The present invention relates to a method for constructing a database schema model by a user by means of a computer, comprising the steps of: providing a set of collections and/or optionally one or more relationships linking at least two of said set of collections; editing one or more of said set of collections, each of which associated with a schema definition displayed by a single table on an entity relationship diagram on a graphical interface on said computer and comprising at least one object and/or one field, said schema definition editable via a tree diagram on said graphical user interface on said computer; automatically generating by means of said computer said database schema model for a database system or a REST API; characterized in that, said set of collections comprises at least one collection comprising a nested object editable via said tree diagram with two levels or more.