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author | Norbert Preining <norbert@preining.info> | 2019-09-02 13:46:59 +0900 |
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committer | Norbert Preining <norbert@preining.info> | 2019-09-02 13:46:59 +0900 |
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tree | 60335e10d2f4354b0674ec22d7b53f0f8abee672 /usergrps/uktug/baskervi/5_2/flynn.tex |
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diff --git a/usergrps/uktug/baskervi/5_2/flynn.tex b/usergrps/uktug/baskervi/5_2/flynn.tex new file mode 100644 index 0000000000..9704340756 --- /dev/null +++ b/usergrps/uktug/baskervi/5_2/flynn.tex @@ -0,0 +1,498 @@ +% this is from the Companion, p108, but simply doesn't work! +% In the tabular, LaTeX complains that \temp is undefined. +\newcommand{\PreserveBackslash}[1]{\let\temp=\\#1\let\\=\temp} +\let\PBS=\PreserveBackslash +% This ought to be a package, but I don't think it's been unpgraded yet. +\title{HTML \& \TeX: Making them sweat} +\author[Peter Flynn]{Peter Flynn\\University College, Cork} +\begin{Article} +\begin{abstract} + +\noindent HTML is often criticised for its presentation-oriented conception. +But it does contain sufficient structural information for many +everyday purposes and this has led to its development into a more +stable form. Future platforms for the World Wide Web may support other +applications of SGML, and the present climate of popularity of the Web +is a suitable opportunity for consolidation of the more stable +features. \TeX\ is pre-eminently stable and provides an ideal +companion for the process of translating HTML into print. + +\end{abstract} + +\section{Markup} + +HTML, a HyperText Markup Language\cite{html-spec}, is the language used +to structure text files for use in the World Wide Web, an Internet-based +hypertext and multimedia distributed information system. HTML is an +application of SGML, the Standard Generalized Markup Language, ISO +8879\cite{iso-sgml}. Contrary to popular belief, neither SGML nor HTML +is new: SGML gained International Standard status in 1986 and HTML has +been in use since 1989. +\begin{figure*} +\begin{verbatim} +#! /bin/sh + +echo Content-type: text/html +echo + +cat <<EOH +<html><head><title>Date and time</title></head><body><p>It is now +EOH +date +cat <<EOT +</p></body></html> +EOT +\end{verbatim} +\caption{Example of a Unix shell script to return the date and time as +a HTML file} +\label{script} +\end{figure*} + +SGML is a specification for writing descriptions of text structure. In +itself SGML does not \emph{do} anything, any more than, say, Kernighan +and Ritchie's specification of the C~language\cite{krc} \emph{does} +anything: users and implementors have to do something \emph{with} +it. It has been slow to achieve popularity, partly because writing +effective Document Type Descriptions (DTDs) is a non-trivial task, and +partly because software to make full use of its facilities has +traditionally been expensive. It was therefore seen as a `big business +only' solution to text-handling problems until the popularisation of +HTML owing to increased use of the World Wide Web. Since 1992 the +software position has also improved considerably~--- an extensive list of +tools is maintained by Steve Pfeffer at UIO\cite{sgml-tools}. + +\section{The World Wide Web} + +WWW (W3 or just `the Web') is a client-server application on the +Internet. Users' clients (`browsers') request files from servers run +by information providers and display them, using the HTML markup +embedded in the text to render the formatting. Some of the markup can +provide filenames for the retrieval of graphics as illustrations, or +act as anchor-points for links to other documents, which can be +further text, or graphics, sound or motion video. This latter +capability gives the Web a hypertext and multimedia dimension, and +allows crosslinking of files almost anywhere on the Internet. + +Because the HTML files are plain text with embedded plain text markup, +in traditional SGML manner, they are immediately portable between +arbitrary makes and models of computer or operating system, making the +Web one of the first genuinely portable, multiplatform applications of +its kind. + +\subsection{HTML Markup} + +An example of simple markup and an appropriate rendering is +illustrated in Figure~\ref{html-example}. The conventions of SGML's +Reference Concrete Syntax\cite{iso-sgml} are used, so markup `tags' +are enclosed in angle brackets (less-than and greater-than signs), in +pairs surrounding the text to which they refer, with the end-tag being +preceded by a slash or solidus immediately after its opening angle +bracket. + +\begin{figure*} +\begin{verbatim} +<html> + <head> + <title>Fleet Street Eats</title> + </head> + <body> + <h1>Where to eat in Fleet Street</h1> + <p>There are many restaurants in the City, from + fast-food joints to <i>haute cuisine</i>.