}\\\smash{

}}") - xsized w, - center topboundary p shifted (0,-12mm)) withcolor \MPcolor{lightorange} ; % 0.45[white,orange] ; - draw anchored.bot( - textext("\ssbf\setupinterlinespace[line=2.2ex]\framed[frame=off,align=middle]{exporting\\xml and epub\\from context}") - xsized w, - center bottomboundary p shifted (0,4mm)) withcolor \MPcolor {lesswhite} ; % 0.90white ; -) ; - -setbounds currentpicture to p ; - -\stopMPpage - -\startsection[title=Introduction] - -There is a pretty long tradition of typesetting math with \TEX\ and it looks like -this program will dominate for many more years. Even if we move to the web, the -simple fact that support for \MATHML\ in some browsers is suboptimal will drive -those who want a quality document to use \PDF\ instead. - -I'm writing this in 2014, at a time when \XML\ is widespread. The idea of \XML\ is -that you code your data in a very structured way, so that it can be manipulated and -(if needed) validated. Text has always been a target for \XML\ which is a follow|-|up -to \SGML\ that was in use by publishers. Because \HTML\ is less structured (and also -quite tolerant with respect to end tags) we prefer to use \XHTML\ but unfortunately -support for that is less widespread. - -Interestingly, documents are probably among the more complex targets of the -\XML\ format. The reason is that unless the author restricts him|/|herself or -gets restricted by the publisher, tag abuse can happen. At \PRAGMA\ we mostly -deal with education|-|related \XML\ and it's not always easy to come up with -something that suits the specific needs of the educational concept behind a -school method. Even if we start out nice and clean, eventually we end up with a -polluted source, often with additional structure needed to satisfy the tools used -for conversion. - -We have been supporting \XML\ from the day it showed up and most of our projects -involve \XML\ in one way or the other. That doesn't mean that we don't use \TEX\ -for coding documents. This manual is for instance a regular \TEX\ document. In -many ways a structured \TEX\ document is much more convenient to edit, especially -if one wants to add a personal touch and do some local page make|-|up. On the other hand, -diverting from standard structure commands makes the document less suitable for -output other than \PDF. There is simply no final solution for coding a document, -it's mostly a matter of taste. - -So we have a dilemma: if we want to have multiple output, frozen \PDF\ as well as -less-controlled \HTML\ output, we can best code in \XML, but when we want to code -comfortably we'd like to use \TEX. There are other ways, like Markdown, that can -be converted to intermediate formats like \TEX, but that is only suitable for -simple documents: the more advanced documents get, the more one has to escape -from the boundaries of (any) document encoding, and then often \TEX\ is not a bad -choice. There is a good reason why \TEX\ survived for so long. - -It is for this reason that in \CONTEXT\ \MKIV\ we can export the content in a -reasonable structured way to \XML. Of course we assume a structured document. It -started out as an experiment because it was relatively easy to implement, and it -is now an integral component. - -\stopsection - -\startsection[title=The output] - -The regular output is an \XML\ file but as we have some more related data it gets -organized in a tree. We also export a few variants. An example is given below: - -\starttyping -./test-export -./test-export/images -./test-export/images/... -./test-export/styles -./test-export/styles/test-defaults.css -./test-export/styles/test-images.css -./test-export/styles/test-styles.css -./test-export/styles/test-templates.css -./test-export/test-raw.xml -./test-export/test-raw.lua -./test-export/test-tag.xhtml -./test-export/test-div.xhtml -\stoptyping - -Say that we have this input: - -\starttyping -\setupbackend - [export=yes] - -\starttext - \startsection[title=First] - \startitemize - \startitem one \stopitem - \startitem two \stopitem - \stopitemize - \stopsection -\stoptext -\stoptyping - -The main export ends up in the \type {test-raw.xml} export file and looks like -the following (we leave out the preamble and style references): - -\starttyping - -

- 1 - First - - - - • - one - - - • - two - - - -

- -\stoptyping - -This file refers to the stylesheets and therefore renders quite well in a browser -like Firefox that can handle \XHTML\ with arbitrary tags. - -The \type {detail} attribute tells us what instance of the element is used. -Normally the \type {chain} attribute is the same but it can have more values. -For instance, if we have: - -\starttyping -\definefloat[graphic][graphics][figure] - -..... - -\startplacefigure[title=First] - \externalfigure[cow.pdf] -\stopplacefigure - -..... - -\startplacegraphic[title=Second] - \externalfigure[cow.pdf] -\stopplacegraphic -\stoptyping - -we get this: - -\starttyping - - ... - ... - - - ... - ... - -\stoptyping - -This makes it possible to style specific categories of floats by using a -(combination of) \type {detail} and|/|or \type {chain} as filters. - -The body of the \type {test-tag.xhtml} file looks similar but it is slightly more -tuned for viewing. For instance, hyperlinks are converted to a way that \CSS\ and -browsers like more. Keep in mind that the raw file can be the base for conversion -to other formats, so that one stays closest to the original structure. - -The \type {test-div.xhtml} file is even more tuned for viewing in browsers as it -completely does away with specific tags. We explicitly don't map onto native -\HTML\ elements because that would make everything look messy and horrible, if only -because there seldom is a relation between those elements and the original. One -can always transform one of the export formats to pure \HTML\ tags if needed. - -\starttyping - -

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