TagSoup - Just Keep On Truckin'
TagSoup - Just Keep On Truckin'
This is the home page of TagSoup, a SAX-compliant parser written in Java that, instead of parsing well-formed or valid XML, parses HTML as it is found in the wild: poor, nasty and brutish, though quite often far from short. TagSoup is designed for people who have to process this stuff using some semblance of a rational application design. By providing a SAX interface, it allows standard XML tools to be applied to even the worst HTML. TagSoup also includes a command-line processor that reads HTML files and can generate either clean HTML or well-formed XML that is a close approximation to XHTML.
This is also the README file packaged with TagSoup.
TagSoup is free and Open Source software. As of version 1.2, it is licensed under the Apache License, Version 2.0, which allows proprietary re-use as well as use with GPL 3.0 or GPL 2.0-or-later projects. (If anyone needs a GPL 2.0 license for a GPL 2.0-only project, feel free to ask.)
The TagSoup logo is courtesy Ian Leslie.
TagSoup 1.2.1 is a much-delayed bug fix release. The following bugs have hopefully been repaired:
]] within a CDATA section no longer causes input to be discarded.noscript element anywhere,
the same as the script element.Download the TagSoup 1.2.1 jar
file here.
It's about 89K long.
Download the full TagSoup 1.2.1 source
here. If you don't have zip, you can use jar to unpack it.
Download the current CHANGES file here.
A company called JezUK has released Taggle, which is a straight port of TagSoup 1.2 to C++. It's a part of Arabica, a C++ XML toolkit providing SAX, DOM, XPath, and partial XSLT. I have no connection with JezUK (except apparently as source of inspiration).
The author says the code is alpha-quality now, so he'd appreciate lots of testers to shake out bugs. C++ users, go to it! Having a C++ port will be a real enhancement for TagSoup.
The code is currently in public Subversion: you can fetch it with
svn co svn://jezuk.dnsalias.net/jezuk/arabica/branches/tagsoup-port.
There are a great many changes, most of them fixes for long-standing bugs, in this release. Only the most important are listed here; for the rest, see the CHANGES file in the source distribution. Very special thanks to Jojo Dijamco, whose intensive efforts at debugging made this release a usable upgrade rather than a useless mass of undetected bugs.
As noted above, I have changed the license to Apache 2.0.
The default content model for bogons (unknown elements) is now
ANY rather than EMPTY. This is a breaking change, which I have
done only because there was so much demand for it. It can be undone
on the command line with the --emptybogons switch, or
programmatically with parser.setFeature(Parser.emptyBogonsFeature,
true).
The processing of entity references in attribute values has
finally been fixed to do what browsers do. That is, a reference
is only recognized if it is properly terminated by a semicolon;
otherwise it is treated as plain text. This means that URIs
like foo?cdown=32&cup=42 are no longer seen as
containing an instance of the ∪ character (whose name happens to
be cup).
Several new switches have been added:
--doctype-system and --doctype-public
force a DOCTYPE declaration to be output and allow setting
the system and public identifiers.
--standalone and --version allow control
of the XML declaration that is output. (Note that TagSoup's XML output
is always version 1.0, even if you use --version=1.1.)
--norootbogons causes unknown elements not to be allowed
as the document root element. Instead, they are made children of the
default root element (the html element for HTML).
The TagSoup core now supports character entities with values above U+FFFF. As a consequence, the HTML schema now supports all 2,210 standard character entities from the 2007-12-14 draft of XML Entity Definitions for Characters, except the 94 which require more than one Unicode character to represent.
startPrefixMapping and
endPrefixMapping are now being reported for all cases of
foreign elements and attributes.All bugs around newline processing on Windows should now be gone.
Since the span element is intended for fine
control of appearance using CSS, it should never have been a
restartable element. This very long-standing bug has now been
fixed.
The following non-standard elements are now at least partly
supported: bgsound, blink, canvas,
comment, listing, marquee,
nobr, rbc, rb, rp,
rtc, rt, ruby, wbr,
xmp.
In HTML output mode, boolean attributes like checked
are now output as such, rather than in XML style as
checked="checked".
Runs of < characters such as << and <<< are now handled correctly in text rather than being transformed into extremely bogus start-tags.
TagSoup is designed as a parser, not a whole application; it isn't intended to permanently clean up bad HTML, as HTML Tidy does, only to parse it on the fly. Therefore, it does not convert presentation HTML to CSS or anything similar. It does guarantee well-structured results: tags will wind up properly nested, default attributes will appear appropriately, and so on.
