Composing Domain-Specific Languages

Composing Domain-Speciﬁc Languages Eelco Visser Delft University of Technology http://eelcovisser.org 12/11/2009 Technical University Eindhoven

Software Engineering implement Problem Solution Domain Domain validate

Programming Languages

Abstraction Scala Programming Languages machine

Abstraction Scala garbage collection objects Programming Languages expressions structured control-ﬂow procedures machine

Problem GPL Machine Domain

The Next Level of Abstraction? Formal Methods

Spec Problem GPL Machine Domain

The Next Level of Abstraction? Domain-Speciﬁc Languages

The Next Level of Abstraction? SQL Domain-Speciﬁc Languages CFG (BNF) RegExp

Problem DSL GPL Machine Domain Domain-Speciﬁc Languages: Specialization

Software System Composition of Specialized Sub-domains

Software System Separation of Concerns Composition of Specialized Sub-domains

Loose Coupling Lack of consistency checks

Thesis Separation of Concerns requires Linguistic Integration

Case Study World Wide Web

where does that link point? is that URL unique? who may edit this entry? where is data stored?

request Client Server response Architecture

quest Convert Request Access Control Validate Forms Parameters Render Page Or Handle Actions Redirect ponse Update Database

Access Data Navigation quest Convert Request Control Validation Access Control Validate Forms Parameters Forms Data Model Actions Render Page Or Handle Actions Redirect ponse Object Page Data Binding Relational Templates Mapping Update Database

Access Data Navigation Control Validation Forms Data Model Actions Object Page Data Binding Relational Templates Mapping (Some) Concerns in Web Applications

Access Data Navigation Control Validation Data Forms Actions Model Object Page Data Relational Templates Binding Mapping data model entity class classes orm JPA active record actions Java/Seam Ruby data validation navigation servlets controllers page templates JavaServer Faces forms JSF tags embedded html data binding JSF + Seam access control Acegi

Access Data Navigation Control Validation Data Forms Actions Model Object Page Data Relational Templates Binding Mapping <s:link view="/entry.xhtml" value="#{entry.title}" propagation="none"> <f:param name="entry" value="#{entry.id}"/> </s:link> @Name("entry") public class EntryBean implements EntryBeanInterface { @RequestParameter("entry") private Long entryId; }

Access Data Navigation Control Validation Data Forms Actions Model Object Page Data Relational Templates Binding Mapping map.root :controller => "homme" # should be "home" http://zef.me/2308/when-rails-fails

Access Data Navigation Control Validation Data Forms Actions Model Object Page Data Relational Templates Binding Mapping data model entity class classes orm JPA active record actions Java/Seam boilerplate code Ruby data validation navigation loose coupling servlets controllers page templates JavaServer Faces forms no/little consistency checking JSF tags embedded html data binding JSF + Seam access control Acegi

Access Data Navigation Control Validation Data Forms Actions Model Object Page Data Relational Templates Binding Mapping - separate languages for separate concerns - linguistically integrated - compile-time consistency checking - 100% code generation (no scaffolding)

Access Data Navigation Control Validation Forms Data Model Actions entity Blog { name :: String (id) Object Page Templates Data Binding Relational entries -> Set<Entry> Mapping authors -> Set<User> } entity Entry { url :: String (id) title :: String (name) text :: WikiText blog -> Blog (inverse=Blog.entries) author -> User (inverse=User.entries) created :: DateTime } entity User { username :: String password :: Secret blogs -> Set<Blog> (inverse=Blog.authors) entries -> Set<Entry> (inverse=Entry.author) }

Access Data Navigation Control Validation Data Forms Actions Model Object Page Data Relational Templates Binding Mapping deﬁne page entry(e : Entry) { header{output(e.title)} output(e.text) “Posted by “ output(e.author) “ on “ output(e.created) navigate(editentry(e)){“Edit”} }

Access Data Navigation Control Validation Data Forms Actions Model deﬁne page editentry(e : Entry) { Object Page Data Relational Templates Binding Mapping form{ input(e.url) input(e.title) input(e.text) input(e.author) input(e.created) action(“Save”, action{ return entry(e); }) } }

Access Data Navigation Control Validation Data Forms Actions Model Object Page Data Relational Templates Binding Mapping entity Entry { url validate(isUniqueEntry(this), “Entry with that URL already exists”) }

Access Data Navigation Control Validation Forms Data Actions access control rules Model Page Data Object Relational principal is User Templates Binding Mapping with credentials username, password rule page entry(e : Entry) { !e.private || principal in e.blog.authors } rule page newentry(b : Blog) { principal in e.blog.authors } rule page editentry(e : Entry) { e.author == principal }

Access Data Navigation Control Validation Data Forms Actions Model Object Page Data Relational Templates Binding Mapping - separate languages for separate concerns - linguistically integrated - compile-time consistency checking - 100% code generation (no scaffolding) - order of magnitude decrease in code size

http://researchr.org

Access Data Navigation Control Validation Data Forms Actions Model Object Stratego/XT Page Data Relational Templates Binding Mapping Domain-Speciﬁc Language Engineering

Access Data Navigation Control Validation Data Forms Actions Model Object Stratego/XT Page Data Relational Templates Binding Mapping WebDSL Java

Access Data Navigation Control Validation Data Forms Actions Model Object Stratego/XT Page Data Relational Templates Binding Mapping Core WebDSL Java WebDSL

Access Data Navigation Control Validation Data Forms Actions Model Object Stratego/XT Page Data Relational Templates Binding Mapping Python Core WebDSL Java WebDSL C#

Access Data Navigation Control Validation Data Forms Actions Model Object Stratego/XT Page Data Relational Templates Binding Mapping Python Core WebDSL PIL Java WebDSL C#

Access Data Navigation Control Validation Data Forms Actions Model Object Stratego/XT Page Data Relational Templates Binding Mapping Component-Based Language Engineering DM PIL Python UI PIL AC PIL + WebDSL Core WebDSL PIL Java C# DV PIL

Access Data Navigation Control Validation Data Forms Actions Model Page Data Object Relational - separate languages for separate concerns Templates Binding Mapping - linguistically integrated - compile-time consistency checking - 100% code generation (no scaffolding) - order of magnitude decrease in code size http://webdsl.org http://strategoxt.org http://researchr.org

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Composing Domain-Specific Languages

by Eelco Visser on Nov 12, 2009

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