Multiple desc Elements
This page proposes allowing multiple desc elements inside info elements. The desc elements would allow type and role attributes. Processing tools would select the appropriate desc element using a similar algorithm to that used to select titles.
This proposal is still under consideration. Revisions may still be made based on your input. Discuss this proposal on mallard-list.
Mallard allows you to have multiple title elements in an info element. These info title elements can take type and role attributes. Users can provide different titles to be used in different situations. However, the same desc element is always used.
When it is useful to provide different titles for links, it may also be useful to provide different accompanying descs. With this proposal, you would be able to provide alternate descs with alternate titles.
This page proposes allowing zero or more of the mal_info_desc pattern in mal_info_content, and changing the mal_info_desc_attr pattern to allow optional type and role attributes, mirroring those attributes on the info title element.
When a desc element is needed for link text for a links element (or, rarely, for a link element), a processing tool would look up a desc element using the new lookup rules defined in MEP-0018: Type-and-Role Data.
Note that info titles can also be used to provide titles for sorting, for text-only environment, and for other purposes that may be defined by extensions, implementations, or future specifications. There is less utility in these for desc elements, but the same mechanism for specifying multiple values exists if needed.
Prior to the introduction of MEP-0008, this proposal had its own set of rules that required a type attribute along with roles for link descs. We also considered not using a type attribute. The lookup roles in MEP-0008 allow either method.
Compatibility and Fallback
This proposal makes no backwards-incompatible changes. Any page written in a version prior to the implementation of this proposal will work exactly the same in a processing tool that implements this proposal.
The fallback behavior for a new info element is that it is ignored. However, if there are multiple desc elements, the behavior of a Mallard 1.0 processing tool is undefined when selecting the desc element for link text. A Mallard 1.0 processing tool could reasonably select any desc at random, or even the concatenation of them all. All known implementations select the first desc element if there are multiple. When using multiple desc elements, you sould place the fallback desc first for the best fallback behavior with older implementations.
Comparison to Other Formats
No other format has a comparable mechanism for selecting page descriptions or other data.