Data Integration and Form Data Models
What to know
A Form Data Model (FDM) abstracts backend data sources (REST, SOAP, OData, databases) into data model objects, properties, and services. Know the steps: create the FDM, add data sources, define entities (objects) and associations, and configure read/write services (get, create, update, delete). Understand prefill (bind form fields to FDM get services) and submit (bind to create/update services).
Integration concepts
Know how AEM Forms Data Integration uses swagger/OpenAPI definitions for REST, and how authentication (basic, OAuth, API key) is configured per data source. Understand FDM service invocation from rules and workflows, and the expression capabilities (computed fields, filters). Know prefill service configuration and how bind references map form fields to model properties.
Traps
A common trap: an FDM read service returns data but prefill fails because the form field is not bound to the correct model property. Another: submit fails because the create/update service is not enabled or the entity lacks the required association. Questions also test that OData sources expose entities differently than REST. Watch for confusion between prefill (read) and submit (write) service selection.
Rule of thumb
For every field you want prefilled, there must be a binding to an FDM property AND a get service that returns that property; for every submitted field, the write service must accept it.
Worked example
A form prefills customer name from a REST endpoint. Configure the FDM with a get-customer service, bind the name field to customer.name, and set the form's prefill service to that FDM service. If the name is blank, check the binding, not the endpoint.