Contact	Affiliation	
Phillip Engel	phillip.engel@morganstanley.com 	Morgan Stanley	
Geoff Shuetrim	geoff@galexy.net	Galexy	
David vun Kannon	david.k.vunkannon@us.pwc.com 	PricewaterhouseCoopers LLP	
Hugh Wallis	hughwallis@xbrl.org	XBRL International	
Contributors
			
Abstract
This specification is an extension to the XBRL Variables 1.0 Specification [VARIABLES].  It specifies syntax for filters that can be used to ensure that a variable only binds to facts meeting specified criteria in relation to the values of their context periods.
Status
This is a Public Working Draft whose circulation is unrestricted. Comments should be directed to the editor and/or contributors by e-mail.  Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to provide supporting documentation.
In the final version of this document:
•	relevant schema extracts will be included in the text of the specification
•	relevant examples will be included
•	error codes will be included.
To reduce the editorial burden, these aspects of the specification have been omitted for internal working drafts.
Normative status
This document is normative in the sense that any implementing processor must obey the rules described within it, in order to be considered a conformant processor.

Table of contents
1.1	Document conventions (non-normative)
1.1.1	Typographic conventions
1.1.2	Formatting conventions
1.1.3	Namespace conventions (normative)
1.2	Relationship to other work
1.3	Language independence
1.4	Terminology
1.5	XPath usage
2	Introduction
3	Syntax
3.1	Matching period filter
3.2	Period filters
3.3	Period start filters
3.4	Period end filters
3.5	Instant filters
3.6	Instant-duration filters
Appendices
A	References (Non Normative)
B	Normative schema
C	Intellectual Property Status (non-normative)
D	Acknowledgements (non-normative)
E	Document History (non-normative)
F	Approval process (non-normative)

1.1	Document conventions (non-normative)
1.1.1	Typographic conventions
Comments which are informative, but not essential to the understanding of the point at hand are provided in footnotes. All footnotes are non-normative.
1.1.2	Formatting conventions
The following highlighting is used to present normative technical material in this document:
	
The following formatting is used for non-normative examples in this document:

The following formatting is used for non-normative counterexamples (examples of poor, discouraged or disallowed usage) in this document:

1.1.3	Namespace conventions (normative)
This table contains all the prefixes used within the text and the correspondent namespace URI. The prefix column in the table above is non normative. The namespace URI column is normative.
Prefix	Namespace URI	
xbrli	http://www.xbrl.org/2003/instance	
xs	http://www.w3.org/2001/XMLSchema	
xfi	http://www.xbrl.org/2005/function/instance	
fn	http://www.w3.org/2006/xpath-functions	
xlink	http://www.w3.org/1999/xlink	
link	http://www.xbrl.org/2003/linkbase	
xl	http://www.xbrl.org/2003/XLink	
generic	http://xbrl.org/2007/generic	
variable	http://xbrl.org/2007/variable	
filter	http://xbrl.org/2007/filter/period	
1.2	Relationship to other work
This specification depends upon XBRL 2.1 Specification [XBRL]. This specification depends upon XBRL Variables 1.0 Specification [VARIABLES].
In the event of any conflicts between this specification and the specifications upon which it depends, this specification does not prevail.
This specification has dependencies on specific XBRL functions [XBRLFunc] that will need to be defined.
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
All terminology defined in the XBRL 2.1 Specification is used unchanged in this specification.
The following additional terms are used as described in the table below:
Term	Meaning (Normative)	
period filter	A filter that can condition on the information in a context period.	

		

		
1.5	XPath usage
XPath usage is identical to that in the XBRL Formula 1.0 Specification [FORMULA].
2	Introduction
This specification provides syntax for filters that can be used to ensure that a variable only binds to facts meeting specified criteria in relation to the values of their context periods.
In relation to implicit filtering, as defined in the XBRL Variables Specification [VARIABLES], all filters defined in this specification cover the period aspect of facts.

