Domain Specific Languages

Domain Specific Language Dr. Weerasak Witthawaskul “ Mr. SweetCorn” (weerasak@hotmail.com) Narisa.com’s NJUG Meeting #3 22 July 2007

Who am I?

oop guy (Pantip)

SweetCorn (narisa.com)

Wee (weerasak.com)

UIUC – Home of Illiac, Transistor, Superconductivity, Mosaic, Paypal, YouTube, Design Patterns, Refactoring

Motorola Labs, Schuamburg IL

ThoughtWorks Inc., Chicago IL

Graduate Life

Programming Paradigm Shifts

Domain Specific Languages

Generative Programming

Model Driven Architecture (MDA) - OMG

Intentional Programming – Charles Simonyi, ex-Microsoft

Language Oriented Programming – Sergey Dmitriev, JetBrains (Home of IntelliJ IDEA)

Software Factories – Jack Greenfield, Microsoft

What is DSL?

“ วันนี้มีประชุมนริสาดอทคอม ”

ภาษาไทย

“ ทำตัวติสตดีนักถูกแมวีนมายังทำตัวชิวชิวอยู่อีก ...”

ภาษาไทยเด็กแนว (domain specific)

What is DSL?

Mini-language to solve specific “domain” problem

Why is it important?

SQL – Relational Database Manipulation Language

Domain specific vs General purpose

What constitutes “domain specific” in programming languages?

Mini Game

“ What languages are they?”

Are they languages for specific domains?

From http://www.ntecs.de/old-hp/uu9r/lang/html/lang.en.html

What Languages are they?

#include <stdio.h>

main() {

printf("Hello World ");

}

C

.MODEL tiny

.CODE

ORG 100h

HELLO PROC

MOV AH,09h

LEA DX,msg

INT 21h ;Display Hello World

MOV AX,4C00h ;Exit to DOS

INT 21h

HELLO ENDP

msg DB 'Hello World$'

END HELLO

Assembly Language Intel 80x86 (DOS/MASM)

<?php

echo "Hello World ";

?>

PHP

public class HelloWorld {

public static void main(String[] args)

System.out.println("Hello World");

}

}

Java

How about JME? JEE?

PROGRAM HelloWorld;

BEGIN

WRITELN('Hello World');

END.

PASCAL

print "Hello World"

PRINT “Hello World”

Basic, Python, Ruby, Perl

SELECT 'Hello World'

SQL

BEGIN

DBMS_OUTPUT.put_line('Hello World');

END;

PL/SQL

Report Hello_World.

Write: "Hello World".

ABAP

io:fwrite("Hello World~n").

Erlang

IDENTIFICATION DIVISION.

PROGRAM-ID. HelloWorld.

AUTHOR. Fabritius.

ENVIRONMENT DIVISION.

CONFIGURATION SECTION.

INPUT-OUTPUT SECTION.

DATA DIVISION.

FILE SECTION.

WORKING-STORAGE SECTION.

LINKAGE SECTION.

PROCEDURE DIVISION. DISPLAY "Hello World". STOP RUN.

COBOL

% Hello World

/Courier findfont

28 scalefont

setfont

0 0 moveto

(Hello World) show

showpage

Postscript

/(?ms)"((?>[^\"]+)?(?>\.[^\"]*)*)/

Regex – Regular Expression

describe ArticlesController, " GET index" do

it "should be successful" do

get "index"

response.should be_success

end

if "should set @articles" do

Article.should_receive(:find).and_return(mock('articles'))

get "index"

assigns[:articles].should_not be_nil

end

RSpec on Ruby - Language of testing from TDD to BDD

>gi|2501594|sp|Q57997|Y577_METJA PROTEIN MJ0577MSVMYKKILYPTDFSETAEIALKHVKAFKTLKAEEVILLHVIDEREIKKRDIFSLLLGVAGLNKSVEEFENELKNKLTEEAKNKMENIKKELEDVGFKVKDIIVVGIPHEEIVKIAEDEGVDIIIMGSHGKTNLKEILLGSVTENVIKKSNKPVLVVKRKNS

