Case Studies of Successful Declarative Software Projects

Are you tired of writing imperative code that is hard to maintain? Do you wish there was a better way to express your intentions to the computer? If so, you're not alone! Many developers have discovered the power of declarative programming languages and the benefits they bring to software development. In this article, we'll be exploring some case studies of successful declarative software projects to give you an idea of what's possible with this approach.

What is Declarative Programming?

Before we dive into the case studies, let's first define what we mean by declarative programming. In contrast to imperative programming, where the programmer specifies a series of instructions for the computer to execute, declarative programming specifies the desired outcome or result without specifying the steps needed to achieve that outcome. The idea is that the language or framework takes care of the implementation details behind the scenes, leaving the programmer to focus on the problem at hand rather than the nitty-gritty of how to solve it.

Declarative programming can take many forms, from declarative languages like SQL for querying databases, to declarative frameworks like React for building user interfaces. By using such tools, developers can write cleaner, more concise, and more maintainable code that is easier to reason about.

Case Study: Ansible

Ansible is a popular open-source automation tool that is used to provision and configure servers, deploy applications, and manage infrastructure. Ansible is written in the Python programming language and uses a declarative language called YAML (short for "YAML Ain't Markup Language") to specify the desired configuration state of the target systems.

One of the most significant benefits of using Ansible is that it allows you to define your infrastructure as code, which means that you can version control your infrastructure just like you would any other codebase. This approach helps to improve collaboration, consistency, and repeatability, and also reduces the risk of manual errors that can arise when configuring systems manually.

Another benefit of Ansible is that it is agentless, meaning that you don't need to install any software on the target systems. Instead, Ansible runs "playbooks" that define the desired state of the system, and then uses SSH to execute the necessary commands to bring the system into that state.

Case Study: Terraform

Terraform is another popular automation tool that is used for managing infrastructure, but with a slightly different focus than Ansible. Terraform is concerned with the provisioning and configuration of cloud resources, such as virtual machines, storage accounts, and networking components. Like Ansible, Terraform uses a declarative language, this time called HashiCorp Configuration Language (HCL), to specify the desired state of the infrastructure.

One of the most significant benefits of using Terraform is that it supports multiple cloud platforms, including AWS, Azure, and Google Cloud Platform. This means that you can use the same tooling and language to manage your infrastructure, regardless of which cloud provider you use.

Terraform also has a strong focus on modularity, meaning that you can define reusable modules that encapsulate common patterns and configurations. This approach helps to reduce duplication and ensures that your infrastructure is consistent across multiple environments.

Case Study: Datomic

Datomic is a modern database that is designed to support the needs of modern applications. Datomic aims to address some of the challenges of traditional databases, such as data silos, rigid schemas, and heavyweight transactions.

One of the key features of Datomic is that it uses a declarative query language called Datalog to express queries over the data. Datalog is a powerful and expressive language that allows you to reason about data in much the same way as you would with a programming language. Datalog queries are also composable, meaning that you can write small, reusable queries that can be combined together to build more complex queries.

Another benefit of Datomic is that it is a "time-based" database, meaning that it stores a complete history of all changes to the data. This approach allows you to query the database at any point in time, making it ideal for auditing and tracking changes to the data.

Case Study: Nix

Nix is an open-source package manager and deployment tool that is used primarily in the Linux ecosystem. Nix is built on a unique approach to package management, in which packages are defined declaratively as sets of inputs and outputs.

The Nix language is a functional language that is used to describe the configuration of the system, including the package dependencies and the configuration files. By using a functional language, developers can take advantage of the advanced features such as immutable infrastructure, which reduces the risk of configuration drift.

Another feature of Nix is that it provides atomic rollbacks, meaning that you can easily roll back changes to the system in the event of an error or failure. This approach helps to reduce the risk of downtime, data loss, or other adverse impacts.


In this article, we've explored some case studies of successful declarative software projects across a range of domains, including infrastructure automation, database management, and package management. By adopting a declarative approach to programming, developers can reduce the complexity and cognitive load of their code and focus on expressing their intentions rather than the implementation details.

If you're interested in declarative programming, be sure to check out our website,, where we share tips, tutorials, and best practices for declarative programming languages, declarative software, and reconciled deployment or generation. With the right tools and techniques, you too can unlock the power of declarative programming and take your software development to the next level.

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Written by AI researcher, Haskell Ruska, PhD ( Scientific Journal of AI 2023, Peer Reviewed