HTML to XHTML XML Converter
Online HTML to XHTML XML Converter
http://www.cruto.com/resources/code-generators/code-converters/html-to-xhtml.aspOffline HTML to XHTML XML Converter :
Tool of the tradeThe basic tool you can use to upgrade a site from HTML to XML is HTML Tidy. Originally developed by Dave Raggett and distributed under an open source license through the W3C Web site, HTML Tidy is now maintained by a group of volunteers at SourceForge. A Java-language version (aptly called JTidy) is also available (see
Resources). Last but not least, an API allows you to integrate HTML Tidy as a library in your applications.
HTML and XML are both markup languages derived from SGML, so they have a lot in common. Still, there are two major differences:
XML syntax is far more restrictive; most importantly, in XML you must remember to close the tags.
HTML coding often has been relatively careless, so the files are rarely trouble-free to start with.
Early Web browsers encouraged sloppiness among webmasters by being extraordinarily tolerant of errors. At the time, the goal of these browsers was to get as many people on board as possible and to encourage webmasters to publish documents. The strategy worked, and Web content grew exponentially.
Still, poor coding practices caused all kind of incompatibilities, and HTML Tidy was originally designed to address this. It rewrites HTML pages to be conformant with the latest W3C standards. In the process, it fixes many common errors such as unclosed tags.
Although HTML Tidy primarily works with HTML pages, it also supports XHTML, an XML vocabulary.
As an example, I will work with a photo gallery generated with Photoshop. You can use other HTML documents, but if you'd like to experiment with the same files I use, the gallery is also available for download in the
Resources section. Listing 1 is an excerpt from the gallery -- as you can see, it's plain HTML code.
Listing 1. index.html (an excerpt)
dscn0824.jpg
A bright, red mailbox inside the castle. It seems oddly familiar
in an historic setting.
Windsor Castle
© 2003, Benoît Marchal
|
Back to topTidying upObviously, the first step is to download and install HTML Tidy (which you'll find in
Resources). HTML Tidy is available on most platforms, including Windows, Linux, and MacOS. The default executable is a command-line tool, but GUI versions are available for Windows and MacOS.
To run HTML Tidy, open a terminal and issue the following command:
tidy -asxhtml -numeric <> index.xml
That's it! HTML Tidy immediately converts index.html into index.xml. HTML Tidy will print messages that highlight issues with the original HTML document during the conversion. In most cases, you can safely ignore these messages.
HTML Tidy runs as a filter, so it expects standard input and it prints the result to the standard output. The redirection operators (<>) allow you to work with files. By default, HTML Tidy produces a clean HTML page, but you can set two options to output XML, instead:
-asxhtml outputs XHTML documents instead of HTML.
-numeric uses character entities instead of HTML entities. For example, î is replaced with î.
XPaths and empty elements
You must be careful when processing XHTML documents with XSL. XHTML is primarily a formatting language and, unlike other XML vocabularies, it adds little structure to documents. To recover the structure, you have to analyze the document and carefully craft the appropriate XPaths. In this example, it was not immediately obvious how to separate the image title from its description: There's only a line break (
) between them. Because the line break is an empty tag, it's not enough to select it to retrieve the text! Ultimately, I used the preceding-sibling axis to load the text before the empty tag.
The difference between XHTML and HTML might sound trivial (it's only an extra "X" after all) but it is important. XHTML is a version of HTML 4.01 that has been adapted to the XML syntax. The vocabulary is unchanged (XHTML uses the familiar
, , and tags, for example), but the syntax is XML, so it merges nicely in an XML workflow.
The main differences between HTML and XHTML are:
XML elements must have opening and closing tags. HTML does not require the closing tag for many elements, such as
unless they are empty elements.
Empty elements follow the XML convention. For example, the line break is written as
instead of
.
Attribute values are always quoted (for example, instead of ).
Listing 2 is the file that HTML Tidy produces when Listing 1 is provided as input. As you can see, it is a valid XML document, and it takes surprisingly little work to produce it. Listing 2. index.xml (an excerpt)
dscn0824.jpg
A bright, red mailbox inside the castle. It seems oddly familiar in
an historic setting.
Windsor Castle
© 2003, Benoît Marchal |
What if you're not happy with the XHTML vocabulary? Read on.
Back to topFurther processingBecause XHTML documents are valid XML documents, you can insert them into an XML workflow. More specifically, you can post-process them with regular XML tools (XSL, parsers, and the like).
Indeed, I am not very happy with the XHTML vocabulary for this application. Because it's a publishing vocabulary, XHTML has very little structure, and I prefer to maintain photo galleries through the ad hoc XML vocabulary shown in Listing 3 (originally introduced in my tip,
Divide and conquer large XML documents). To illustrate an XML workflow, I have written a small XSL stylesheet (see
Listing 4) that retrieves the titles, file names, dates, and descriptions from the XHTML document. The stylesheet generates a more structured version of the document that is easier to work with.
Listing 3. index-transform.xml (an excerpt)
Journey to Windsor
Windsor Castle
July 2003
dscn0824.jpg
A bright, red mailbox inside the castle.
It seems oddly familiar in an historic setting.
Listing 4. cleanup.xsl
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