Any integration project or custom App has to have it's functionality discussed, documented, and agreed to. From the direction of the data feed, error handling and mapping of data between the systems of an integration project, to the desired functionality, security, and way in which an App is accessed, expectations need to be set and agreed upon.
Upon successfully defining our integration or App requirements, we dive into development. This could include anything such as writing SQL queries, creating databases and tables, using .NET code to develop a program, and everything in between. Development is typically where we create the integration or App.