As used in sections two to eight, inclusive, the following words shall, unless the context clearly requires otherwise, have the following meanings:
''Central register'', identifying data file of missing children.
''Department'', the department of criminal justice information services.
''Director'', the commissioner of the department of criminal justice information services.
''Law enforcement authority'', any police department in the commonwealth or any of its political subdivisions.
''Missing child or children'', any person under the age of eighteen years missing from his normal and ordinary place of residence and whose whereabouts cannot be determined by the person responsible for such child's care.