XML::DOM::Attr extends XML::DOM::Node.
The Attr nodes built by the XML::DOM::Parser always have one child node
which is a Text node containing the expanded string value (i.e. EntityReferences
are always expanded.) EntityReferences may be added when modifying or creating
a new Document.
The Attr interface represents an attribute in an Element object.
Typically the allowable values for the attribute are defined in a
document type definition.
Attr objects inherit the Node interface, but since they are not
actually child nodes of the element they describe, the DOM does not
consider them part of the document tree. Thus, the Node attributes
parentNode, previousSibling, and nextSibling have a undef value for Attr
objects. The DOM takes the view that attributes are properties of
elements rather than having a separate identity from the elements they
are associated with; this should make it more efficient to implement
such features as default attributes associated with all elements of a
given type. Furthermore, Attr nodes may not be immediate children of a
DocumentFragment. However, they can be associated with Element nodes
contained within a DocumentFragment. In short, users and implementors
of the DOM need to be aware that Attr nodes have some things in common
with other objects inheriting the Node interface, but they also are
The attributes effective value is determined as follows: if this
attribute has been explicitly assigned any value, that value is the
attributes effective value; otherwise, if there is a declaration for
this attribute, and that declaration includes a default value, then
that default value is the attributes effective value; otherwise, the
attribute does not exist on this element in the structure model until
it has been explicitly added. Note that the nodeValue attribute on the
Attr instance can also be used to retrieve the string version of the
In XML, where the value of an attribute can contain entity references,
the child nodes of the Attr node provide a representation in which
entity references are not expanded. These child nodes may be either
Text or EntityReference nodes. Because the attribute type may be
unknown, there are no tokenized attribute values.