8. An apparatus, comprising: one or more processors; memory; and a program module, wherein the program module is stored in the memory and, during operation of the apparatus, is executed by the one or more processors to translate a first query into an edge query, the program module including: instructions for receiving the first query that is associated with a first type of database; instructions for translating, using primitives, the first query into the edge query that is associated with a graph database storing a graph, wherein: the first type of database has a different data model than the graph database; the graph comprises nodes, edges between the nodes, and predicates to represent and store data with index-free adjacency; and the primitives include: a rule based on edges in the graph that expresses a relational schema in the first type of database, and information associated with a compound key that specifies a relationship between the nodes, the edges and the predicates in the graph corresponding to a table in the first type of database; instructions for executing the edge query against the graph database, wherein the edge query identifies an edge associated with a predicate that specifies one or more of the nodes in the graph; and instructions for receiving a result in response to the edge query, wherein the result includes a subset of the graph.
8. An apparatus, comprising: one or more processors; memory; and a program module, wherein the program module is stored in the memory and, during operation of the apparatus, is executed by the one or more processors to translate a first query into an edge query, the program module including: instructions for receiving the first query that is associated with a first type of database; instructions for translating, using primitives, the first query into the edge query that is associated with a graph database storing a graph, wherein: the first type of database has a different data model than the graph database; the graph comprises nodes, edges between the nodes, and predicates to represent and store data with index-free adjacency; and the primitives include: a rule based on edges in the graph that expresses a relational schema in the first type of database, and information associated with a compound key that specifies a relationship between the nodes, the edges and the predicates in the graph corresponding to a table in the first type of database; instructions for executing the edge query against the graph database, wherein the edge query identifies an edge associated with a predicate that specifies one or more of the nodes in the graph; and instructions for receiving a result in response to the edge query, wherein the result includes a subset of the graph. 10. The apparatus of claim 8 , wherein the first type of database is different than a relational database.