question: private void processNode ( CAS cas , Node node , StringBuilder documentText ) { if ( node . hasChildNodes ( ) ) { if ( docIdTag != null ) { ensureIdValidity ( node ) ; } NodeList docFields = node . getChildNodes ( ) ; for ( int i = 0 ; i < docFields . getLength ( ) ; i ++ ) { Node field = docFields . item ( i ) ; int begin = documentText . length ( ) ; String nodeTag = field . getLocalName ( ) ; if ( nodeTag != null && isIncluded ( nodeTag ) ) { String nodeText = field . getTextContent ( ) ; documentText = documentText . append ( nodeText ) ; int end = documentText . length ( ) ; documentText = documentText . append ( "\n" ) ; if ( useSubstitution && substitution . containsKey ( nodeTag ) ) { nodeTag = substitution . get ( nodeTag ) ; } createFieldAnnotation ( cas , nodeTag , begin , end ) ; } } } }
target:  Add the text in current node to document text buffer, create and add to index a Field annotation out of the text. This usually processes a document.