BLAST query

aspect VisitAspect {

void Point.acceptVisitor(Visitor v) {

v.visit(this);

}

}

AspectJ

<bean id=" theCuckoosEggAdvisor " class="org.springframework.aop.support.RegexpMethodPointcutAdvisor">

<property name="advice">

<ref local=" theReplacementFeaturePart1Advice "/> </property>

<property name="pattern"> <value> IBusinessLogic.* </value>

</property>

</bean>

<bean id=" theReplacementFeaturePart1Advice " class=" CuckoosEgg "/>

SpringAOP

<html>

<head>

<title>Hello World</title>

</head>

<body>

Hello World

</body>

</html>

Of course – HTML!

What is DSL?

No standard definition

Specific vs General depends on point of view

VB vs VBA

It helps revealing intentions

Language that domain experts understand

It becomes more and more popular because of tooling support

You can apply DSLs to solve your problems

You can even create your own DSL!

DSL Examples Telecom Adhersion Business Natural Language BNL Pattern Matching Regex Object Relational Mapping Hibernate Publishing Postscript Database Manipulation SQL Domain DSL

DSL – Telecom App Framework Adhearsion (open source telecom application framework) + Asterisk (open source telephony platform)

LEL – Layout Expression Language

layout = " [ label_1 | label3 ]

[ (300,300)*text1 | (150)people ]

[ <label2 | _ ]

[ message | buttons ] "

Source: http://pphetra.blogspot.com/2007/07/lel.html

When to justify DSL

Repeated need of solutions to particular problems

You have a good understanding of problem domain

There is a ready-to-use DSL in that domain

Or if you have to invent one…

What should it look like?

Example - Coffee Order DSL

Starbucks Coffee Order (*)

“ Venti half-caf, non-fat, no foam, no whip latte”

Traditional Implementation

(*) Agile DSL Development in Ruby – Obie Fernandez (http://obiefernandez.com)

Problems with the example

Depends on APIs

Code does not match the way the domain is described

Still difficult to read and verify

DSL style

Reveal intention better

Take advantage of Ruby features

Untyped declaration

No parenthesis parameter

Metaprogramming support i.e. create class methods on the fly etc.

Coffee Order DSL in Java

API approach

CoffeeOrder order = new Latte(VENTI, HALF_CAF, NONFAT_MILK);

CoffeeOrder coffee = order.prepare(false);

DSL approach

CoffeeOrder order = new Latte().size(VENTI).caffeine(HALF).milk(NONFAT).foam(FALSE);

CoffeeOrder coffee = order.prepare();

How about other representations?

XML

<Order type=“Latte”>

<caffeine>half</caffeine>

<milk>nonfat</milk>

<foam>false</form>

<whip>false</whip>

</Order>

English

“ Venti half-caf, non-fat, no foam, no whip latte”

“ Venti latte with no whip cream, no foam, non-fat milk, half-caffeine”

Types of DSL

Internal DSL

Use an existing “host” programming language to describe DSL

Leverage host compiler/interpreter

Some programming languages are better for describing DSL e.g. dynamic languages; some use metaprogramming / annotations

External DSL

Define your own format of the language

Use XML along with XSD or DTD

Must create your own parser/interpreter

Or use DSL tools

External DSL

Business Natural Language (BNL)

“ exclude offer 30 percent cli if d score is less than or equal to 2”

Custom DSL

show us-state field when country select box is "United States"

show province field when country select box is "Canada"

show brutus when us-state select box is "Ohio" or "Michigan"

DSL Design

DSL is not just API

show us-state field when country select box is "United States"

show province field when country select box is "Canada"

show brutus when us-state select box is "Ohio" or "Michigan"

JavaScript Solution #1

create_dynamic_field("show", "us-state-field", "country", "United States");

create_dynamic_field("show", "province-field", "country", "Canada");

create_dynamic_field("show", "brutus", "state", ["Ohio", "Michigan"]);

