A service interface is a component of a Visual Studio project. For these tutorials, you'll create one Visual Studio Solution to contain your native COBOL IMTK projects – one for each tutorial. You create the solution, and by inheritance the projects as well, using the Enterprise Server Application template.
Visual Studio opens the Solution Explorer for the IMTKTutorialsESA solution, showing the IMTKTutorialsESA project. Best practices dictate that each service interface should be in its own project. Therefore, you will not use the default IMTKTutorialsESA project but instead will create a separate project, within the IMTKTutorialsESA Solution, for each tutorial.