</p> + ... +\end{verbatim} +\vspace{1ex} +\hrule +\vspace{1em} +\begin{flushright} +\begin{small} +{\bf Document title:} {\tt Fleet Street Eats} +\end{small} +\end{flushright} +\section*{Where to eat in Fleet Street} +There are many restaurants in the City, from +fast-food joints to {\it haute cuisine\/}.\newline\dots +\caption{Example of HTML markup and possible rendering} +\label{html-example} +\end{figure*} + +The rendering is left almost entirely to the user's client program, as +there are almost no facilities within HTML for the expression of +appearance apart from a minimal indication of font change (italics, +boldface and typewriter-type). Indeed, most recent browsers allow the +{\em user} arbitrary control over which fonts, sizes and colours +should be used to instantiate the tagged elements of text. + +\subsection{Implementation} + +HTML was devised for the Web by non-SGML-experts who saw it as an +ideal mechanism for implementing plain-text portability while +preserving sufficient structural information for online rendering: one +of the classical reasons for adopting SGML. It is now becoming +standardised by an IETF working group who have produced a draft +specification in the form of a formal DTD\cite{html-spec}. Because of +the need to allow this specification to model existing `legacy' +documents (most of which would be regarded as fragments rather than +document instances), as well as provide for more robust usage, the +current DTD has two modes: a non-rigorous `deprecated' mode for +describing the legacy and a `recommended' mode for creating and +maintaining files in conventional form. + +HTML is sufficient for minimal documents, providing the structural and +visual features shown in Figure~\ref{html-tags}. A future version +(3.0) is being developed by the IETF Working Group, which will allow +the description of mathematics, tables and some additional visual- and +content-oriented features. + +\begin{figure*} +\begin{tabular}{>{\tt}l>{\PBS\raggedright\hspace{0pt}\baselineskip=10pt}p{1in}|>{\tt}l>{\PBS\raggedright\hspace{0pt}\baselineskip=10pt}p{1in}|>{\tt}l>{\PBS\raggedright\hspace{0pt}\baselineskip=10pt}p{1in}} +\multicolumn{2}{c|}{{\bf Structural}}&\multicolumn{2}{c|}{{\bf Descriptive}}&\multicolumn{2}{c}{{\bf Visual}} \\ [3pt] +html &document type& + a &hypertext link anchor-point& + b &bold type \\ +\quad head &document header& + cite &citations& + br &forced line-break \\ +\quad title &document title& + code &computer code& + hr &horizontal rule \\ +\quad base &root address for incomplete hypertext references& + em &emphasis& + i &italics \\ +\quad meta &specification of mapped headers& + kbd &keyboard input& + tt &typewriter type \\ +\quad link &relationship of document to outside world& + samp &sample of input& + img &illustrations \\ +\quad isindex &specifies a processable document which can take an argument& + strong &strong emphasis& + &\\ + && + var &program variable& + &\\ +body &contains all the text& + && + &\\ +\quad h1\dots h6&six levels of section heading& + && + &\\ +\quad p ¶graph& + && + &\\ +\quad pre &preformatted text& + && + &\\ +\quad blockquote&block quotations& + {\bf Form-fill}&& + {\bf Obsolete:}&\\ +\quad address &addresses& + form &contains a form& + listing &use {\tt pre} \\ +\quad ol &ordered lists& + textarea &free-text entry & + xmp &use {\tt pre} \\ +\quad ul &unordered lists& + input &input field (text, checkbox, radio button, {\it etc}& + plaintext &use {\tt pre} \\ +\quad menu &menu lists& + select &drop-down menu& + nextid &editing control \\ +\quad dir &directory lists& + \quad option &menu item& + dfn &definition of term\\ +\qquad li &list item& + && + &\\ +\quad dl &definition lists& + && + &\\ +\qquad dt &definition list term& + && + &\\ +\qquad dd &definition list description& + && + &\\ +\end{tabular} +\caption{Markup available in HTML 2.0 (indentation implies the item +must occur within the domain of its [non-indented] parent)} +\label{html-tags} +\end{figure*} + +Despite the coming improvements, HTML is likely to be joined in the +Web by other DTDs in future. One well-known SGML software house +already has a prototype browser which can handle instances of +arbitrary DTDs, given sufficient formatting information. This would +make it possible to use the Web for transmission and display of +documents using other SGML applications such as CALS (US Military), +DocBook (O'Reilly/Davenport), the TEI (Text Encoding Initiative) and +corporation-specific DTDs (such as those of Elsevier).