Description of the project -------------------------- This project defines **object schemas** of the OpenAIRE main entities and the relationships that intercur among them. Namely it defines the model for - the graph internal representation, defined under the package `eu.dnetlib.dhp.schema.oaf` - the scholexplorer content representation, defined under the package `eu.dnetlib.dhp.schema.sx` - the contents acquired from the metadata aggregation subsystem, defined under the package `eu.dnetlib.dhp.schema.mdstore` - the ORCID common schemas, defined under the package `eu.dnetlib.dhp.schema.orcid` Te serialization of such objects (data store files) are used to pass data between workflow nodes in the processing pipeline.