Data model introduction

A vertex defines an object such as a person, location, or recipe; think of a vertex as a noun. Each vertex has a unique identifier, and a single label that denotes the type of entity the vertex represents. Properties identify the partition keys and clustering keys to locate physical storage location, as well as additional non-primary key attributes. Two vertices are adjacent to one another if they share an edge, whereas a vertex is incident to an edge. Vertices may have one to many defined properties, with at least one partition key defined. For scale, the number of vertices can number in the billions.

An edge defines a directional binary relationship, or connection, between two vertices. A person can create software, or a person can write a book; think of edges as verbs. Each edge in DataStax Graph (DSG) has a unique identifier, and a single label that denotes the type of connection the edge represents. Multiple edges with the same direction and label can connect the same two vertices if the edge labels are created with unique clustering keys. For convenience, DSG stores each unique edge in one direction, but a special index inverse() can create opposite direction edges for any edge label. Edges may have two to many defined properties, with a partition key defined by the partition keys of the vertex labels. Edges are incident to a vertex. For scale, the number of edges can number in the billions.

A property, which consists of a property key and a property value, defines the attributes of vertices or edges Properties can have multiple values or properties of properties using CQL collections, tuples, or user-defined types (UDTs). Properties are not mandatory for vertices or edges, except for the properties that define the partition keys.