Not every diagram defines a valid composite table. First, it must contain only bound tables, unbound and SQL-based tables are not allowed, see Bound, SQL-Based and Unbound Tables. The diagram must also satisfy the following conditions ensuring that it represents a plain table, a rowset:

• It must be a tree, that is, a connected graph without loops: every two nodes are connected with an arc path, and there are no cyclic paths in the graph.
• One-to-many arcs must not branch. In formal terms, this means that for each group of nodes that are connected with many-to-one arcs to each other (or for a single node if it does not have adjacent many-to-one arcs), there can be only one (or none) outgoing one-to-many arc.

For example, the following diagram represents a valid composite table (one-to-many relations highlighted blue; groups of nodes interconnected many-to-one filled with the same pattern):

The following three diagrams do not represent valid composite tables:

 

In the above image the diagram is not connected and consists of two independent parts.

The above image illustrates a one-to-many relations branching.

In the above image the diagram is not connected; there is no path from B to C and vice versa. To make this diagram a correct composite table, invert one of the relations.

In the above image the diagram is not connected and contains a loop.