Designing and Building Domain-Specific Languages for Business Flexibility

Modern businesses must constantly navigate unprecedented challenges to quickly adapt to evolving market dynamics and customer demands. The integration of technology plays a pivotal role in enabling organizations to define and modify their business logic with unparalleled flexibility and precision. Domain-specific languages (DSLs) are instrumental tools, offering tailored solutions that cater to specific industry needs and drive sustainable growth. 

This article explores the transformative impact of DSLs in revolutionizing software solutions, empowering businesses to innovate and excel in a rapidly changing environment. 

What is a domain-specific language (DSL)?   

In this context, a “domain” represents the specific business logic of an industry or its subdomains. For example, credit cards in the finance industry, online shopping in the retail industry, voice and data in the telecom industry, etc. Whether it’s telecom services, retail transactions, or financial operations, each domain requires a tailored language that encapsulates its unique entities and actions.  

A DSL is a “programming language” designed to work with abstractions that are specific to a “domain”. The language contains structures and keywords specific to the entities and actions of the specific domain. The domain can be as wide or as narrow as the scope of the software solution being designed.  

DSLs can be applied in numerous scenarios to deliver the desired flexibility and performance:  

• Sales Commissions: Calculating incentives based on sales performance.  
• Telecom Services Rating and Billing: Determining charges for voice, data, and IPTV services.  
• Discounts and Promotions: Applying client-specific discounts and promotions.  
• Commercial Offerings: Tailoring product offerings based on client segments and transaction histories.  
• Data Filtering: Enabling users to define conditions to filter data within business processes. 

Designing and Building DSLs  

When deciding to use DSLs to provide the necessary flexibility, the first step is designing the language itself, including its syntactic and semantic characteristics. This phase requires meticulous research into the domain and use cases. It’s essential to create a language flexible enough to support all business scenarios while remaining simple enough for end users to utilize with minimal IT support.  

One significant challenge is determining the “runtime” of the DSL. Understanding user requirements is crucial for designing the language, which in turn helps in selecting the appropriate runtime. Knowing the runtime in advance can simplify the compilation and execution processes. Therefore, considering runtime alternatives during the language design phase can be a beneficial approach. 

Once the syntax and semantics are defined, the next step is to choose the runtime environment where the DSL will operate. There are several options depending on the language characteristics and scope:  

• Database Engine: If the business rules in your DSL primarily involve “filtering conditions” that include or exclude data from predefined datasets, translating the DSL into SQL fragments and executing them as a SQL query in a database engine is a practical approach. The core SQL query can be built either statically or dynamically, with user-defined rules translated into SQL conditions appended to the core SQL for execution. 
• Business Rule Engines (BRE): When the DSL’s business rules are conditional actions that may trigger further actions, BREs are a suitable option. For instance, rules like “apply a 20% discount for products over $500” or “cap discounts at 50%” are well-suited for BREs. Forward chaining BREs, such as Jboss Drools, CLIPS, Jess, and IBM ODM, are typically more appropriate for these types of rules, though backward chaining BREs like Prolog and ECLIPSe can also be used depending on the requirements.  

With the language and runtime defined, the next step is to compile or translate users’ rules into the runtime’s language. Tools like ANTLR can facilitate this process by generating lexical and syntactic analyzers from the language’s BNF specification. Additionally, implementing the “code generation” phase of the compiler, which translates the DSL into the target language (e.g., SQL, Drools), is critical for the correctness and performance of the DSL. 

Integrating the compiler and runtime into the application involves several key features: 

• Business Rules Edition UI: An intuitive interface for creating and editing business rules, with features like syntax highlighting and real-time error checking, is essential for end users. 
• Business Process Running/Scheduling: The integration point where rules are executed within the overall workflow, reading inputs, and producing outputs as part of the business process. 
• Runtime Loading: Uploading rules and data into the runtime, especially when using BREs, often requires implementing code to load information from the database. 
• Results Processing: Extracting and utilizing results generated by the DSL within the overall workflow, ensuring they are stored or passed to subsequent steps in the business process. 

Effectiveness of DSLs 

DSLs are most effective when their scope is narrowly defined. The language should be focused on specific business needs, avoiding unnecessary complexity that requires programming skills uncommon among non-programmers. Over time, repeating patterns in DSL usage may emerge, indicating that the language could have been simpler if designed for those patterns initially. For higher flexibility needs, involving developers to maintain business rules is often more practical than building a highly flexible language. In such cases, a “Domain Specific Framework” with abstractions for creating new business logic using general-purpose programming languages, coupled with modern DevOps tools and practices, can be a more appealing strategy. 

Conclusion 

Domain-specific languages are powerful tools for narrowly focused domains, providing significant business value by allowing end users to define and modify business logic. An iterative approach, expanding the language’s capabilities based on real business needs, can be highly effective. For broader flexibility, integrating a continuous integration/continuous deployment (CI/CD) approach with developers writing business logic in general-purpose programming languages may be a better solution.  

Building DSLs is a substantial effort, requiring careful design and development to achieve the desired business flexibility. So, be aware of the cost if you decide to go with DSLs.