JavaScript Solution #2

show("us-state-field").when("country").is("United States");

show("province-field").when("country").is("Canada");

show("brutus").when("us-state").is("Ohio, Michigan");

DSL Tools

Martin Fowler coined the term “Language Workbench”

Provide GUI frontend, metamodeling and/or code generation to define and use DSL

Microsoft DSL tool for Visual Studio

Intentional Software

Eclipse EMF

JetBrains Meta Programing System

MS DSL Tool for VS Studio Tutorial: Applying Domain-Specific Modeling to Game Development with the Microsoft DSL Tools. André W. B. Furtado, André L. de M. Santos

Metacase’s MetaEdit+ http://www.metacase.com/fs.asp?vasen=vasen.html&paa=cases/dsm_examples.html

Jetbrains Meta Programming System (MPS)

Summary

DSL is one way to increase a level of abstraction

DSL developers define syntax and semantics to express solutions closer to the domain problem

Using DSL tools

Creating parser/interpreter

Embedding to host languages

DSL users can be either programmers or domain experts

Summary

Types of DSL

Internal DSL

People start to use dynamic languages to create DSL

Ruby on Rails/Grails, Rake (Make on Ruby)

External DSL

Design is important

Consult with domain experts

Further Information

Wikipedia’s DSL http://en.wikipedia.org/wiki/Domain-specific_programming_language

Martin Fowler’s Bliki on DSL http://martinfowler.com/bliki/dsl.html

Language Workbenches: The Killer-App for Domain Specific Languages? http://martinfowler.com/articles/languageWorkbench.html

Obie Fernandez’s Agile DSL Development in Ruby (http://obiefernandez.com/presentations/obie_fernandez-agile_dsl_development_in_ruby.pdf)

Sergey Dmitriev’s Language Oriented Programming: The Next Programming Paradigm (www.onboard.jetbrains.com/is1/articles/04/10/lop/mps.pdf)

Q&A Thai’s resources Narisa.com’s Design & Analysis forum ThaiDev.org

Backup slides

LEL Sample – JRuby

require 'profligacy/swing‘

require 'profligacy/lel‘

module Test

include_package 'javax.swing'

include Profligacy

layout = " [ label_1 | label3 ]

[ (300,300)*text1 | (150)people ]

[ <label2 | _ ]

[ message | buttons ] "

ui = Swing::LEL.new(JFrame,layout) do |c,i|

c.label_1 = JLabel.new "The chat:"

c.label2 = JLabel.new "What you're saying:"

c.label3 = JLabel.new "The people:"

c.text1 = JTextArea.new

c.people = JComboBox.new

c.message = JTextArea.new

c.buttons = Swing::LEL.new(JPanel, "[send|hate|quit]") do |c,i|

c.send = JButton.new "Send"

c.hate = JButton.new "Hate"

c.quit = JButton.new "Quit"

end.build :auto_create_container_gaps => false

end

ui.build(:args => "Simple LEL Example“)

end

view layout [

title “Sample GUI”

a: area

b: button “Fetch URL”

[ r: read http://www.bofh.org.uk

a/text: r

show a

]

button “Close” [unview]

]

Rebol

DDJ Article on Rebol - http://www.ddj.com/184404172

indexing

title: "Hello World";

author: "Michael Neumann";

class MAIN creation

make

feature

make is

do

io.put_string("Hello World");

io.new_line

end -- make

end -- class MAIN

Eiffel

module HelloWorld (main) where

main = putStr "Hello World "

Haskell

'Hello World' out.

Smalltalk

(print "Hello World")

LISP

?- write('Hello World'), nl.

Prolog

<%@ language="javascript" %>

<html><body>

<%

Response.Write('Hello World!');

%>

</body></html>

JavaScript

using System;

class HelloWorld {

static void Main() {

Console.WriteLine("Hello World");

}

}

C#

puts "Hello World"

Tcl, Ruby

documentclass[a4paper]{report}

itle{Hello World}

egin{document}

Hello World

end{document}

LaTeX

Domain Specific Languages

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