A Model-Driven Approach to Generate External DSLs from Object-Oriented APIs

Valerio CosentinoMassimo Tisi

Javier Luis Canovas Izquierdo

SOFSEM, 2015, Pec pod Sněžkou, Czech Republic

A Model-Driven Approach to Generate External DSLs from Object-Oriented

APIs

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Outline

Introduction

Model Driven Engineering

From API to DSL

Conclusion and Future work

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Introduction

Code abstraction and reuse allow the use of existing software knowledge (i.e., code libraries) to build new software by reducing:– Time– Resources– Redundancy

Code libraries can be accessed via:– APIs using mechanisms (function call, class

inheritance, etc.) provided by the General-purpose Programming Language (GPL)

– DSLs (Domain Specific Languages)

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Introduction

API vs DSL:

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Introduction

Are DSLs better than APIs?[1]– Pros:

DSLs can be more expressive, maintainable, concise and readable

Static validation, syntax highlighting, etc. Interpretation/compilation optimized for the DSL code execution

– Cons: DSLs requires a higher development cost

[1] Kelly, S., Tolvanen, J.P.: Domain-Specific Modeling: Enabling Full Code Generation. Wiley IEEE Computer (2008)

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Introduction

How to reduce the development cost when building a DSL?–Model Driven Engineering (MDE)

Automatic generation of DSL components:– compiler, validator, development environment

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Model Driven Engineering

What is MDE?– Models: first class entities in MDE (abstract

representation of the knowledge for a given domain)– Model transformations: operaration for model handling

Injectors/extractors to move between technical spaces [2]

[2] Kurtev, I., Bezivin, J., Aksit, M.: Technological Spaces : an Initial Appraisal. In: DOA. (2002) 1–6

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From API to DSL

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From API to DSL

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From API to DSL

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API classes to API metamodel

Mapping[3]– API class definitions metamodel elements– Java classes metaclasses

Attributes metaclass attributes Methods operations

Customization:– Some APIs can generate very large

metamodels Selection of a subset of API elements

– Tunable API metamodel Manual modifications

[3] Canovas Izquierdo, J.L., Jouault, F., Cabot, J., Garcıa Molina, J.: API2MoL: Automating the building of bridges between APIs and Model-Driven Engineering. Inform. Software Tech. 54(0) (2012) 257–273

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From API to DSL

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API metamodel to DSL metamodel

Domain-specific concepts extracted from the API metamodel

Domain-independent API structure– Templates

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Templates

Plain Old Data (POD)– For simple APIs to create and maintain a

data structure– API classes composed by getters, setters

and constructors

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Templates

Fluent– For APIs that rely on chaining method calls– The return values of the method calls

(keywords) are used to structure the DSL

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Templates

SimpleJava– For APIs that do not fit in the previous

categories– Java sub-set(statements, declarations, etc.)

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From API to DSL

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DSL metamodel to DSL tooling

Bridge between the Model TS and the Grammar TS– Mapping of metamodel elements into the grammar

rules– Development environment

The generation process is parameterized by:– The DSL metamodel (concepts, attributes,

references, cardinalities, etc.)– The template chosen (the grammar structure, the

development environment and compiler)– Particularized for Xtext[4]

[4] Eysholdt, M., Behrens, H.: Xtext: implement your language faster than the quick and dirty way. In: SPLASH. (2010) 307–309

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From API to DSL

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Compiler generation

Since the semantics of the DSL template is known, a DSL instance can be transformed into its equivalent in Java– SimpleJava

DSL concepts have a one-to-one correspondence with Java constructs

DSL model to Java model (MoDisco[5]) Java model to Java readable file (Acceleo[6])

[5] http://www.eclipse.org/gmt/modisco/technologies/J2SE5/|6] http://www.eclipse.org/acceleo

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Conclusion and Future work

MDE approach to connect API, Model and Grammar technical spaces

Template mechanism to generate the resulting DSL Proof of concept

Future work:– Identify more templates to cover other types of

DSLs (API characterization)– Study how our method could cope with more

complex APIs (event-driven, concurrent, etc.)– Explore how distinct APIs used in the same GPL can

be combined at DSL-level (interleaving DSLs)

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