Exercising the application through a presentation layer
The service-layer applications we have designed, such as the importer application, expose REST APIs for invocation by users. The most direct way for a user to exercise these applications is by sending an HTTP query. But an HTTP query, though simple to frame for a technically skilled person, may look cryptic to the laypeople who are our applications' target users. Therefore, it is common practice to mask the complexity of framing such HTTP queries through applications that provide more intuitive interfaces, which present easy-to-understand information and options to users. For example, consider the trade request we demonstrated earlier using curl. All an importer really needs to specify is the ID of the proposed trade, the description of goods, the amount, and the exporter to whom the proposal is being made. An ideal presentation application would prompt the user to enter these pieces of information, and possibly offer a...