Representing and organizing information in libraries has a long tradition of using rules and standards. As the very first standard encoding format for bibliographic data in libraries, MAchine Readable Cataloging (MARC) format is being joined by a large number of new formats since the late 1980s. The new formats, mostly SGML/HTML based, are actively taking a role in representing and organizing networked information resources. This article briefly describes the historical connection between MARC and the newer formats for representing information and the current development in XML applications that will benefit information/knowledge management in the new environment.