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API modeling is the design and creation of APIs to ensure effective communication between different systems. Learn more, plus how OpenLegacy can help.


API Modeling: Understanding API Model Approaches

Posted by Angela Davis on June 4, 2024
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At some point, most developers and digital designers will have to consider how to create and adapt APIs for modern digital architecture

Whether you’re creating an entirely new setup or modernizing a legacy system, your tech will likely rely on APIs to deliver the desired outcomes. And, as digital architecture becomes more complex, you’re likely to need more complicated and sophisticated API designs.

API modeling can ensure the architecture you arrive at isn’t just fit for purpose but also as simple to use and efficient to create as possible. It helps designers understand exactly what they're making and who they’re making it for. It also identifies and eliminates potential issues before development starts.

Here, we’ll take you through what API modeling is, the top approaches to model APIs, and how you can successfully model your own.

What is API modeling?

Example of the RESTful approach to API modeling. 

Image source

Answering the question of “what is an API model” starts with understanding APIs, themselves. 

Application programming interfaces (APIs) are integral to modern software systems. They transfer data from one part of a digital system/application to another. They’re how apps and services communicate internally, and this communication is how things get done. 

API modeling is the process of working out how to design API systems for the best results. Put very simply, it breaks down the elements of a design into clearly defined elements and stages. This helps designers see exactly what they’re working with and why they’re doing it. 

When API modeling, you’ll do things like create data models, define call/response formats, consider authentication mechanisms, and generally put together a strategic blueprint containing all the elements necessary for a good API. 

This puts the API design process into perspective and gives designers a good understanding of every element of their application programming interface before they start building.

API model example approaches: Bottom-up and top-down

There are two major approaches to API modeling: bottom-up and top-down.

Bottom-up modeling begins with the foundational structure—the database and code framework, for instance. As it starts with the database and code structure, you may also hear this approach referred to as ‘“code-first” modeling. 

Having established and defined the code and data at the “bottom” of the system, your modeling strategy will then build the API architecture on top of this foundation. 

A bottom-up approach will usually put most of its focus on the data and code involved in your API design. This is great for eliminating problems like data redundancy, but it doesn’t always align the finished product with the needs of end users.

Top-down API modeling is a more modern approach, which makes it useful for designing more complex and sophisticated architecture. A top-down approach starts by defining the API and then maps it to the data you have. The model, therefore, must be well-defined, regardless of the underlying data. 

The top-down approach to API modeling is simultaneously more holistic and strategic than the bottom-up approach. It seeks to put the API into context by focusing on the needs of all potential users and considering how the API will be used. 

It then takes those needs and uses them strategically to design API processes and architecture, before mapping these onto the source code.

Benefits of a top-down API model approach

As APIs and API-reliant systems become more complicated and sophisticated, modeling requires an approach that allows designers to focus on the API architecture in detail. 

While bottom-up modeling can provide this to an extent, it’s more focused on the data foundation and what it can support than on the application programming interface itself.

A top-down approach, on the other hand, starts with the API, meaning the designer can dive straight into the important questions. Questions such as what will the API be used for, who’ll be using it, and what’s needed to make it as efficient and user-friendly as possible?

While bottom-up modeling does have some advantages, it’s very focused on data and code and doesn’t leave much scope for considering user needs. A top-down approach, however, puts the user first and adjusts the architecture to accommodate user needs. 

All in all, there are a lot of benefits to top-down API modeling, including:

  • Greater flexibility in API design
  • A user-focused approach, which usually leads to better user experiences
  • Its suitability for no-code solutions
  • Greater consistency in design throughout the API structure
  • Much more streamlined API communication.

A step-by-step guide to the API modeling process

So, how do you create API models? Here’s a step-by-step guide to the process:

Identify who will be using your API

The term for the end user of an API varies widely. You may hear them called actors, participants, users, and more. However you refer to them, it’s important to start your API modeling by identifying them as closely as possible.

Remember, your API is likely to be used by developers as well as consumers, so you need to understand the needs of both to create the most effective API.

Think about exactly who your users are and what they’ll be using your API for. Differentiate between different user groups as closely as possible (for example, rather than just defining “developers” as a user group, distinguish between internal developers, operations engineers, and so on). 

Determine the outcomes your API should make possible

A visual representation of how APIs can work with an example of outcomes your API modeling needs to consider.

Image source

What a user most wants from an API is for it to fulfill its purpose in the quickest, smoothest, and most efficient way possible. To build your API so it does this, you need to know your users’ desired outcomes.

For example, they might want a payment gateway API to:

  • Quickly transfer money with minimal hassle
  • Authenticate transactions
  • Run security checks.

Understanding these desired outcomes will help you design an API that’s not only secure but also quick and easy to use.

Map out the steps toward these outcomes

Having established the outcomes your API should make possible, you need to map out exactly how it’s going to achieve them.

Usually, an API will achieve its aims through a series of steps powered by API endpoints. Your job at this stage is to define these steps in sequence. For example, a payment API may use the following:

  1. Create payment request
  2. Authenticate user
  3. Authorize transaction
  4. Get bank verification
  5. Respond to authorization/verification
  6. Complete transaction
  7. Report on completed transaction

Understanding and mapping the steps your API must take to achieve desired outcomes will help you create a smoother and more streamlined process. Ultimately, this will lead to a better user experience.

Define your API model

One of the advantages of top-down modeling is that it allows your API to take shape as you map out its purposes and processes, rather than trying to cram those purposes and processes into a predefined shape. 

By this stage in a top-down model, you should have an idea of what your API will need to do and how it will do it, so you can start to define your API model.

Your final API will be made up of actions and resources. To define your API model, group the most vital actions and resources that you’ll need for your final design under relevant headings. 

For example, a payment API may group actions under headings like “authentication”, “verification”, “transfer”, and so on.

This step will give you a clearer picture of the resources your API needs and the shape it will take.

Validate the API model and ensure it’s fit for purpose

Having identified who’s using your API, what they’re using it for, how it can best fulfill its purposes, and the resources and actions it will need to do this, it’s time to validate your model.

Validation of API models can be managed using wireframes, test cases, user stories, and so on. The important thing is that you’re able to test your model against all known requirements. So, your validation techniques need to ensure that your API meets all known user needs and can do so quickly and efficiently.

As you’re testing, think about any elements that may be missing. For example, you may realize during validation that your API has a potential user base that you’ve overlooked or that it has dependencies that could cause issues. 

If these sorts of things do come up as you validate your API, this is a good thing. It means your modeling is doing its job and highlighting potential problems or overlooked aspects before the design stage begins.

Modernize legacy systems more easily with APIzation from OpenLegacy

Modeling is a crucial step in API creation. It effectively strategizes your design, giving your team a greater understanding of what they’re creating, who they’re creating it for, and how it can achieve its outcomes most effectively.

You can improve your API processes even further with APIzation from OpenLegacy. OpenLegacy makes creation, testing, and deployment fast, simple, and efficient. Our automated processes eliminate human error and overcome difficult modernization challenges with ease.

OpenLegacy really comes into its own with legacy systems. As technology evolves, it’s becoming harder and harder to make best use of these in concert with digital-native applications. At the same time, they often contain a huge amount of important data and resources, so simply scrapping them and starting again isn’t always an option.

With OpenLegacy’s API-based modernization, you can sync your legacy tech with a modern cloud system, making access to and use of your legacy systems much easier without having to go through a tortuous data transfer process. What’s more, it means you don’t need legacy backend expertise to make it happen. 

To learn more about how OpenLegacy can help with API design and system modernization, take a product tour today.

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