UMLet also allows users to create their own custom UML elements. Elements can also be modified inside their palettes and immediately used as new templates this way, users can easily tailor UMLet to their modeling needs.

Learning about the various element features is supported by prototypically using them from sample palettes. UML elements are modified using text input and a small markdown dialect instead of pop-up dialogs. There are more things you can use sequence diagrams for and more advanced building blocks that we did not cover such as asynchronous requests, recursion, loops, etc.įor those looking for a hands-on activity to do, consider creating a sequence diagram for the business logic behind POST coupon/purchase in the customer loyalty app.UMLet is a UML tool aimed at providing a fast way of creating UML sketches. The example we used today was a simple use case meant to serve as an introduction to this concept. Sequence diagrams can be used to design, analyze, and understand different workflows and system integrations. In both cases, the mobile app can handle the response and display the appropriate message to the customer. However, if the response has an error, then it will follow the error route. If the response is successful, then it will follow the success route. This is represented with HTTP status code followed by the error description. We’ve already covered success so let’s take a look at the error responses. We’ve added two additional boxes to highlight the different request-response scenarios for success and error. Let’s see how error handling might look like in our sequence diagram using an alternative flow. It’s up to the receiver to listen to the request, process it, and deliver an appropriate response. The caller doesn’t care how the job gets done as long as it gets done. The majority of the work is done inside the customer loyalty app, which is abstracted into one API call. If any of these validations fail, then the API will return an error that the caller or the system making the request can handle. However, what happens if there was an issue during purchase such as insufficient points or coupon stock? How might we handle these scenarios?įortunately POST coupon/purchase has internal validations in place that checks to see if the customer and coupon exists, how many coupons are remaining, and whether or not the customer has enough points to purchase it. This is a happy case where the customer has enough points to purchase a coupon that is still in supply so the result is a new offer in their digital wallet. Customer Loyalty App returns success to Middleware 5. Middleware sends POST coupon/purchase to Customer Loyalty 4. The mobile app is the customer touchpoint, the middleware is a software commonly used for API orchestration, and the customer loyalty app is the new platform that we’re integrating with.įor the customer loyalty app, we have the following API for purchasing coupon: POST coupon/purchase (required: customer_id, coupon_id)Ĭustomer_id and coupon_id are required since the customer loyalty app needs to know who is purchasing what coupon. For this sample scenario, we will reference the following systems Let’s explore this use case with a sequence diagram. However, for the purposes of this article, let’s zoom in on step 4) buy coupon with points. Buy coupon with pointsĪs simple as it may seem, there’s actually a lot happening behind the scenes and each step can have its own sequence diagram. Referring back to our use case of mobile app customers buying coupon with points, let’s write down the typical flow for what this activity might look like from start to finish. That’s it! Of course we can add more dimensions to it, but let’s keep it simple for now. The basic building blocks for creating sequence diagrams consists of words, arrows, and system objects.

Draw.io sequence diagram