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diff --git a/usergrps/uktug/baskervi/5_2/barron.tex b/usergrps/uktug/baskervi/5_2/barron.tex new file mode 100644 index 0000000000..7407520bbd --- /dev/null +++ b/usergrps/uktug/baskervi/5_2/barron.tex @@ -0,0 +1,164 @@ +\title{Portable Documents: Why Use SGML?} +\author[David Barron]{David Barron\\ +Department of Electronics and Computer Science\\ +University of Southampton} +\begin{Article} +\section{Introduction} +In this article we present a few ideas as a framework for the +discussion of portable documents. We address a number of questions: +\begin{itemize} +\itemsep 0pt plus .4pt +\item What are portable documents? +\item Who needs them, and why? +\item How to produce them, now and in the future +\end{itemize} + +\section{Documents} +Traditionally, a document was a file (or a deck of cards), +and consisted solely of text. +Today, documents are typically {\em compound}, a +mixture of text and graphics (bit-map or line art) that can be +rendered on paper or screen. Additionally, they may include +hypertext links (in which case they can only be viewed on screen). +A recent development is the ability to incorporate video +and sound in a compound document, either embedded +within the document or linked by a pointer: +such a document is a {\em multimedia} document. Hypertext-style links +may also be included to form a {\em hypermedia} document: evidently, +multimedia and hypermedia documents can only be `read' on a suitably +equipped computer system. + +World Wide Web (WWW) documents are a special case of +compound hypermedia documents +where the links are to other documents elsewhere on the Internet. +They can be regarded as virtual documents, in the sense that the +whole document never exists as a single identifiable object. +More generally, we can define a {\em virtual document} as +a structured collection of information from which instances of +documents and other resources can be derived. Examples include: +\begin{itemize} +\item The Oxford English Dictionary which exists as a database +from which are derived various printed editions (Shorter, Concise, +Pocket etc.), as well as the CD-ROM version +\item Critical editions of a literary text, where a single source +`document' contains all the variations, and can be printed out using +different variants as the base text +\end{itemize} + +\section{Portability} +The definition of portability that we shall use in this discussion is +the ability to transmit the document digitally (over a network, +or on a disk or CD-ROM) and re-create a faithful rendering of the document +after transmission, if need be +on a different hardware and/or software platform +from that on which the document was originally created. +It is important to observe that there are three different forms in +which the text and graphics in a document might be re-created: +\begin{itemize} +\item with absolute visual fidelity +\item with approximate visual fidelity +\item retaining content only +\end{itemize} + +\section{Who needs portable documents, and why?} + +Three different needs for portable documents can be adduced +\begin{enumerate} +\item Publishers need them in order to distribute electronic +books and journals +\item Communities with common interests +who need to share information need them. An example is a +scientific research community whose members use diverse hardware and +software +\item Librarians responsible for digital archives need +portable documents, since they cannot assume that a particular +hardware/software platform will exist in perpetuity +\end{enumerate} + +\section{Examples of successful portability} +\begin{itemize} +\item Computer science researchers and software manufacturers +distribute documents as PostScript files. This works well +if the fonts employed are restricted to the basic 35, and +the use of Adobe Acrobat (pdf files) increases portability when other +fonts are used. + +\item The Physics pre-print library at Los Alamos National Laboratory +is used by many physicists world-wide: over 10,000 retrievals per day +are reported. The archive holds pre-prints in \LaTeX\ and PostScript +formats (figures in PostScript only). This is successful because the +Physics community has for some years used \TeX\ as its preferred means +of exchanging information. + +\item WWW documents are highly portable, since +their rendering is (almost entirely) determined by the +browser software, and the use of a common mark-up language (HTML) +ensures portability +\end{itemize} + +\section{Achieving portability} +At first sight it appears that portability might be achieved by +agreeing standards (e.g. \LaTeX, PostScript, ODA, HTML). At present +there is too much choice, and no obvious winner, especially in +hypermedia documents. This is a sign of an immature technology. +Another important fact to take into account is that it is difficult to +impose standards in some environments (e.g., academia) where personal +preferences lead to the equivalent of religious wars. + +Particular problems in achieving portability arise from varying +fonts and character codes e.g. in handling European languages. +Unicode will go a long way towards solving the character +codes problem. + +\section{Why use SGML?} +SGML provides a formal and portable definition of document structure. +SGML syntax can define a hierarchical structure of embedded document parts, +and can associate a type with each component in the hierarchy. +By associating a rendering definition with each type of component, +it is possible to achieve a portable document. In particular, +SGML provides a uniform archive format for a library of portable +documents. + +\subsection{An example} +Suppose it is required to maintain a library of technical +documents in an environment where some authors use \LaTeX, +whilst others use Microsoft Word. We can define an SGML +DTD for the document structure, together with \LaTeX\ and Word +styles to define the rendering. +This opens up three possibilities: +\begin{enumerate} +\item Author in SGML and use a tool to produce a \LaTeX\ or +Word version from which the printed version can be produced +\item Author in \LaTeX\ and use a tool to translate to SGML to +produce the archive copy +\item Author in Word and use a tool to translate the RTF form to +SGML to produce the archive copy. +\end{enumerate} + +In addition to the SGML version of the documents, the +archive must contain the Word and \LaTeX\ style files and the +translation tools. Once this is done, anyone can collect a +document, the required style files and tools and produce a copy of +the document. +This will of course only work for text documents. For any +document with graphics content, and for hypermedia +documents, more is required. This is possible in +principle, but much remains to be done + +\section{The future} +A combination of SGML and OpenDoc is probably the best way forward. +OpenDoc provides an architecture for portable documents: +it treats a +document as a container for a collection of `parts', each of which can +have other parts embedded within it. Each type of part has +associated programs to edit and render it, so that +documents can be re-created with varying degrees of fidelity +depending on the availability of rendering software +for the particular varieties of parts that it includes. + +OpenDoc is a dynamic architecture, and assumes that a new type +of part may occur at any time. +In principle SGML can be used to describe the static +structure of an OpenDoc document, providing the final link in the +portability chain. +\end{Article} |