IMSC Hypothetical Render Model is a W3C Proposed Recommendation

Today the Timed Text Working Group published IMSC Hypothetical Render Model as a W3C Proposed Recommendation. This specification specifies an Hypothetical Render Model (HRM) that constrains the presentation complexity of documents that conform to the Text Profiles specified in any edition of Internet Media Subtitles and Captions ([IMSC]).

The model is not intended as a specification of the processing requirements for implementations. For instance, while the model defines glyph cache for the purpose of modelling how the number of glyph drawing operations can be reduced, it neither requires the implementation of such a cache, nor models the sub-pixel glyph positioning and anti-aliased glyph rendering that can be used to produce text output. Furthermore, the model is not intended to constrain readability complexity.