This procedure is defined in the server but not documented via ad_proc or proc_doc and may be intended as a private interface.
The procedure is defined as:
proc dom::Element:GetByTagName {token name} { array set node [set $token] set result {} if {$node(node:nodeType) ne "documentFragment" } { foreach child [set $node(node:childNodes)] { unset -nocomplain childNode array set childNode [set $child] if {$childNode(node:nodeType) eq "element" && [GetField childNode(node:nodeName)] eq $name } { lappend result $child } } } elseif {[llength $node(document:documentElement)]} { # Document Element must exist and must be an element type node unset -nocomplain childNode array set childNode [set $node(document:documentElement)] if {$childNode(node:nodeName) eq $name } { set result $node(document:documentElement) } } return $result }