SIGNIFICANT ECONOMIES can be achieved in distributed learning systems architected with a focus on interoperability and reuse. The key building blocks of an efficient distributed learning architecture are the use of standards and XML technologies. The goal of plug and play capability among various components of a distributed learning system requires the specification of standards for each component. Here we examine one component in distributed learning system architecture, namely, the metadata for the learning object. Metadata enables the cataloging and discovery of educational materials. Two metadata standards are LOM (Learning Object Metadata) and Dublin Core Metadata Element Set. LOM was released as IEEE 14.12.1 in June 2002. Dublin Core was ratified by the International Standards Organization (ISO) in January 2003 as ISO 15836. Interoperability of components across platforms, languages, and systems utilizes XML technologies to implement the distributed learning standards. We include an explanation of the fundamentals of XML and explore the role of XML technologies in distributed learning.