\label{otherdtds} + +The next version of the DTD, HTML3, contains specifications for +mathematics, tables and some additional elements for +content-descriptive material, as well as a few extra visual keys such +as an {\tt ALIGN} attribute for positional specification. Most of this +work is being implemented on a test basis in the Arena browser (Unix/X +only at the moment) at CERN. + +Although Web browsers can reference files by any of several methods +(HTTP, the Web's `native' protocol; FTP; Telnet; Gopher; WAIS; and +others) by using the URL (Universal Resource Locator: a form of file +address on the Internet), the most powerful tool lies at the server +end: the ability of servers to execute scripts, provided their output +is HTML. A trivial example is shown in Figure~\ref{script}, which +returns the date and time. + +Such a script can contain arbitrary processing, including the +invocation of command-line programs and the passing of arguments. Data +can be gathered from the user either with the \verb+<isindex>+ tag in +the header, which causes a single-line data-entry field to appear, or +with the more complex \verb+<form>+ element with scrollable text +boxes, checkboxes, radio buttons and menus. In this manner, complete +front-ends can be manufactured to drive data-retrieval engines of any +kind, provided that they operate from the command line, and that the +script returns their output in HTML\@. The user (and the browser) remain +unaware that the result has been generated dynamically. + +\subsection{Presentation} + +HTML is criticised for being `presentation-oriented', but as can be +seen from Figure~\ref{html-tags}, the overwhelming majority of the +markup is structural or content-descriptive. However, this does not +prevent the na\"\i ve or sophisticated author from using or abusing +the markup in attempts to coerce browsers into displaying a specific +visual instantiation, primarily because none of the browsers (with the +partial exceptions of Arena and {\tt w3-mode} for GNU Emacs) performs +any form of validation parsing, and will thus display any random +assemblage of tags masquerading as HTML. This behaviour has misled +even some eminent authorities to dismiss HTML as `not being SGML'. + +There is thus a conflict between the SGML purist on the one side, who +decries any attempt at encoding visual appearance; and the uninformed +author on the other, who has been unintentionally misled into thinking +that HTML and the Web constitute some kind of glorified networked DTP +system. + +The purists are few in number but eloquently vocal: however, in +general, they acknowledge that visual keys can be included if they are +carefully coded. A perceived requirement to allow an author to +recommend the centering of an element is thus achieved in HTML3 by the +\verb+align="center"+ attribute, rather than the unnecessary +\verb+<center>+ element proposed by the authors of Netscape. + +The demands of the author are at their most marked in the approach of +publishers and marketing users, who have been accustomed for the last +550 years to exert absolute control over the final appearance of their +text. But the Web is not paper, and the freedoms and constraints of +the Press do not apply: it is as much a new medium as radio or +television. For such an author to insist that she must be able to +control the final display to the same extent as on paper is as +pointless as insisting that a viewer with a black-and-white television +must be able to see the colours in a commercial. + +The paradigm has been established that the browser controls the +appearance, using the markup as guidelines. There is indeed no reason +at all why attributes could not be added so that an author could write + +{\tt <h1 color=green font=LucidaBrightBoldItalic size=24 shading=50>} + +\noindent but the user of Lynx