Visible Group / Element tags do not appear in document
For grouping purposes it is often desirable to define elements that are part of
the definition of the structure, but the element tags do not appear as part of the
document (the element contents, i.e. the children of the element so). For example,
suppose you want to specify that two XML elements repeat like this: <a/><b/><a/><b/>. To specify
this, you create a non-visible group element that encloses
a and b, and then set the maximum Occurs value to
something greater than 1. Your element definition
would look like this:
abHolder (non-visible group, loops)
a
b
When you import an XML Schema, several types of non-visible group elements are created, including the Attributes element, which holds the XML attributes of a given XML element. Having the XML attributes grouped under a single element makes it easier to work with the structure.
This is only meaningful for representations that support the notion of tagged elements like XML and in some cases EDI.