one of the documented procedures in this installation of the ACS
tag_content   text
What it does:
Yields content tag associated with the text
Defined in: /web/philip/tcl/ad-content-tagging.tcl

Source code:

    ns_share tag_array
    set user_id [ad_get_user_id]
    util_memoize "get_content_tags" [ad_parameter CacheTimeout content-tagging]
    set text [ns_striphtml [string tolower $text]]
    # replace one or more non-alphanumerics into 
    # one space to make a Tcl list
    regsub -all {[^A-z0-9 ]+} $text " " text
    set returned_tag 0
    foreach word $text { 
	if [info exists tag_array($word)] {
	    set returned_tag [expr $tag_array($word)|$returned_tag]
    return $returned_tag