or WWW (two popular text-only browsers +for terminal screens) would still only see the heading in fixed-width +typewriter characters. The habit of insisting that everyone `must' +see a particular typographic instantiation is an unfortunate result of +a misinterpretation of the objective of the Web: to deliver +information in a compact, portable and arbitrarily reprocessable form. + +But publishers accustomed to paper, insistent on `keeping control', +have of course an entirely valid point, one with which the present +author has great sympathy. Why should a carefully-prepared document be +made a hames of by a typographically illiterate user who has set +\verb+<h2>+ to display as 44pt Punk Bold in diagonal purple and green +stripes? + +The solution probably lies in the implementation of style sheets, +perhaps along the lines of those discussed by the authors of +Arena\cite{arena-style}. They would in any case only be +recommendations: not every user has a CD-ROM of Adobe or Monotype +fonts. In any event, if 100\% control is essential, as in the display +of typographic examples, all graphical browsers can be configured to +spawn a window to display PostScript file, although the download time +may be a strong disincentive. + +It is entirely possible that the control of content will +ultimately prove a more attractive option than the control of +appearance. + +\section{Publishing with HTML} + +Setting aside the unresolved questions of display, there are more +pressing business problems about publishing on the Web. + +The authentication of users is being addressed at several levels, from +simple, non-authoritative checks using {\tt identd} to the more complex +username-and-password systems employed on some Web pages. From the +user's end, the authentication of the data being accessed is equally +important. The openness of the Internet in its raw form allows +`spoofing' in both directions, so the emergence of protocols to +provide checks is to be welcomed. + +The security of network-accessible texts from break-ins remains a +concern to anyone providing high-value merchandise, and Web text is +in this sense no different from any other computer data. Normal +precautions must therefore be taken to prevent theft through +other channels (such as remote lo\-gin), as distinct from theft +perpetrated by falsification of Web access. + +There is a need for robust solutions to charging and billing for +usage, and the secure transmission of financial data, including credit +card numbers, digital signatures, and perhaps even EFT transactions. +The Secure HTTP (SHTTP) mechanism being marketed by MCom and others is +becoming popular as a way of achieving some of this, but the Internet +must shed some of its image of lax controls and sloppy housekeeping if +it is to achieve sufficient `respectability' to attract the business +of those who are not networking specialists. + +The handling of copyright and the intellectual property of electronic +texts remains, as ever, an unsolved problem. While copyright law can +be used to provide a remedy for breach, the difficulty lies in +preventing the breach occurring in the first place. The reason is that +(as with other electronic mat\-er\-ial), copying and reproduction is fast, +cheap and easy, once the material is in the hands of the customer. +While a supplier may use SHTTP to protect the details of the +transaction, once a print file has been sent to someone, the supplier +retains no control whatsoever over its use, reuse and abuse. Copies +could be sent to dozens others, or printed many times, in the space of +minutes. + +\subsection{Printing from HTML} + +The demand for printed copies of Web material is surprisingly high. +Although in some cases it is reminiscent of those people who insist on +printing their email, it is undeniable that there is a serious +requirement for good quality print from Web documents. + +Existing solutions to printing SGML text are usually +application-specific, being embedded in SGML editors or DTP systems, +but there are also some more generic packages: + +\begin{itemize} + +\item {\tt Format} by Thomas Gordon (\LaTeX) + +\item {\tt HTMLtoPS} by Jan K\aa rrman (PostScript) + +\item {\tt SGML2TeX} and {\tt WebSet} by Peter Flynn (\TeX/\LaTeX) + +\item {\tt SimSim} by Jonathan Fine (\TeX) + +\end{itemize} + +\noindent The use of \TeX\ systems for most of these seems to indicate +that the similarity of markup