MARC 21

英美編目規則(AACR)出版迄今已有40年的歷史，因應電子期刊、網站和電子資料庫等新興資料類型蓬勃發展，以及線上編目和編目資源分享之環境，遂而修訂英美編目規則。英美編目規則第二版2002修訂版主要修訂PartⅠ著錄第十二章，並改章名為連續性資源，至於Part Ⅱ檢索款目選擇、標目、參照部分則修訂不多。而此修訂連帶促使機讀編目格式連續性資源相關欄位之增改，主要修訂有定長欄Leader 07 Bibl Level、部分008欄以及變長欄260欄三部分。

AACR has been published and implemented in the past 40 years. Due to rapid development of new carriers like electronic journals, websites, databases, and online cataloging and shared cataloging environment, AACR has undergone revisions. This major revision of AACR2(2002) is see in Chapter 12, PartⅠ, with chapter title changed to Continuing Resources. For Part Ⅱ, little change has been made for, choice of entry, heading, and reference. As to the major related changes of MARC21, they are Leader 07 Bibl Level, partial 008 field and 260 field.