3	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 those explanations are not already provided in other specifications.
Where the value of an attribute is to be inserted into an XPath expression to define the XPath expression implied by a filter, that value will be referred to in the XPath expression using a # sign followed by the name of the attribute.
3.1	Matching period filter
The matching period filter is declared using the filter:periodMatch element.  It supports filtrations for facts where their period matches that of another fact.  The matching period filter can be used regardless of whether the facts being compared have instant, duration or forever style periods.
The syntax for the matching period filter is defined by the normative schema supplied with this specification.
The XPath expression implied by a matching period filter is constructed as follows:
xfi:period[xfi:s-equal(.,#other)]
The value of the other attribute on a matching period filter is an XPath expression that evaluates to an xbrli:period element.
For example, if the other attribute had a value of xfi:period($otherVariable), then the filter would match facts by period against the period of the fact that the otherVariable had evaluated to.
If, instead, the other attribute had a value of xfi:create-period(), then the filter would match any facts with a forever period.
3.2	Period filters
IT can also be useful to use filters that support more flexible conditioning on period information.  The filter:period element supports such flexibility.  It is referred to as a period filter.
The syntax for the period filter is defined by the normative schema supplied with this specification.
The XPath expression implied by an period filter is given by:
xfi:period(.)[#test]
For example, given another variable with QName, my:other, the value of the test attribute might be:
xfi:period-start(.)=xfi:period-end(xfi-period($my:other))
This would ensure that all facts meeting the criteria specified by the period filter had a finite duration period with a start that matched the end of the finite duration period for the fact matched by the my:other variable.
By setting the value of the test attribute to true, the filter would select any facts with an instant period.
By setting the value of the test attribute to xfi:is-instant-period(.) the period filter would select for facts that have instant periods.
By setting the value of the test attribute to:
xfi:is-instant-period(.) and
xfi:instant(.) = xs:dateTime(xs:date('1999-12-31'),xs:time('00:00:00'))
the filter will select facts with an instant period that equals 1999-12-31T12:00:00.
3.3	Period start filters
The filter:periodStart element supports filtrations for facts based upon the value of the start of a finite duration.  It is referred to as a period start filter.
The syntax for the period start filter is defined by the normative schema supplied with this specification.
If the period start filter has a time attribute, then the implied XPath expression is obtained from:
xfi:period[
xfi:is-start-end-period(.) and
xfi:period-start(.) = xs:dateTime(#date,#time)
]
Otherwise, the XPath expression implied by a period start filter is obtained from:
xfi:period[
xfi:is-start-end-period(.) and
xfi:period-start(.) =
(xs:dateTime(#date,'00:00:00') + xs:dayTimeDuration('P1D'))
]
The date attribute MUST contain an XPath expression that evaluates to an xs:date value.  The time attribute, if supplied, MUST contain an XPath expression that evaluates to an xs:time value.
3.4	Period end filters
The filter:periodEnd element supports filtrations for facts based upon the value of the end of a finite duration.  It is referred to as a period end filter.
The syntax for the period end filter is defined by the normative schema supplied with this specification.
If the period end filter has a time attribute, then the implied XPath expression is obtained from:
xfi:period[
xfi:is-start-end-period(.) and
xfi:period-end(.) = xs:dateTime(#date,#time)
]
Otherwise, the XPath expression implied by a period start filter is obtained from:
xfi:period[
xfi:is-start-end-period(.) and
xfi:period-end(.)=
(xs:dateTime(#date,'00:00:00')+ xs:dayTimeDuration('P1D'))
]
The date attribute MUST contain an XPath expression that evaluates to an xs:date value.  The time attribute, if supplied, MUST contain an XPath expression that evaluates to an xs:time value.
3.5	Instant filters
The filter:periodInstant element supports filtrations for facts based upon the value of the end of a finite duration.  It is referred to as an instant filter.
The syntax for the instant filter is defined by the normative schema supplied with this specification.
If the instant filter has a time attribute, then the implied XPath expression is obtained from:
xfi:period[
xfi:is-instant-period(.) and
xfi:instant(.) = xs:dateTime(#date,#time)
]
Otherwise, the XPath expression implied by a period start filter is obtained from:
xfi:period[
xfi:is-instant-period(.) and
xfi:instant(.) =
(xs:dateTime(#date,'00:00:00') + xs:dayTimeDuration('P1D'))
]
The date attribute MUST contain an XPath expression that evaluates to an xs:date value.  The time attribute, if supplied, MUST contain an XPath expression that evaluates to an xs:time value.
3.6	Instant-duration filters
The filter:periodInstantDuration element is useful for filtrations that establish equality of an instant period and either the start or end of a duration period.  It is referred to as an instant-duration filter.
The syntax for the instant-duration filter is defined by the normative schema supplied with this specification.
The XPath expression implied by a period start filter is obtained from:
xfi:period[xfi:instant(.) = #durationBoundary]
The durationBoundary attribute MUST contain an XPath expression that evaluates to an xs:dateTime value.
For a stock/flow relationship, the periods of the various fact variables could be related by an instant-duration period filter.  The filter would link the instant for the start stock to the start of the first flow to be evaluated.

Appendices
A	References (non-normative)

[FORMULA]	Phillip Engel, Geoff Shuetrim, David vun Kannon, Hugh Wallis (editors)
XBRL Formula Specification 1.0 Public Working Draft
http://www.xbrl.org/SpecPWDs/	
[VARIABLES]	Phillip Engel, Geoff Shuetrim, David vun Kannon, Hugh Wallis (editors)
XBRL Variables 1.0 Specification, Public Working Draft
http://www.xbrl.org/SpecPWDs/	
[XBRL]	Phillip Engel, Walter Hamscher, Geoff Shuetrim, David vun Kannon and Hugh Wallis
Extensible Business Reporting Language 2.1 Recommendation 
http://www.xbrl.org/SpecRecommendations/	
[XBRLFunc]	Chris Simmons (editor), Cliff Binstock, Phillip Engel, Herm Fischer, David vun Kannon, Hugh Wallis and Paul Warren
XBRL Functions 1.0 Public Working Draft
http://www.xbrl.org/SpecPWDs/	
B	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:
1)	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/2007/ - 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/2007/period-filter.xsd.

