A contract describes:
- Input table schema: Data types of the columns of the input tables.
- Arguments: Input parameters (names and data types).
- Message schema: Data types of the fields within the message.
- Output: Data types of the columns of the output table.
Your SQL-GR function provides a contract to the graph engine so that the graph engine knows what output to expect from your SQL-GR function. Contracts are discussed in more detail later in this chapter.