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 provide supporting documentation.
This specification is an extension to the XBRL Variables Specification [VARIABLES]. This specification defines an approach for associating filters with fact variables.
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 Implicit filters
2.1 Non-dimensional implicit filters
2.2 Dimensional implicit filters
A References
B Intellectual property status (non-normative)
C Acknowledgements (non-normative)
D Document history (non-normative)
E Errata corrections in this document
1 Namespaces and namespace prefixes
2 Aspects defined for non-dimensional implicit filtering
3 Aspects defined for dimensional implicit filtering
1 Determination of the match filter to be inferred
2
Implicit filtering with a non-dimensional aspect model to support equity calculation formulae.
3
Implicit filtering with a dimensional aspect model to support calculation of end-of-period stocks.
aspect universe
current-variable
dimensional implicit filters
implicit filters
implicit value of an aspect
matchable aspect
non-dimensional implicit filters
preceding variable
This specification is an extension to the XBRL Variables 1.0 Specification [VARIABLES]. It defines implicit filtering schemes for inferring associations between fact variables and filters.
Implicit associations between fact variables and filters are complementary to the variable-filter relationships defined in the XBRL Variables Specification [VARIABLES]. The implicit associations are determined by analysis of uncovered aspects, considering only those filters that are associated with variables by variable-filter relationships.
Implicit filters are intended to reduce the verbosity of fact variables by inferring match filters [MATCH FILTERS] for the uncovered aspects of fact variables in a variable set.
These inferred match filters serve to equate the values of uncovered aspects across fact variables. For any two fact variables in a variable set that do not have filters covering a specific aspect, those two fact variables will only ever evaluate to facts that report equivalent values for that aspect.
For any aspect that is uncovered for at least one fact variable in a variable set, The implicit value of that aspect is the the value that it takes for each fact variable in the variable set that does not have a filter covering that aspect.
It is possible for the implicit value of an aspect to be a missing value for that aspect. In other words, it is possible for an aspect not to be reported for all of the facts that all of the fact variables, not covering the aspect, have evaluated to.
Implicit filters are only associated with fact variables in variable sets that indicate that they are to be evaluated with implicit filtering.
This specification defines two different forms of implicit filtering, one that does not take the XBRL Dimensions Specification [DIMENSIONS] into account and one that does.
Which form of implicit filtering, if any, is used when evaluating a variable set depends on the aspect model of the variable set.
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 simplifies the declaration of the filters needed to match the aspects of facts across fact variables that are evaluated as a group.
This specification depends upon the XBRL Specification [XBRL 2.1], 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.
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.
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 |
|---|---|
xbrlife
|
http://xbrl.org/2008/filter/implicit/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
|
generic
|
http://xbrl.org/2008/generic
|
variable
|
http://xbrl.org/2008/variable
|
iso4217
|
http://www.xbrl.org/2003/iso4217
|
An implicit filter is a filter that has been inferred to be associated with a fact variable in a variable set rather than explicitly associated with the fact variable by an XLink arc.
Implicit filters do not cover any aspect.
When evaluating variable sets using implicit filtering, the implicit filters to infer are determined during the evaluation process. The current variable is the fact variable that is currently being evaluated. Implicit filters are inferred for the current variable according to the rules set out in this section.
A preceding variable for the current variable is a fact variable in the same variable set as the current variable that has already been evaluated to a sequence of one or more facts.
The aspect universe is the set of all aspects for which values are reported (explicitly or by default) in the target XBRL instance.
A matchable aspect is an aspect in the aspect universe that is not covered for the current variable and that is not covered for at least one of the current variable's preceding variables.
A match filter is inferred for each of its matchable aspects of the current variable.
The match filter that is inferred for each matchable aspect, must be the match filter that selects for facts by matching the value of the matchable aspect.
The implicit filter for an uncovered concept aspect would be a concept matching filter.
Similarly, the implicit filter for an uncovered period aspect would be a period matching filter.
The matched variable for each inferred match filter is any one of the preceding variables that did not have a filter that covered the aspect being matched by the inferred match filter.
This specification defines two different variations of implicit filters, one to handle implicit filtering when processing formulae and instances that are based on the XBRL Dimensions Specification [DIMENSIONS] (see Section 2.1), and one that is appropriate when processing formulae and instances that are only based on the XBRL Specification [XBRL 2.1] (see Section 2.2).
The only distinction between non-dimensional implicit filters and dimensional implicit filters is in terms of the aspects that they identify from the existence and content of segments and scenarios.
Non-dimensional implicit filters are implicit filters that do not take the XBRL Dimensions Specification [DIMENSIONS] into account when determining the filters to be applied to the content of segments and scenarios.
Non-dimensional implicit filters are used for variable sets requiring implicit filtering and using the non-dimensional aspect model.
The following table sets out the aspects that are defined with regard to dimensional implicit filtering and the match filters that are used for those aspects:
Example 2 shows the small number of non-implicit filters required to define variables that would support computation of equity from data on assets and liabilities. Only the covering concept-name filters need to be explicit. All others are implicit.
| Variables in the variable set | |
|---|---|
| Variable | Filters |
eg:assets
|
|
eg:liabilities
|
|
dimensional implicit filters are implicit filters that do take the XBRL Dimensions Specification [DIMENSIONS] into account when determining the filters to be applied to the content of segments and scenarios.
Dimensional implicit filters are used for variable sets requiring implicit filtering and using the dimensional aspect model.
The following table sets out the aspects that are defined with regard to dimensional implicit filtering and the match filters that are used for those aspects:
Example 3 shows the small number of non-implicit filters required to define variables that would support stock flow computations. Only the covering concept-name, instant-duration and typed dimension filters are explicit. All others are implicit.
| Variables in the variable set | |
|---|---|
| Variable | Filters |
eg:flow
|
|
eg:startingStock
|
|
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This document could not have been written without the contributions of many people including the participants in the Formula Working Group.
| Date | Author | Details |
|---|---|---|
| 15 November 2007 | Geoff Shuetrim |
First internal working draft started, drawing upon the ideas put forward by Victor Morilla and Paul Bull. |
| 19 November 2007 | Geoff Shuetrim |
Completed the first draft of the implicit filter specification. |
| 25 November 2007 | Victor Morilla |
Included comments and proposed changes about the matched variable |
| 29 November 2007 | Geoff Shuetrim |
Fixed up the rules for inferring matching filters to ensure that we cover tricky situations involving facts reported with differing sets of aspects (such as could occur if we have concepts in the DTS that are associated with more than one conjunction of hypercubes). |
| 01 December 2007 | Geoff Shuetrim |
Added examples. |
| 13 March 2008 | Geoff Shuetrim |
Made the introduction more easily read by breaking up the larger paragraphs. Added explanatory paragraph for each of the examples. These changes were suggested by CompSci Resources. |
| 20 March 2008 | Geoff Shuetrim |
Fixed broken hyperlinks. |
| 27 August 2008 | Geoff Shuetrim |
Collapsed the segment dimension and scenario dimension aspects into the one dimension aspect in line with changes to the dimensional aspect model. |
| 15 December 2008 | Geoff Shuetrim |
Updated references to the latest errata-corrected version of the XBRL 2.1 specification. |
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 31 December 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.