<?xml version="1.0" encoding="UTF-8"?>
<!-- Copyright 2007 XBRL International. All Rights Reserved. -->
<schema 
  targetNamespace="http://xbrl.org/2007/filter/period"
  xmlns:pf="http://xbrl.org/2007/filter/period" 
  xmlns:expression="http://xbrl.org/2007/expression" 
  xmlns:link="http://www.xbrl.org/2003/linkbase" 
  xmlns:xl="http://www.xbrl.org/2003/XLink"
  elementFormDefault="qualified"
  xmlns="http://www.w3.org/2001/XMLSchema" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="
  http://www.w3.org/2001/XMLSchema http://www.w3.org/2001/XMLSchema.xsd
  http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd
  ">

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

  <import namespace="http://xbrl.org/2007/expression" 
    schemaLocation="expression.xsd"/>

  <element name="period" substitutionGroup="xl:resource">
    <complexType mixed="true">
      <complexContent mixed="true">
        <extension base="xl:resourceType">
          <attribute name="test" type="expression:expression" use="required"/>
          <anyAttribute namespace="http://www.w3.org/XML/1998/namespace" processContents="lax"/>
        </extension>
      </complexContent>
    </complexType>
  </element>

  <element name="periodMatch" substitutionGroup="xl:resource">
    <complexType mixed="true">
      <complexContent mixed="true">
        <extension base="xl:resourceType">
          <attribute name="other" type="expression:expression" use="required"/>
          <anyAttribute namespace="http://www.w3.org/XML/1998/namespace" processContents="lax"/>
        </extension>
      </complexContent>
    </complexType>
  </element>

  <element name="periodStart" substitutionGroup="xl:resource">
    <complexType mixed="true">
      <complexContent mixed="true">
        <extension base="xl:resourceType">
          <attribute name="date" type="expression:expression" use="required"/>
          <attribute name="time" type="expression:expression" use="optional"/>
          <anyAttribute namespace="http://www.w3.org/XML/1998/namespace" processContents="lax"/>
        </extension>
      </complexContent>
    </complexType>
  </element>

  <element name="periodEnd" substitutionGroup="xl:resource">
    <complexType mixed="true">
      <complexContent mixed="true">
        <extension base="xl:resourceType">
          <attribute name="date" type="expression:expression" use="required"/>
          <attribute name="time" type="expression:expression" use="optional"/>
          <anyAttribute namespace="http://www.w3.org/XML/1998/namespace" 
          processContents="lax"/>
        </extension>
      </complexContent>
    </complexType>
  </element>

  <element name="periodInstant" substitutionGroup="xl:resource">
    <complexType mixed="true">
      <complexContent mixed="true">
        <extension base="xl:resourceType">
          <attribute name="date" type="expression:expression" use="required"/>
          <attribute name="time" type="expression:expression" use="optional"/>
          <anyAttribute namespace="http://www.w3.org/XML/1998/namespace" 
          processContents="lax"/>
        </extension>
      </complexContent>
    </complexType>
  </element>  

  <element name="periodInstantDuration" substitutionGroup="xl:resource">
    <complexType mixed="true">
      <complexContent mixed="true">
        <extension base="xl:resourceType">
          <attribute name="durationBoundary" type="expression:expression" use="required"/>
          <anyAttribute namespace="http://www.w3.org/XML/1998/namespace" 
          processContents="lax"/>
        </extension>
      </complexContent>
    </complexType>
  </element>  

</schema>	
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).
D	Acknowledgements (non-normative)
This document could not have been written without the contributions of many people including the participants in the XBRL Formula Working Group.
E	Document History (non-normative)
Date	Editor	Summary	
2006-12-18	Geoff Shuetrim	First internal working draft created, drawing extensively on the previous Formula specification drafts.	
2007-04-25	Geoff Shuetrim	Changed the target namespace of the normative schema.	
2007-04-30	Geoff Shuetrim	Significant redesign of the period filters, broadening the usefulness of the period filter and enhancing the flexibility of the specific period filters. Added a matching period filter that is specifically intended to match one period to another.  Added an instant-duration filter specifically designed to simplify the declaration of period relationships between instant and duration concepts.
In relation to implicit filtering, added indication that all of the filters defined in this specification cover the period aspect.	
2007-05-08	Geoff Shuetrim	Added clarification about the fact aspect covered by the filters defined in this specification.	
2007-05-29	Geoff Shuetrim	Changed the target namespace of the normative schema again.  Fixed incorrect reference to an instant filter in the description of the period filter.	
2007-06-11	Geoff Shuetrim	Fixed the XML Schema to make the time attributes optional, reflecting the wording of the specification.  Clarified the example that goes with the instant-duration period filter.	
2007-07-24	Hugh Wallis	Editorial for Publication	
			
F	Approval process (non-normative)
This section will be removed from the final recommendation.
This specification is being developed following the XBRL Technical Working Group Processes: http://www.xbrl.org/XSB/XBRL_Technical_Working_Group_Processes-Approved-2007-04-17.htm