GUIDELINES AND CONVENTIONS ARE PRESENTED FOR THE SELECTION OF APPROPRIATE TECHNICAL SUBJECT INDEXING AND RETRIEVAL TERMINOLOGY AND THE DISPLAY OF THIS TERMINOLOGY IN A THESAURUS FORMAT. THESE CONVENTIONS WERE DEVELOPED BY PROJECT LEX, THE DOD TECHNICAL THESAURUS TASK FORCE, IN COOPERATION WITH THE ENGINEERS JOINT COUNCIL. A DISCUSSION IS GIVEN OF (1) THE CRITERIA FOR DETERMINING THE USEFULNESS OF PROSPECTIVE THESAURUS TERMS OR "DESCRIPTORS," (2) MEANS OF RESOLVING AMBIGUITIES AMONG DESCRIPTORS, AND (3) METHODS FOR SYSTEMATICALLY CREATING A CROSS REFERENCE STRUCTURE THAT WILL DISPLAY HIERARCHICAL AND CONCEPTUAL INTERRELATIONSHIPS. THE THESAURUS FORMAT WILL COMPRISE FIVE MAIN SECTIONS, (1) AN INTRODUCTORY STATEMENT EXPLAINING THE PURPOSE OF THE THESAURUS AND THE WAY IN WHICH IT IS ARRANGED, (2) AN ALPHABETICAL LISTING OF ALL DESCRIPTORS AND CROSS REFERENCES, (3) DESCRIPTORS ARRANGED BY SUBJECT CATEGORIES BASED ON THE COSATI SUBJECT CATEGORY LIST, (4) A GRAPHIC DISPLAY OF HIERARCHICAL RELATIONSHIPS, AND (5) A PERMUTED DISPLAY OF ALL DESCRIPTORS IN THE ORDER OF EACH MEANINGFUL WORD. THIS DOCUMENT IS AVAILABLE AS AD-633-279 FROM THE CLEARINGHOUSE FOR FEDERAL SCIENTIFIC AND TECHNICAL INFORMATION, SPRINGFIELD, VIRGINIA 22151, $3.00 FOR HARD COPY, $0.65 FOR MICROFICHE, 28 PAGES. (AUTHOR)