Database access is described, for example, where data in a database is accessed by an inference engine. In various examples, the inference engine executes inference algorithms to access data from the database and carry out inference using the data. In examples the inference algorithms are compiled from a schema of the database which is annotated with expressions of probability distributions over data in the database. In various examples the schema of the database is modified by adding one or more latent columns or latent tables to the schema for storing data to be inferred by the inference engine. In examples the expressions are compositional so, for example, an expression annotating a column of a database table may be used as part of an expression annotating another column of the database.