Domain Specific LanguagesDesign Patterns and Methodologies

Lakshan Perera (lakshan@web2media.net)

Faculty of Information TechnologyUniversity of Moratuwa

  

  

“Our understanding of the nature of language and the mental processes and structures that underlies its use and acquisition”

Noam ChomskyCartesian Linguistics

  

What is Domain Specific Language(DSL) ?

  

“(DSL) is a computer language that'stargeted to a particular kind of problem,rather than a general purpose languagethat's aimed at any kind of softwareproblem.”

Martin Fowler

  

4th Generation of Programming Languages

  

Evolution

➣ APT (1957 – 1958)

➣ COBOL, FORTRAN and PERL

➣ Unix Mini-languages (yacc, lex, make)

➣ Lisp (Bottom-up design)

  

Advantages of using DSL

  

Direct Involvement of Domain Expert

  

Improved Productivity

  

Runtime Efficiency

  

Considerations

➣ Cost

➣ Language of choice

➣ Complexity of Design

➣ Scope

  

Developing a DSL

  

Domain Analysis

  

Designing DSL

➣ Piggyback

➣ Language Extension

➣ Language Specialization

  

Implementing DSL

  

Internal vs External

  

External DSL

➣ Interpreter

➣ Compiler/application generator

➣ Preprocessor

➣ Extensible compiler or preprocessor

  

Internal DSL

➣ Method Chaining

➣ Expression Builder

➣ Closures

➣ Literal Collections

➣ Object Scoping

➣ Open Classes

  

Real World Examples

  

SELECT books .title, count(*) AS AuthorsFROM booksJOIN book_authors ON books .is bn = book_authors .is bnGROUP BY books .title;

  

class Category < ActiveRecord::Base has_many :articles validates_presence_of :name validates_uniqueness_of :name def url_param self.name.downcase.gsub(/\s/,'_') endend

  

employee John Doecompensate 500 dollars for each dealclosed in the past 30 days

compensate 100 dollars for each active dealthat closed more than 365 days ago

compensate 5 percent of gros s profits ifgross profits are greater than 1,000,000dollars

compensate 3 percent of gros s profits ifgross profits are greater than 2,000,000dollars

  

Future(Everyone is a programmer)

  

Questions?