MODS (Metadata Object Description Schema)與METS(Metadata Encoding and Transmission Standard) 是美國國會圖書館所推動的兩種標準。MODS是一套包含資料查詢、檢索、管理等多重功能在內的數位化物件描述標準，可涵蓋既有MARC21的書目記錄，同時並應用於數位資源編目。METS則是針對後設資料的編碼描述與管理架構，除可作為數位物件貯存庫與數位物件資料交換的標準機制外，亦可作為數位圖書館存取與展現所需之編碼機制。目前全球的數位化風潮已累積了大量的數位物件資料，更有效率、更具互通性的組織工具也是各界所期盼。MODS與METS已逐漸累積各界的應用經驗，對圖書館整合網路時代豐富的異質性資源開闢了一條新的路徑。

The Library of Congress, U.S.A. promotes two kinds of standards, the MODS and the METS. MODS is a metadata object description schema which includes multiple functions, such as digital object inquiring, searching, and management. METS is a metadata encoding and transmission standard for encoding descriptive, administrative, and structural metadata, regarding objects within a digital library. There have been a great amount of accumulated digital objects since the worldwide digitalization of materials. A more efficient and interoperable medium of metadata has presently been desired. In view of such a thriving development of digitalization, MODS and METS have certainly opened up a new route for the integration and interoperability of abundant and heterogeneous interlibrary resources.