concepts has not gone unnoticed by +practitioners. The author's own contributions are experimental, but +the second of them is planned as an interactive Web service, to be +introduced in the summer of 1995. Emailing a URL to the point of +service will cause it to be retrieved, typeset, and the output +returned to the user by email in PostScript form. As a form of email +browser, the control of appearance may lie in the hands of the +user, but suggestions for how implement this are currently +being sought\cite{ttn41}. + +\subsection{Problems} + +Implementing a professional level of typesetting from HTML raises some +interesting questions: + +\begin{itemize} + +\item most HTML files are invalid + +\item most HTML authors don't understand SGML + +\item most HTML authors couldn't care less + +\item most World Wide Web users couldn't care less + +\end{itemize} + +The handling of missing, damaged or abused tags in a gracious manner +is not a feature of most SGML parsers. At the best, a +typesetter-browser can only be expected to report to the user that a +file is invalid, and while it may be displayed by browsers which do +not make any claim to typographic quality, an attempt to make a +respectable print job of an invalid file is unlikely to succeed. + +\section{Development} + +The future of the World Wide Web and HTML is uncertain. While +development continues, and while new users are anxious to start +surfing the net, the existing designs and implementations will +suffice. In the longer term, a coalescing of services is likely to +occur, but for this to happen, a number of changes need to take place: + +\begin{itemize} + +\item The Web will start to make use of other DTDs, as outlined above. + Any file containing a \verb+<!doctype...>+ at the beginning could + cause a browser to retrieve the DTD specified, along with a style + sheet, and work much as any SGML-conformant DTP system would. + +\item Browsers will become pickier, able to offer better services at +the expense of rejecting invalid or badly broken files. Arena already +perfoms a form of consistency check on the HTML code of files, and +displays `Bad HTML' in the top corner when an offender is spotted. + +\item Users will become pickier, demanding better response from the +browser, better response from the server, and better facilities from +both. As users become more educated about the use of SGML, developers +will no longer be able to hide the deficiencies of products under the +cover of technical detail. + +\item This presupposes more user education, which is inevitable in a +developing technology. 100 years ago, motor cars appeared on the +roads, but few passengers in them understood the use of the levers and +rods which controlled them. With some minor exceptions, it is now +expected that a driver knows that turning the wheel clockwise turns +the car to the right, and {\it vice versa\/}. It will not take us that +long to perceive the innards of HTML, but it can only be done by +training and education. + +\item At some stage, investment is always needed. Many companies have +put substantial sums into the development of Internet resources, and +those that have done so with forethought and planning deserve to reap +a rich reward. It is a long-term investment, more akin to a +partnership, but support is always needed by those who undertake the +developments, especially as much of it is done in personal time and at +personal expense. + +\end{itemize} + +\noindent There is still some way to go before we achieve the ease of +use of the telephone or the radio, but the path is becoming easier +with each new development. + +\begin{thebibliography}{9} + +\bibitem{html-spec} Berners-Lee~T \& Connolly~D, {\em HyperText Markup +Language Specification~---~2.0}, Internet Draft, IETF Working Group on +HTML, December 1994. + +\bibitem{ttn41} Flynn~P, {\em Typographers' Inn}, \TeX\ and TUG NEWS, +{\bf 4}, 1, March 1995. + +\bibitem{iso-sgml} Goldfarb~C, {\em The SGML Handbook}, OUP, 1990, +ISBN 0--19--853737--9. + +\bibitem{krc} Kernighan~BW \& Ritchie~DM, {\em The C Programming +Language}, Prentice-Hall, 1978. + +\bibitem{arena-style} Lie~H {\em et al}, {\em HTML Style sheets}, +\URL|http://www.w3.org/hypertext/WWW/Style/| + +\bibitem{sgml-tools} Pepper~S, {\em The Whirlwind Guide: SGML +tools and vendors}, +\URL|ftp://ftp.ifi.uio.no/pub/SGML/SGML-Tools/SGML-Tools.txt| + +\end{thebibliography} + +\end{Article} |