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MontiCore - Language Workbench And Development Tool Framework

MontiCore is a language workbench for an efficient development of domain-specific languages (DSLs). It processes an extended grammar format which defines the DSL and generates Java components for processing the DSL documents. Examples for these components are parser, AST classes, symboltables or pretty printers. This enables a user to rapidly define a language and use it together with the MontiCore-framework to build domain specific tools.

Some MontiCore advantages are the reusability of predefined language components, conservative extension and composition mechanisms and an optimal integration of hand-written code into the generated tools. Its grammar languages are rather comfortable.

A Teaser for MontiCore

To show a little of MontiCore's capabilities, the following (incomplete) grammar might help:

grammar MyStatemachine extends Automata,                  // MontiCore grammar 
                               MCBasicTypes, SetExpressions, MCCommonLiterals {     
  start Automaton;

  // overriding a nonterminal (to add optional conditions):
  Transition = from:Name@State ":" Expression? "->" to:Name@State;

  // add new variants of expressions
  LogicalNotExpr implements Expression = "!" Expression;

  XorExpr        implements Expression =
        left:Expression "xor" right:Expression;

  scope LetExpr  implements Expression =
        "let" (VarDeclaration || ",")+ "in" Expression;

  symbol VarDeclaration = MCType? Name "=" Expression ;
}

The grammar language has a variety of mechanisms to define new nonterminals using constants "!", brackets (..), optionals ?, lists *, repetitions (..||..)+, etc. The grammar builds an extended version of Statemachines reusing existing grammar components, here Automata, MCBasicTypes, SetExpressions and MCCommonLiterals. The grammar has 5 productions introducing 4 new nonterminals and overrides Transition, which is inherited from Automata. Transition additionally has an optional Expression? as firing condition. LogicalNotExpr, XorExpr, and LetExpr extend the already existing Expression nonterminal and add new forms of expressions.

LetExpr introduces a new local variable, which is visible only in that scope (indicated by keyword). VarDeclaration defines the new place to define symbols (that have a Name). There is an extensive infrastructure to manage the definition of names, visibility, etc.

MontiCore compiles the above grammar into 78 classes with in total 18629 lines of code that define the complete frontend and a larger part of the backend of a statemachine processor. We now can write statemachines like:

statemachine PingPong {                                         // MyStatemachine
  state Ping, Pong;
  Ping : (speed > 14km/h && !missedBall) -> Pong
}

MontiCore provides versions of expressions that use SI Units like 240km/h or 14.2 m/s^2, but also Java expressions like 2_000_000 and other variants including appropriate type checks. We include these forms of expressions by importing their grammars.

Please note that in both cases (extension and overwriting existing nonterminals), we do not touch nor copy/paste the predefined grammars, but achieve an out-of-the-box reuse. Out-of-the-box reuse also includes reuse of predefined typechecks, code generation, etc. They only need to be extended to the added variants. Please also note that PlusExpr is mutually left-recursive. -- Yes, that works in MontiCore 6.

More Information about MontiCore

  • MontiCore Online Demonstrator. (TODO: needs to be released)

  • MontiCore Reference Manual. The reference Manual describes how to use MontiCore as a out-of-the-box language workbench), but also as grey box tooling framework. It thus also gives an overview over a number of core mechanisms of MontiCore.

  • List of core grammars. MontiCore concentrates on reuse. It therefore offers a set of predefined language components, usually identified through an appropriate component grammar allowing to define your own language as a composition of reusable assets efficiently. reusable assets are among others: several sets of literals, expressions, types, and statements, which are freely composable.

  • List of languages. This is a list of languages that can be used out of the box. Some of them are in development, others rather stable. Several of these languages are inspired by the UML/P (see [Rum16,Rum17]. These complete languages are usually composed of a number of language components.

MontiCore 3-Level License on files (informal description)

Summary: This project is freely available software; you can redistribute the MontiCore language workbench according to the following rules.

Details: The MontiCore Languag Workbench deals with three levels of code (MontiCore, tool derivates, product code). Each with different licenses:

  • Product code: when you use a MontiCore tool derivate to generate code, the generated code is absolutely free for each form of use including commercial use without any license.

  • Tool derivate: when you derive a tool using the MontiCore language workbench, then you mention that it is a MontiCore derivate. There is no other restriction. (BSD 3 Clause license)

  • MontiCore adaptations: you may also freely adapt MontiCore itself, but then you have to mention MontiCore AND the resulting code is to be pushed back into this LPGL repository (LGPL license).

As a consequence using MontiCore during development is rather flexible and the final products do not have any restriction.

If questions appear e.g. on building an interpreter, please contact monticore@se-rwth.de.

General disclaimer

(Repeated from the the BSD 3 Clause license):

This software is provided by the copyright holders and contributors "as is" and any expressed or implied warranties, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose are disclaimed. In no event shall the copyright holder or contributors be liable for any direct, indirect, incidental, special, exemplary, or consequential damages (including, but not limited to, procurement of substitute goods or services; loss of use, data, or profits; or business interruption) however caused and on any theory of liability, whether in contract, strict liability, or tort (including negligence or otherwise) arising in any way out of the use of this software, even if advised of the possibility of such damage.

Included Software

This product includes the following software: * AntLR * FreeMarker

Contribution

When you want to contribute: Please make sure that your complete workspace only uses UNIX line endings (LF) and all files are UTF-8 without BOM. On Windows you should configure git to not automatically replace LF with CRLF during checkout by executing the following configuration:

git config --global core.autocrlf input

Further Information