Rendering rules can be activated to obtain different views of a document. For instance, activating rendering rule quiet for an object is a convenient way of temporarily skipping over all occurrences of that object -activating quiet for object paragraph provides a thumb-nail view of a document by skipping all content. This is similar to skipping complex material when first reading a printed document.
We may skip instances of some objects entirely, e.g., source code; in other cases, we may merely defer the reading. This notion of delaying the rendering of an object is aptly captured by the concept of floating an object to the end of the enclosing unit. Typesetting systems like La)TeX permit the author to float all figures and tables to the end of the containing section or chapter. However, only specific objects can be floated, and this is exclusively under the control of the author, not the reader of the document.
AsTeR provides a much more general framework for floating
objects. Any object can be floated to the end of any enclosing
hierarchical unit -instances of object footnote can be
floated to the end of the containing paragraph. The ability to
float objects is useful when producing audio renderings, since
audio takes time, and delaying the rendering of some objects
provides an overview.