TMF Xtext – Textual Modeling Framework. ▫ Provides a DSL, runtime and tools
for building textual editors. ▫ EMF is used as the underlying target language.
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
TMF Xtext – Textual Modeling Framework
Provides a DSL, runtime and tools for building textual editors
EMF is used as the underlying target language
Ecore model is implicitly defined by the grammar or existing EMF models may be used
Grammar covers:
lexical syntax (terminals)
rules for syntactic structures
relation between syntax and Ecore classes
1
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Xtext – grammar file
Define the grammar name and specify existing grammar to inherit from
Either generate or import Ecore model
generate
import as
Define terminal
grammar with
terminal ‘:’ ‘;’
Define syntax rule
‘:’ ‘;’
2
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Xtext – syntax rules
Each rule implicitly defines an Eclass
‘:’ ‘;’ defines an EClass named
Elements in the syntax defintion define EAttributes and EReferences for the rule’s Eclass
= defines an EAttribute
= defines a containment EReference
=‘[‘’]’ defines an EReference
+= is used instead of = to indicate multiple values
?= indicates a boolean EAttribute
Syntax is based on BNF
literal keywords
grouping with ()
optionality with ? and multiplicity with * and +
alternatives with | 3
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Xtext – building an EMF-based parse tree
Parsing process
the parsing process relates the input to the grammar rules
when the input matches a rule, actions that build an abstract syntax tree are performed
Xtext’s AST is a tree of instances of the Ecore model
Editing and parsing
during editing, the input is continuously (re)parsed
parse errors are (silently) indicated by error markers
valid input results in a complete tree of Ecore objects
4
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Language concepts
State
name
sub-states
transitions
variables
definitions for script-based events, conditions and actions
Transition
external, between states
internal, used to trigger actions within a state
event, condition, action
event, condition
initial, default transition when entering parent state
condition, action 5
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Language syntax
State
either just a name or content within braces { }
Transition
internal, actions triggered by transitions or states
initial, default transition when entering parent state
name!, event script reference, source -> target, source-> or target target when event [ condition ] / action
Event
-> target when [ condition ] / action
external, between states
action when event [ condition ]
name! or action script reference
Condition
condition script reference 6
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Create an Xtext project
7
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
The xtext grammar
Generated projects and files
grammar is initialised to an example grammar
grammar project
grammar compiler
grammar
generator project
The grammar project
defines a grammar
contains files generated from the grammar
The generator project
used for impl. transformations on instance files (more later) 8
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
First tentative grammar
grammar statement
the grammar name
inherit from existing grammar, here the default lexical syntax
generate statement
the name and URI of the generated Ecore model
StateMachine
a sequence of States
contained in an Ereference named states
State
an identifier followed by a semicolon
set as the value of an EAttribute name name
9
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Run the MWE workflow
10
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Examine generated Ecore model
An Ecore model is generated (and lots of code)
For each grammar element there is a corresponding Ecore model element
rule corresponds to EClass
rule reference corresponds to EReference
terminal rule reference corresponds to EAttribute
11
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Try the grammar...
Start new Eclipse
Create text file and open with generated editor
12
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TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Try the grammar...
Enter example text
Open as Ecore data
13
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Examine text’s correspondance with Ecore data
The text file as a whole corresponds to the root class, here StateMachine
Each ID ‘;’ matches the State rule and results in a State instance
The states’s name is set to the ID terminal
14
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Development instance of Eclipse
The big picture
Xtext grammar / model
Generated Ecore model
Xtext instance
Ecore instance
Test instance of Eclipse
15
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Extend to grammar
Transitions
from a source state to a target state
uses the [State] notation to refer to states by name (ID)
A StateMachine can contain
one or more states
zero or more transitions
16
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Try the grammar once more
Generate (and examine) the Ecore model
Run the Eclipse instance and edit the example text
17
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Extend to grammar once more
Allow alternating states and transitions
instead a sequence of states followed by transitions, we now allow a sequence of a state or a transition
Support hierarchical states
the same content as a StateMachine within braces { } 18
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Try the grammar once more
Generate (and examine) the Ecore model
Run the Eclipse instance and edit the example text
19
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Extend to grammar once more
Support another kind of transition: initial transition
I.e. a Transition is an ExternalTransition or an InitialTransition
Interpreted as (disjoint) specialisation, i.e. inheritance from a base class
Common EAttributes and EReferences are pushed up into the base class 20
Q
TDT4250 - Model-driven Development of Information Systems, Autumn 2009
Try the grammar once more
Generate (and examine) the Ecore model
Run the Eclipse instance and edit the example text
21
Q
