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In this paper we describe the current approach to using MathML within Tagged PDF to enhance the accessibility of mathematical (STEM) documents. While MathML is specified by the PDF 2.0 specification as a standard namespace for PDF Structure Elements, the interaction of MathML, which is defined as an XME vocabulary, and PDF Structure Elements (which are not defined as XME) is left unspecified by the PDF standard. This has necessitated the development of formalizations to interpret and validate PDF Structure Trees as XME, which are also introduced in this paper.

In this application note we outline the goals of the "LATEX Tagged PDF" project, describe its current status, show how it can already now been used to create accessible and reusable PDFs, and outline our future plans for a successful completion. Further information can be found at https://latex3.github.io/tagging-project/.

This paper presents an extension to the general framework for globally optimized pagination described in Mittelbach (2016). The extended algorithm supports automatic placement of floats as part of the optimization. It uses a flexible constraint model that allows for the implementation of typical typographic rules that can be weighted against each other to support different application scenarios. By "flexible" we mean that the rules of typographic presentation of the content of a document element are not fixed---but neither are they completely arbitrary; also, some of these rules are absolute whereas others are in the form of preferences. It is easy to see that without restrictions the float placement possibilities grow exponentially if the number of floats has a linear relation to the document size. It is therefore important to restrict the objective function used for optimization in a way that the algorithm does not have to evaluate all theoretically possible placements while still being guaranteed to find an optimal solution. Different objective functions are being evaluated against typical typographic requirements in order to arrive at a system that is both rich in its expressiveness of modeling a large class of pagination applications and at the same time is capable of solving the optimization problem in acceptable time for realistic input data. Frank Mittelbach. 2016. A General Framework for Globally Optimized Pagination. In Proceedings of the 2016 ACM Symposium on Document Engineering (DocEng '16). ACM, New York, NY, USA, pages 11--20.

Pagination problems deal with questions around transforming a source text stream into a formatted document by dividing it up into individual columns and pages, including adding auxiliary elements that have some relationship to the source stream data but may allow a certain amount of variation in placement (such as figures or footnotes).