This paper presents a conceptual metadata framework intended to support the development of interoperable metadata standards and applications. The model rests on the fundamental concept of an "abstract model" for metadata, as exemplified by the DCMI Abstract Model, and is based on concepts and ideas that have developed over the years within the Dublin Core Metadata Initiative. The model thus incorporates the concepts of metadata vocabularies, schemas, formats and application profiles into a single framework that can be used to analyse and compare metadata standards, and aid in the process of harmonization of metadata standards. In this paper, the model is used to compare the Dublin Core metadata standard and the IEEE LOM standard. Some fundamental differences between the two standards are discussed briefly, and important gaps in the current set of Dublin Core metadata specifications are noted.