m2t with xpand and xtend - · pdf filem2t with xpand and xtend . 2 ... example: xtext-based...

Meta.ppt 1

TDT4250 - Model-driven Development of Information Systems, Autumn 2009

M2T with Xpand and Xtend

2


Q

M2T - model-to-text transformations

Why so common?

text is a ubiquitous format

many tools uses text as source, intermediary and target format

although text languages are formal, there may not be an

explicit meta-model available

Problems

confusing to mix source and target languages,

i.e. text as output and text as code

encoding issues

less control of the transformation process, e.g. back-patching,

post-processing, transformation chaining, etc.

3


Q

Example: Xtext-based state lang. to SCXML

Source language

defined using Ecore

concrete syntax defined with Xtext grammar

Target language

SCXML, an XML-based language defined by W3C:

http://www.w3.org/TR/2009/WD-scxml-20091029/

text-based, but has an XML Schema, so we can effectively

derive an Ecore model

Two possibilities

transform directly to text

transform til Ecore model and serialize

4


Q

Example: Xtext-based state lang. to SCXML

Transformation

source and target models have similar concepts

states, transitions, events, conditions, actions

some differences

internal transitions correspond to transitions without a target

enter and exit actions are modeled as internal transitions

what about and-decomposition?

implicit in the source language

explicit in SCXML: <parallel> ... </parallel>

scripting

scripts occur in events, conditions and actions

mostly support in SCXML (extension)

5


Q

Main elements of Xpand/Xtend transformation

Import of model

So-called

extension functions

written using the Xtend sub-language

side-effect-free helper methods that are used by the template

Template methods

text fragments that are copied to the output

everything that are not enclosed in french quotes << >>

expressions that are evaluated and written to output

control structures

6


Q

Extension functions

Highly inspired by OCL

based on expressions, not imperative code

side-effect-free, but can can change collection values

Matches methods based on types

7


Q

Xpand control structures

if else endif

conditional execution

let as

bind local variables

foreach

part of call to template method, for iterating over collection

expression sequence

the -> operator sequences expressions

allows for more procedural code

8


Q

From scxmlxtext to <scxml>

Import model and

reference Xtend file

Define main entry point

defines the output file

generates the outer <scxml> element

expands the content as a state named “root”

9


Q


A state is tranformed to a <state> element

Expand

all variables

an initial state

allow only 1

all (sub-)states

all transitions

10


Q


The initial transitions is tranformed to an <initial>

element with a inner <transition> element

The transition element may have an action

expand if non-null

11


Q


The <transition> element

targets, events and conditions are string attributes

actions are inner elements

12


Q


The <cs:var> element

apache-specific element, i.e. different namespace

expands init-expression based on expression sub-type

13


Q

Sample output

The <cs:var> element

apache-specific element, i.e. different namespace

expands init-expression based on expression sub-type

14


Q

Sample output

structural view text view

Remove whitespace by inserting – before >>

e.g.

m2t with xpand and xtend - · pdf filem2t with xpand and xtend . 2 ... example: xtext-based...

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