編目規則中的資料類型標示 (General Materials Designations，簡稱GMD) 用來區別資料類型的名稱，規定著錄於正題名之後，對目錄使用者有提示預警的功能。線上目錄中資料類型標示的展現是否發揮預期功能，固然值得重視，而新世紀網路多媒體資料類型標示的著錄問題，尤為編目人員之關切所在。本文試從資料類型標示的相關文獻，探討其意義、源起、演變、功能、使用及問題，期與同道共勉。

In cataloging rules, a general material designation (GMD) refers to a term that indicates the class of material to which an item belongs. GMD is given after the proper title for early warning. Faced with a number of issues concerning the future of GMD, particularly in the light of new types of materials and the increasing occurrence of multi-media, the author describes its definition, origin, development, function, cataloging problems and the possible options for use in the Chinese Cataloging Rules and AACR2R.