The National Diet Library, Japan (NDL), with support by Xenon Limited Partners, has designed a new metadata schema based on the RDF model while developing a national platform for metadata aggregation and sharing, "Japan Search". Japan Search collects metadata from libraries, museums, archives, and research institutions across the country, and provides an integrated search service as well as APIs (SPARQL Endpoint and REST-API). The aim of this paper is to introduce the new schema, highlighting its dual-layered data model and the normalization of temporal (When), spatial (Where), and agential (Who) information provided in the source data.