Many of the standards that we deal with in the XBRL world are fearsomely complicated, take years to develop, and enable new and exciting ways of working.
This post is about a proposed standard that is very simple, took only a few hours to develop and which is just intended to make working with XBRL that little bit easier.
Taxonomies are a key part of XBRL. They typically consist of many files, hosted on a website somewhere, which are then referenced by the instance documents or extension taxonomies that use them. This creates two practical problems for people working with taxonomies.
Problem 1: Finding the Entry Points
Over time taxonomies have become increasingly complicated, and modular taxonomies consisting of tens, if not hundreds of files have now become the norm. In such a modular taxonomy, only a handful of those files are typically considered to be “entry points”, that is, files from which you would start the DTS discovery process.
For example, the full 2009 UK GAAP, IFRS, Banking and Charities taxonomies ZIP file consists of 603 files, but contains just four primary entry points. These are described in Word documents included in the ZIP file, which means in order to start working with the taxonomy I need to:
- Unpack the ZIP file
- Open and read the Word documents to decide which file inside the ZIP I actually need
- Open my XBRL software, browse to where I unpacked the ZIP file, and then browse to the right file inside the ZIP.
Wouldn’t life be just that little bit easier if I could just point my XBRL software at the ZIP, be presented with a list of the four entry points (with sensible, human readable descriptions), and then just open what I wanted? Something more like this:
Problem 2: Offline working
XBRL taxonomies are typically published on publicly available web servers, and then referenced by instance documents using an absolute URL. An XBRL processor consuming such a document will then follow the URL and download the files that make up the taxonomy as required. This creates two potential issues. Firstly, it means that you need an internet connection in order to process the document. Secondly, taxonomies are big (the UK taxonomies are made up of over 50MB of XML files) so you need a fast internet connection.
In order to support offline work, and to improve performance, you really want to be working with offline copies of taxonomies, rather than constantly downloading them from the web. Most XBRL software already provides some mechanism for working with offline copies of taxonomies.
At its simplest, software can just cache copies of taxonomies as it uses them, although that means that you’ve got to use it once before it becomes available for offline use, and the cache may be subject to an expiry policy to limit its size. In many cases it’s desirable to control explicitly which taxonomies are going to be stored locally, but this is often cumbersome to configure as you need to provide not only a copy of the taxonomy but also a “remapping” or “redirection” that specifies what public locations should be remapped to your local copy.
Wouldn’t life be just that little bit easier if I could just give my XBRL software a ZIP of the taxonomy, and it would configure itself for offline use, so that instance documents referencing that taxonomy would then “just work”?
The solution: Taxonomy Packages
Taxonomy Packages are a simple solution to the above problems that require only a minimal change in the way that taxonomies are currently distributed. Most taxonomies are already made available as ZIP files, containing all the files that make up the taxonomy. A Taxonomy Package is simply a ZIP file with an extra XML file dropped into it.
The XML file, called .taxonomyPackage.xml, provides a list of the entry points within the taxonomy, along with names and descriptions. The .taxonomyPackage.xml file also contains generic name, description and version meta-data about the taxonomy as a whole, enabling taxonomy distributions to be self-documenting. All names and descriptions have support for multi-language alternatives.
The other component of the .taxonomyPackage.xml is a set of remappings, that allow the contents of the ZIP file to be treated as if they were hosted at an internet location. At its simplest, a remapping could take the form of remapping the prefix “http://www.xbrl.org/uk/” to a directory within the ZIP file. This tells a processor that every time it encounters a URL starting with “http://www.xbrl.org/uk/” it should try to resolve it to an equivalently named file within the taxonomy package ZIP.
The format of the .taxonomyPackage.xml file has been kept as simple as possible. We’ve published some samples, and of course, a schema for the file format:
- A sample .taxonomyPackage.xml for the UK Taxonomies.
- The taxonomypackage.xsd schema.
- A complete Taxonomy Package for the UK Taxonomies
We will be publishing a simple spec on the details of how these files are to be processed just as soon as we’ve had a chance to write them down.
Working with Taxonomy Packages
As you will see from the comment at the top of the schema, we’re making this available under a Creative Commons licence that allows free use of the format (including for commercial purposes). Our hope is that the XBRL community will agree that this is a simple solution to a simple problem, and if we adopt a common solution then XBRL will become that little bit easier to work with, and just a little bit less intimidating for end users.
We’re actively introducing support for taxonomy packages into our products. The recent Magnify and SpiderMonkey 1.27 releases have support for opening packages, and SpiderMonkey 1.27 also has support for creating them.
If you would like more information on taxonomy packages, or would like to see a taxonomy package sample for your taxonomy, please drop me an email.