Formula Specification Public Working Draft Overview
Public Working Draft dated 2007-07-13
This document:
	XBRL-Formulas-Overview-PWD-2007-07-13.rtf
is non-normative.
Editors
Geoff Shuetrim	geoff@galexy.net	Galexy Pty. Limited	
Abstract
This document explains the various materials issued as a part of the public working draft released by the Formula Working Group (FWG).
Status
Circulation of this Public Working Draft is unrestricted.  Recipients of this draft are invited to submit comments to Geoff Shuetrim, and to submit notification of any relevant patent rights of which they are aware and to provide supporting documentation.
Table of Contents
Formula Specification Public Working Draft Overview
Public Working Draft dated 2007-07-13
1	Introduction
2	Requirements
3	Specifications
4	Schemas
5	Examples
6	Conformance suite tests
7	Focus issues
7.1	Custom function signatures
7.2	Implicit filtering
7.3	Implied XPath expressions
7.4	Explicit filters
7.5	Normative schemas
A.	References (non-normative)
B.	Intellectual Property Status (non-normative)
C.	Document History (non-normative)
D.	Approval process (non‑normative)

1	Introduction
This document provides an overview of this Public Working Draft (PWD).  It describes the various materials included in the PWD by the Formula Working Group (FWG).  It also lists a series of issues about which the FWG hope to receive specific feedback to drive the next steps of the specification development process.
The PWD includes a significant number of documents covering:
•	the requirements agreed by the FWG;
•	specifications for various components of the formula specification;
•	normative schemas for the specifications; and
•	examples showing usage of the specifications.
2	Requirements
The requirements agreed upon by the FWG are included in the PWD.
The requirements have been agreed by the FWG after a systematic review of the previous Candidate Recommendation Formula Requirements [CRFR].  Since the previous PWD, the requirements have been augmented with explanations of their motivation and with use cases.  Much of this new material has drawn on the previous Candidate Recommendation Formula Requirements [CRFR].
3	Specifications
The formula specification has been modularised, resulting in a large number of relatively simple specification documents.
These documents depend on each other.  Indentations in the list of specifications below reflect the dependencies.
The set of specifications include:
The generic link specification 
The formula specification
The variable specification
The general filter specification
The concept filter specification
The period filter specification
The entity filter specification
The unit filter specification
The value filter specification
The dimension filter specification
The tuple filter specification
The unit filter specification
The generic label specification
The generic reference specification
Being a PWD, these specifications are not stable.  In particular, many of the XBRL functions referred to by the filter specifications have not yet been defined in a function specification.
Also note that the specifications in this PWD do not address more specialised usage patterns for formulae.  Specialised usage patterns will be addressed in extension specifications after the formula specification has stabilised.  Among these usage patterns, priority will be given to XBRL instance validation, tuple creation, and formula chaining.
4	Schemas
A range of XML documents are also included in the PWD.  These can be found in the xml directory in the ZIP file containing the PWD.
The xml directory contains a directory called core_schemas.  This directory contains the schemas that support the specifications in the PWD.  Each specification names the schemas that support it.  The names of the files in the core_schemas directory correspond to these schema names.
These schemas can be used to validate the examples provided in the xml/examples directory.
5	Examples
A small number of examples are included in the xml/examples directory.  As the specifications stabilise, excerpts from these examples may be included in the specification texts.  Until then, these examples provide the only illustrations of how the specifications work together to support the declaration of XBRL formulae.
The examples and their supporting documentation can be reviewed using a web-browser with XSLT support by opening the index.xml file in the xml directory.
6	Conformance suite tests
If released as a candidate recommendation, a conformance suite will also be included.  Each test in the conformance suite will have its own directory under the xml/tests directory.  No conformance suite tests are included in this PWD.
7	Focus issues
By publishing this PWD, the FWG is seeking feedback from software vendors with an interest in implementing some or all aspects of the formula and related specifications.
Most importantly, feedback is being sought on the following issues:
•	are the specifications straightforward to implement building on existing XBRL functionality?
•	are the specifications likely to result in formulae that will execute efficiently against large datasets?
•	will the specifications support an intuitive user interface?
More specific issues are raised in the following subsections.
Responses that are accompanied by explanations and use cases will be of particular value to the FWG when deciding how best to address the limitations of the current PWD.
7.1	Custom function signatures
The current PWD defines syntax for custom function signatures.  Custom function signatures have to be included in a formula link that uses custom functions in its XPath expressions.  A custom function signature documents a custom function, to some extent, but does not provide an implementation of the logic of the custom function.
See section 2.1.2 of the formula specification for further details.
•	What kinds of uses would you have for custom function signatures?
•	How burdensome would validation of formulae against the custom function signature requirements be?
7.2	Implicit filtering
The variable specification now defines two kinds of filters for fact variables: explicit filters, each of which is declared with XML mark-up, and implicit filters, that are implied by the previously evaluated fact variable.
See section 3.1.2.2 of the variables specification.
•	How clear are the rules for inference of implicit filters?
•	How easy would the implicit filtering mechanism be to implement?
•	Do you expect problems supporting implicit filters in a user interface?
7.3	Implied XPath expressions
Various strategies have been used throughout the specifications to define the XPath expressions that are implied by filters, in terms of the information content of the filters themselves.
•	Do you expect any of those XPath expression definitions difficult to interpret or to incorporate into an implementation of a formula processor?
7.4	Explicit filters
A broad range of explicit filters have been defined to cover many aspects of XBRL facts.  Do you expect any of these filters to be:
•	of limited value to formula authors;
•	excessively powerful;
•	confusing to users; or
•	redundant?
Are there explicit filtration rules that you think should be added to the existing filter specifications?
7.5	Normative schemas
Are the normative schemas going to support the kinds of optimisations that you expect will be necessary to drive efficient formula analysis and evaluation?
Should the common components of the syntax defined in the normative schemas be rationalised?
A.	References (non-normative)
[CRFR]	Walter Hamscher, Geoff Shuetrim, David vun Kannon
XBRL Formula Requirements, Candidate Recommendation, 2005-05-21
http://www.xbrl.org/SpecRequirements/ 

B.	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).
C.	Document History (non-normative)
Date	Editor	Summary	
2007-01-23	Geoff Shuetrim	First draft.	
2007-07-10	Hugh Wallis	Made amendments and corrections to prepare for release as with the July public working draft.	
2007-07-13	Geoff Shuetrim	Reviewed and responded to comments from Hugh Wallis.	
D.	Approval process (non‑normative)
This document will not be released as a part of any final recommendation.