Domain-specific language

Domain-specific language (DSL) is a type of programming language or specification language dedicated to a particular problem domain, a particular problem representation technique, and/or a particular solution technique. The concept isn't new—special-purpose programming languages and all kinds of modeling/specification languages have always existed, but the term has become more popular due to the rise of Domain-Driven Design (DDD).

Overview

A domain-specific language is created specifically to solve problems in a particular domain and is not intended to be able to solve problems outside it (although that may be possible to some extent). This is in contrast to a general-purpose language (GPL), which is designed to solve problems in any domain. The idea is that a domain-specific language should be able to express the relevant concepts and operations in a way that is more direct and less verbose than a general-purpose language would allow.

Types of DSLs

There are two main types of domain-specific languages: internal (or embedded) DSLs and external DSLs.

Internal DSLs are domain-specific languages implemented as libraries in a host general-purpose language. The host's syntax and semantics can restrict the design of internal DSLs. Examples of internal DSLs include LINQ (Language Integrated Query), a set of extensions to .NET Framework that encompass language-integrated query, set, and transform operations.

External DSLs are stand-alone languages with custom syntax and semantics. They can be implemented from scratch or by transforming the DSL program into a program in a general-purpose language. Examples of external DSLs include HTML (HyperText Markup Language), CSS (Cascading Style Sheets), and SQL (Structured Query Language).

Advantages and Disadvantages

The main advantage of domain-specific languages is that they can be more expressive in their domain than general-purpose languages. They can also be easier to learn and use, as they are tailored to a specific domain and thus use terminology and concepts familiar to users in that domain.

However, domain-specific languages also have disadvantages. They can be harder to design and implement than general-purpose languages, as they need to capture the nuances of their specific domain. They can also be less flexible and harder to extend than general-purpose languages, as they are not designed to be used outside their domain.

See also

• Programming paradigm
• Model-driven engineering
• Software language engineering