\chapter{Introduction}\label{Introduction}

Early electronic document formats such as PostScript were motivated by a need to print documents onto a paper medium. In the PostScript standard, this lead to a model of the document as a program; a series of instructions to be executed by an interpreter which would result in ``ink'' being placed on ``pages'' of a fixed size\cite{plrm}. The ubiquitous Portable Document Format (PDF) standard provides many enhancements to PostScript taking into account desktop publishing requirements\cite{cheng2002portable}, but it is still fundamentally based on the same imaging model\cite{pdfref17}. This idea of a document as a static ``page'' has lead to limitations on what could be achieved with a digital document viewers \cite{hayes2012pixels}.

%The emergence of the internet, web browsers, XML/HTML, JavaScript and related technologies has seen a revolution in the ways in which information can be presented digitally, and the PDF standard itself has begun to move beyond static text and figures\cite{hayes2012pixels, barnes2013embedding}. However, the popular document formats are still designed with the intention of showing information at either a single, fixed level of detail, or a small range of levels.

As most digital display devices are smaller than physical paper medium, all useful viewers are able to ``zoom'' to a subset of the document. Vector graphics formats including PostScript, PDF and SVG support rasterisation at different zoom levels\cite{plrm, pdfref17, svg2011-1.1}, but the use of fixed precision floating point numbers causes problems due to imprecision either far from the origin, or at a high level of detail\cite{goldberg1991whatevery, goldberg1992thedesign}.

There are many possible applications for documents in which precision is unlimited. Several areas of use include: visualisation of extremely large or infinite data sets; visualisation of high precision numerical computations; digital artwork; computer aided design; and maps.

We have implemented a proof of concept document viewer compatable with a subset of the SVG standard, which has allowed us to explore the limitations of floating point arithmetic and possible approaches to achieving arbitrary precision document formats. Using the Rational representation of the GNU Multiple Precision (GMP) library\cite{granlund2014GMP} we are able to implement correct rendering of SVG test images seperated by arbitrary distances. We demonstrate the trade off between performance cost and the accuracy of rendering
