IMS Candidate Final / Public Draft
Open Badges Baking Specification
IMS Candidate Final / Public Draft
|Date Issued:||08 March, 2017|
|Status||IMS Candidate Final / Public Draft|
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Documents Name: Open Badges Baking Specification
Revision: 08 March 2017
Status of this Document
This document is a Candidate Final / Public Draft of the Open Badges 2.0 specification, released on 08 March 2017 by IMS Global Learning Consortium. The specification will be considered final when approved by the IMS Technical Advisory Board and published as Final Release by IMS Global.
What Is Badge Baking?
Open Badges may be transmitted as image files with badge Assertions encoded within. This allows Open Badges to be portable wherever image files may be stored or displayed. Each Assertion expresses verifiable information about an individual’s achievement.
Badge Baking is the process of taking an Assertion and embedding it into the badge image, so that when a user displays a badge on a page, software that is OpenBadges-aware can automatically extract that Assertion data and perform the checks necessary to see if a person legitimately earned the badge. The BadgeClass image must be in either PNG or SVG format in order to support baking.
iTXt chunk should be inserted into the PNG with keyword
openbadges. The text can either be a signed badge assertion or the raw JSON for the OpenBadges assertion. Compression MUST NOT be used. At the moment, language tag and translated keyword have no semantics related to badge baking.
An example of creating a chunk (assuming an iTXt constructor):
An iTXt chunk with the keyword “openbadges” MUST NOT appear in a PNG more than once. When baking a badge that already contains OpenBadges data, the implementor may choose whether to pass the user an error or overwrite the existing chunk.
Parse the PNG datastream until the first
iTXt chunk is found with the keyword
openbadges. The rest of the stream can be safely discarded. The text portion of the iTXt will either be the JSON representation of an OpenBadges assertion or a signature.
The pre-specified behavior of badge baking worked differently. Instead of baking the whole assertion or signature into an
iTXt:openbadges chunk, the URL pointing to the hosted assertion was baked into a
tEXt:openbadges chunk. In order to get the full assertion, an additional HTTP request must be made after extracting the URL from the
First, Add an
xmlns:openbadges attribute to the
<svg> tag with the value “http://openbadges.org”. Directly after the
<svg> tag, add an
<openbadges:assertion> tag with a
verify attribute. The value of
verify should either be a signed OpenBadges assertion or the URL from
verify.url in the badge assertion.
If a signature is being baked, no tag body is necessary and the tag should be self closing.
If an assertion is being baked, the JSON representation of the assertion should go into the body of the tag, wrapped in
An example of a well baked SVG with a hosted assertion:
There MUST be only one
<openbadges:assertion> tag in an SVG. When baking a badge that already contains OpenBadges data, the implementor may choose whether to pass the user an error or overwrite the existing tag.
Parse the SVG until you reach the first
<openbadges:assertion> tag. The rest of the SVG data can safely be discarded.
If the tag has no body, the
verify attribute will contain the signature of the badge. If there is a body, it will be the JSON representation of a badge assertion.
Baking Specification Changelog
2017-02-13 Version 1.0.0
- Update SVG example to use Open Badges 2.0 syntax
- Fix typo in introduction
2013-11-05 Version 1.0.0
- Support for full assertions added
- Support for signed badges added
- Support for SVGs added
- PNG baking now uses
- Only PNGs supported:
tEXtchunk used with keyword
- Only hosted badges supported
- Hosted URL embedded in PNG