[Summary] Big hierarchy of XML Schema documents ... which XMLSchema vali

["Costello, Roger L." <costello@mitre.org>]

Hi Folks,

Thanks to Michael Glavassevich, Michael Kay, and Boris Kolpackov for your excellent inputs.

Here's what I learned (please correct any errors):

Suppose that your XML Schema imports/includes some XML Schemas, and they import/include some XML Schemas, and so on. Thus, there is a big hierarchy of XML Schema documents.

When does a validator read the XML Schema documents? Here are two ways that XML Schema validators could be implemented:

1. Just-in-time loading (a.k.a. on-demand loading): the validator reads an XML Schema document during instance validation, when a component from the relevant namespace is first encountered.

2. Eager loading: all XML Schema documents are (recursively) read prior to validating the XML instance document.

The following XML Schema validators all use eager loading:

    SAXON (Java)

    SAXON (.NET)

    XERCES (Java)

    XERCES (C++)

    XERCES (Perl)

    LIBXML (Gnome's libxml2)

    MSXML

    XSV


/Roger