Is the RDF model an entity-relationship mode? Yes and no. It is great as a basis for ER-modelling, but because RDF is used for other things as well, RDF is more general. RDF is a model of entities (nodes) and relationships.
This document defines an abstract syntax on which RDF is based, and which serves to link its concrete syntax to its formal semantics. This abstract syntax is quite distinct from XML's tree-based infoset [XML-INFOSET]. It also includes discussion of design goals, key concepts, datatyping, character normalization and handling of URI references.