XML

XML, or eXtensible Markup Language, is a data format.

Resources edit

xml.org

Reading edit

Programming XML and Web services in TCL, Part 1 : An initial primer, Cameron Laird, 2001-04-01: surveys the state-of-the-art as of spring 2001, mainly from a Zveno-biased perspective. One deficiency of that article is its neglect of Jochen Loewer's tDOM work.
Untaught XML Schema, Cameron Laird, 2009-06-05
Microsoft patents XML word processing documents, Rupert Goodwins, 2009-08-07: Amusingly enough, Microsoft has also in August 2009 been ordered to stop selling their Word product because of its XML functionality: Injunction on Microsoft Word unlikely to halt sales, Nancy Gohring, 2009-08-11.

Examples edit

Simple XML report writer
XML Graph to canvas

Description edit

XML is a simplified form of SGML, but stricter (more regular) in some aspects:

Singleton elements must end with />
attribute values must be quoted

Example:

<father name="Jack" att1="1">
    <child name="Tom" born="1997" />
</father>

Tcl's excellent Unicode abilities make it a good language for processing XML.

Parsing edit

tDOM and TclXML/TclDOM are the two main Tcl extensions for parsing XML, providing both SAX parsing for stream-oriented parsing, and DOM for document-oriented parsing.

Validation edit

One way of specifying the valid tag structure of a class of documents is to use a Document Type Definition, DTD for short. This way was inherited from SGML. There are alternative ways ... XMLSchema, Relax(NG), ...

Generating edit

See Also:

Formatting ls information in XML: an example of a manual approach to generating XML
Minimalist XML Generation
Howto export Microsoft Outlook contacts to XML using tcom and tDom
Migrating MS Access to other databases using XML

In a mailing list conversation [reference?], Steve Ball succinctly advised, "When creating XML, I generally use TclDOM. Create a DOM tree in memory, and then use 'dom::DOMImplementation serialize $doc' to generate the XML. The TclDOM package will make sure that the generated XML is well-formed.

Alternatively, XML is just text so there's no reason why you can't just create the string directly. Eg:

puts <document>$content</document>

The problem with this is that (a) you have to worry about the XML syntax nitty-gritty and (b) the content variable may contain special characters which you have to deal with.

There are also some generation packages available, like the 'html' package in tcllib (this will be added to TclXML RSN, when my workload permits)."

DKF: If you're going for the cheap-hack method of XML generation mentioned above, you'll want this:

proc asXML {content {tag document}} {
    set XML_MAP {
        < &lt;
        > &gt;
        & &amp;
        \" &quot;
        ' &apos;
    }
    return <$tag>[string map $XML_MAP $content]</$tag>
}

Naturally, the XML_MAP variable is factorisable...

MHo: Why not using html::quoteFormValue for this purpose?

For generation of XML (HTML) the pure Tcl way, have a look at the xmlgen module of TclXML

DKF: That's when you're moving away from cheap hacks. And HTML has a lot more entities than XML, though most are optional.

If you want to get particular about entity encoding arbitrary text, this is working for me:

variable entityMap [list & &amp\; < &lt\; > &gt\; \" &quot\;\
       \u0000

Browsing / Editing edit

a little XML browser
XML DOM Tk Text Browser Editor
FanXE

Publishing edit

Anastasia: Designed for the publication of large, highly-complex XML documents and document xcollections.
xml2html: Tcl-based tool for authoring web sites in XML then rendering to HTML.

Related Technologies edit

There are a whole host of technologies related to XML:

XPath: for selecting nodes from a document
XQuery
XSL/XSLT: for transforming documents
DTD and XMLSchema: for specifying document schemas

tDOM and TclXML both provide good support for at least XPath and XSLT.

XML Formats edit

XML by itself is just a partially-standardized syntax for data. It's used as the basis for a variety of different applications, such as:

CML: Chemical Markup Language
excel xml for Excel
(X)HTML for web pages
RDF and OWL for general relational/logical data models
DocBook for technical documentation: along with other office document formats (e.g. Microsoft's office XML format, excel xml, OpenDoc, etc)
MathML
OpenMath
SOAP and XML-RPC: for remote procedure calls/web-services.
VML: Vector Markup Language, for vector graphics
XLink: a common notation for links in XML to other resources
Various configuration file formats (especially in the Java world)