When selecting cataloging and metadata standards, there are several factors to consider, such as the type, size, scope, audience, and goals of your library. Additionally, you need to think about the characteristics, formats, and sources of your resources, as well as the compatibility and availability of your systems and tools. Some of the most popular cataloging and metadata standards used in library services are RDA (Resource Description and Access), MARC (Machine-Readable Cataloging), Dublin Core, MODS (Metadata Object Description Schema), and METS (Metadata Encoding and Transmission Standard). RDA provides instructions for describing resources in any format or medium while MARC specifies how to encode bibliographic data in a binary format. Dublin Core defines 15 elements for describing resources in a human- and machine-readable way. MODS creates a schema for expressing bibliographic data in XML based on MARC. Finally, METS defines a schema for encoding descriptive, administrative, and structural metadata in XML for digital objects and collections.