nxml

Overview

A new mode for editing XML documents from within GNU Emacs. It’s a milestone in that it’s the first open-source editing application to enable context-sensitive validated editing against Relax NG schemas. It also provides a clever mechanism for real-time, automatic visual identification of validity errors, along with flexible syntax-highlighting capabilities

Emacs Installation

;; Add the nxml files to emacs’s search path for loading: (setq load-path (append load-path ‘(“/usr/nxml/nxml-mode-20041004/”)))

;Automatically load nxml-mode each time I start Emacs. Note that ;rng-auto.el does not load all of the nxml-mode code; it merely sets ;things up so that all the features of nxml-mode will be autoloaded ;properly.

(load “/usr/nxml/nxml-mode-20041004/rng-auto.el”)

;Use nxml-mode automatically for files with an extension of xml, ;xsl, rng or xhtml.

(setq auto-mode-alist (cons ‘(“\.\(xml\|xsl\|rng\|xhtml\)\’” . nxml-mode) auto-mode-alist))

;completes the tag when you type ‘</’

(custom-set-variables ‘(nxml-slash-auto-complete-flag t))

Validation

Normally, as soon as emacs associates your document with a schema, nxml-mode constantly validates your document against the schema with every keystroke.

If validation is in effect and your document is not valid against the schema, the point where the document becomes invalid is shown with thin red underlining.

Schema Association

Because going DTD-less means that you can also go without DOCTYPE declarations in your documents, and because the Relax NG specification does not mandate any way for associating a document with a Relax NG, some mechanism needs to be provided at the editing application level; Emacs/nXML provides two mechanisms: one for manually specifying a Relax NG schema by browsing for it on your local filesystem, and one customizable mechanism for automatically associating a document with a schema.

The schema auto-association mechanism works by looking at the filename extension of the document (it’s configured by default to do it for .html, .xsl, .rdf, and .rnc files), or failing that, by looking at the document’s root element (for example, it’s configured by default to associate the DocBook schema with documents that have book or article root elements, the XSLT schema with documents that have stylesheet or transform root elements, etc.)

http://infohost.nmt.edu/tcc/help/pubs/nxml/ar01s05s01.html

C-c C-w Asks what schema you are using. If your document is connected with a schema, the path to the schema appears in the minibuffer. If no schema is in effect, you will get the message “Using vacuous schema”

M-x goto-char Read a number n and move point to buffer position n. Position 1 is the beginning of the buffer.

Procedure:

Create a schema location file (schemas.xml) in same the directory containing the document (test.xml). The location file looks like this:

  <?xml version="1.0"?>
  <locatingRules xmlns="http://thaiopensource.com/ns/locating-rules/1.0">
    <uri resource="test.xml" uri="test.rnc"/>
  </locatingRules>

Notice the location file contains the line:

   <uri resource="f" uri="s"/>

It means associate XML file f with schema file s.

In this example, the “test.rnc” file contains this:

  element resume { 
    element name { text },
    element address { text },
    element home-phone { text },
    element cell-phone { text },
    element email-address { text }
  }

Note: The file kept reporting errors for the longest time because I had an extra “,” at the end of the line “element email-address { text }”.

Face Customizations

change attribute names to be different, which you can do by changing these for example:

nxml-attribute-prefix-face nxml-attribute-colon-face nxml-attribute-local-name-face

Resources

Code at http://thaiopensource.com/download/

Documentation:

http://infohost.nmt.edu/tcc/help/pubs/nxml/index.html

http://www.thaiopensource.com/nxml-mode/

http://www.dpawson.co.uk/relaxng/nxml/

Problems and Futures: http://groups.yahoo.com/group/emacs-nxml-mode/

Next, tips on linking a rng schema to a document: http://www.advogato.org/person/jamesh/diary.html?start=158