We propose here a data model that generalizes the relational, hierarchical, and network models. A database scheme in this model is a directed graph, where leaves represent data and internal nodes represent connections between the data. Instances are constructed from r-values, which constitute the data space, and l-values, which constitute the address space. We define a logic for the model, and describe a non-procedural quary language that is based on the logic. Finally, we describe an algebraic query language and show that it is equivalent to the logical language.