本文將依發展的時間順序介紹三種値得電子圖書館領域注意的電子 文件格式：標準通用標示語言（Standard Generalized Markup Language ;簡稱SGML)、超文件標示語言（Hypertext Markup Language;簡稱HTML) 與最新艰起的可擴展標示語言（Extensible Markup Language ;簡稱XML) ，並作簡單的比較。

This article is to introduce three formats of electronic document in order of development which deserve close attention by digital library community. They are SGML ( Standard Generalized Markup Language ) 1 HTML ( Hypertext Markup Language ) and the new XML ( Extensible Markup Language ) . A Simple comparison among the three is made to show their differences.