The semantics of TagSoup are as far as practical those of actual HTML browsers. In particular, never, never will it throw any sort of syntax error: the TagSoup motto is "Just Keep On Truckin'". But there's much, much more. For example, if the first tag is LI, it will supply the application with enclosing HTML, BODY, and UL tags. Why UL? Because that's what browsers assume in this situation. For the same reason, overlapping tags are correctly restarted whenever possible: text like:
This is <B>bold, <I>bold italic, </b>italic, </i>normal text
gets correctly rewritten as:
This is <b>bold, <i>bold italic, </i></b><i>italic, </i>normal text.
By intention, TagSoup is small and fast. It does not depend on the existence of any framework other than SAX, and should be able to work with any framework that can accept SAX parsers. In particular, XOM is known to work.
You can replace the low-level HTML scanner with one based on Sean McGrath's PYX format (very close to James Clark's ESIS format). You can also supply an AutoDetector that peeks at the incoming byte stream and guesses a character encoding for it. Otherwise, the platform default is used. If you need an autodetector of character sets, consider trying to adapt the Mozilla one; if you succeed, let me know.
I am also distributing TSaxon, a repackaging of version 6.5.5 of Michael Kay's Saxon XSLT version 1.0 implementation that includes TagSoup. TSaxon is a drop-in replacement for Saxon, and can be used to process either HTML or XML documents with XSLT stylesheets.
If you go through the TagSoup source and replace all references to
HashMap with Hashtable and recompile,
TagSoup will work fine in Java 1.1 VMs. Thanks to Thorbjørn
Vinne for this discovery.
Due to a bug in the versions of Xalan shipped with Java 5.x and 6.x, TagSoup will not build out of the box. You need to retrieve Saxon 6.5.5, which does not have the bug. Unpack the zipfile in an empty directory and copy the saxon.jar and saxon-xml-apis.jar files to $ANT_HOME/lib. The Ant build process for TagSoup will then notice that Saxon is available and use it instead.
In addition, if you are building on a Debian-derived distro, you will need to install not only the ant package but the ant-optional package as well.
It is possible to run TagSoup as a program by saying java
-jar tagsoup-1.2.1 [option ...] [file ...].
Files mentioned on the command line will be parsed individually. If no
files are specified, the standard input is read.
The following options are understood:
--fileshtml extensions changed
to xhtml. Otherwise, all output is sent to the standard output.--html--omit-xml-declaration--method=html--doctype-system=systemidDOCTYPE declaration with the specified systemid.--doctype-public=publicidDOCTYPE declaration with the specified publicid.--version=version--standalone=[yes|no]--pyx--pyxin--nons--nobogons--nodefaults--nocolons--norestart--ignorable--emptybogons--any--norootbogons--lexical--reuse--nocdatascript and style elements
to treat them as ordinary #PCDATA (text-only) elements, as in XHTML, rather than
with the special CDATA content model.--encoding=encoding--output-encoding=encoding--help--versionTagSoup supports the following SAX features in addition to the standard ones:
TagSoup supports the following SAX properties in addition to the standard ones:
TagSoup is written in the world's finest imperative programming language, as opposed to my TagSoup, which is written in perhaps the world's most widely used imperative programming language. As far as I can make out, TagSoup only lexes its input, and does not attempt to balance tags in the style of my TagSoup.
BeautifulSoup is closer to my TagSoup, but is written in Python and returns a parse tree. I believe its heuristics are hard-coded for HTML. There is a port to Ruby called RubyfulSoup.
There are a variety of other HTML SAX parsers written in Java, notably NekoHTML, JTidy (a port of the C library and tool HTML Tidy), and HTML Parser. All have their good and bad points: the general view around the Web seems to be that TagSoup is the slowest, but also the most robust and reliable.
Finally, there is a full port of my TagSoup to C++, but unfortunately it is currently trapped inside IBM. The process to release it as Open Source is under way, and I hope to feature it here some time soon.
I gave a presentation (a nocturne, so it's not on the schedule) at Extreme Markup Languages 2004 about TagSoup, updated from the one presented in 2002 at the New York City XML SIG and at XML 2002. This is the main high-level documentation about how TagSoup works. Formats: OpenDocument Powerpoint PDF.
I also had people add "evil" HTML to a large poster so that I could clean it up; View Source is probably more useful than ordinary browsing. The original instructions were:
SOUPE DE BALISES (BE EVIL)!
Ecritez une balise ouvrante (sans attributs)
ou fermante HTML ici, s.v.p.
There is a tagsoup-friends mailing list hosted at Google Groups. You can join via the Web, or by sending a blank email to tagsoup-friends-subscribe@googlegroups.com. The archives are open to all.
Online TagSoup processing for publicly accessible HTML documents is now available courtesy of Leigh Dodds.