Requirement and Solution Matrix

Requirement	longdesc	aria- describedat	aria- describedby	canvas	figcaption	href	details	iframe	imagemap	New HTML Attr	rel="longdesc"
No forced visual encumbrance	Pass	Fail [3]	Fail	Fail	Fail	Fail	Fail	Fail	Pass	Fail [3]	Fail
Discoverability tools exist. when there is no forced visual encumbrance.	Pass	Fail [3]	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail [3]	Fail
Programmatically ties a set of structured content that is external to the document to an <img> element.	Pass	Fail [3]	Fail	Fail	Fail	Fail [1]	Fail	Pass	Pass	Fail [3]	Pass
Programmatically determinable when an image already has a link which is mapped to go to another page or a larger image.	Pass	Fail [3]	Pass	Fail	Pass	Fail	Pass	Pass	Fail	Fail [3]	Fail
Provides easy reuse of the targeted description from multiple sources.	Pass	Fail [3]	Fail	Fail	Fail	Fail [1]	Fail	Pass	Pass	Fail [3]	Pass
Provides the choice to consume. As currently implemented, the description is not forced upon screen reader users.	Pass	Fail [3]	Fail	Fail	Fail	Fail [1]	Fail	Unknown [4]	Unknown [4]	Fail [3]	Unknown [4]
Does not require reengineering ARIA.	Pass	Fail	Fail	Pass	Pass	Pass	Pass	Pass	Pass	Pass	Pass
Is not a bridging technology.	Pass	Fail	Fail	Pass	Pass	Pass	Pass	Pass	Pass	Pass	Pass
Provides WYSIWYG tool support for authors of limited skill set.	Pass	Fail [3]	Fail	Unknown [4]	Unknown [4]	Pass	Unknown [4]	Pass	Pass	Fail	Fail
Does not force people to read another large specification.	Pass	Fail [3]	Fail	Pass	Pass	Pass	Pass	Pass	Pass	Pass	Pass
Provides ease of use.	Pass	Fail [3]	Fail	Fail	Fail	Fail [1]	Fail	Pass	Pass	Fail [3]	Unknown [4]
Provides ease of authoring.	Pass	Fail [3]	Fail	Fail	Fail	Fail [2a]	Fail	Fail	Fail	Fail [3]	Unknown [4]
Provides native HTML long description semantics.	Pass	Fail	Fail	Fail	Fail	Fail [2]	Fail	Fail	Fail	Fail [3]	Pass
Provides backwards compatibility and no need to retrofit.	Pass	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail
Is recognized by existing authoring tools, user agents, assistive technologies.	Pass	Fail	Fail	Fail	Fail	Fail	Fail	Pass	Unknown [4]	Fail	Fail
Numerous tutorials and documentation throughout the world explain how to use this technique for complex image descriptions.	Pass	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail
Is law in various countries.	Pass	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail
Is a standard in numerous organizations and companies.	Pass	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail
Is policy in many organizations and companies in throughout the world.	Pass	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail
Is in numerous guidelines throughout the world.	Pass	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail
Does not reinvent the wheel.	Pass	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail
Provides solution to all specific use cases.	Pass	Fail [3]	Fail	Fail	Fail	Fail	Fail	Fail	Fail	Fail [3]	Fail

The only solution that meets all requirements and fullfills all specific use cases is longdesc.

Notes

[1] Fails whenever link is used for another function. And it is not automatically announced to users of screen readers like JAWS, SuperNova/Hal or WindowEyes that a long description is available.

[2] Fails because link semantics are already well-defined.

[2a] To provide proper semantics rel="longdesc" would be needed. But rel="longdesc" is not implemented by existing tools.

[3] This proposed solution fails as it is neither formally specified or nor implemented.

[4] Unknown. No evidence presented.