XML

XML = Extensible Markup Language

HTML minus the formatting information. Designed to convey information rather than layout.

Example:

    <?xml version="1.0"?>
    <ADDRESS>
        <NAME>Dave Brankin</NAME>
        <LINE1>10 Somewhere Road</LINE1>
        <TOWN>Somewhere</TOWN>
        <POSTCODE>AB1 1AB</POSTCODE>
    </ADDRESS>

Well-formed XML

Note: "Well-formed XML" is a term, not a description!

Start and End tags should be nested to the same level (i.e. closed in the reverse order they were opened, this was not always necessary in HTML).
Has one root element and all other tags (excluding the xml version tag) appear within this element
A parent tag never appears within a child tag, for example the following is NOT well-formed XML:
    ....
    <TAG1>
        <TAG2>Hello Word</TAG2>
        <TAG1>                                            <--- Naughty!
            <TAG2>Hello Island</TAG2>
    ...

Using XML with IE

XML can be processed within IE using an ActiveX object:

    var myXMLDoc = new ActiveXObject("Microsoft.XMLDOM")
    myXMLDoc.async=false                <--- controls whether entire file has to be read before processing starts
    myXMLDoc.load("myfile.xml")
    var rootElement = cmlDox.documentElement
    mySpan.innerText = rootElement.childNodes.item(0).text

I'm not going into further details as (a) I think we're unlikely to use this client-side approach with the .NET infrastructure and (b) I think ActiveX in browsers may be a bit of a no-no for some clients.

Data Islands

XML incorporated within a HTML document is referred to as a "data island". Basically, just encase the XML in the <XML> tag. The ID attribute of the <XML> tag is used to give us the required "hook" into the data. For example:

<HTML>
...
<XML ID="dave">
    <PERSON>
        <FORENAME>Dave</FORENAME>
        <SURNAME>Brankin</SURNAME>
    </PERSON>
</XML>
....
    var xml=dave
    var root = xml.documentElement
    mySpan.innerText=root.childNodes.item(0).text
...

Note: No ActiveX component! ?? So why did we need one earlier? ?? The "var xml=dave" line performs the equivalent operation.

Note: The <XML> tag also supports the SRC attribute which allows an external XML file to be specified.