Higher-level layout through topological abstraction

Existing layout languages provide support for geometric properties allowing - and in a sense forcing - users to give a complete geometric description of the desired output: if the characteristics of the output medium change, the layout of the whole document has to be reworked completely, as the properties set by the user are no longer appropriate for the modified context. In this paper we propose a different paradigm which allows users to produce layouts by describing their topological and abstract properties, rather than geometric ones. We first define and detail topological properties as abstract relationships between the document components, independent from the output characteristics, and then describe an XML-based layout language based on these concepts, called TALL. A running engine able to transform topological layouts into actual PDF files, based on XSLT and the DDF framework, is presented as well.