OCL in EMF

OCL in EMF
Ashwani Kr Sharma, SAP Labs India

Agenda
Why OCL ?
What is OCL ?
When OCL ?
OCL in EMF ?

Why OCL ?
There are different categories of jobs,
Each category requires different skills.
Each plumber may have a different
repertoire of skills
Business Rule:
Each Job's assignee's skills include all the Job's category's requirements.
….

UML Solutions
UML 1.x Use your favorite programming language
Ada/C/...
Magically inserted by proprietary code generator
UML 2.x Use a neutral specification language
The Object Constraint Language
State machine guards/actions
Class invariants
Operation bodies, pre/post conditions
Property initial/derived values

Why OCL ?
Business Rule:
Each Job's assignee's skills include all the Job's category's requirements.
OCL-
Job ::assignee.skills-->includes (category.requirements)

Why OCL ?
In object-oriented modeling, a graphical model, like a class model, is not enough for a precise and unambiguous specification
The business rules are not captured.
Natural languages are ambiguous.
Formal languages is are useable to persons with a string mathematical background, but difficult for the average business or system modeler to use

What is OCL ?
Object Constraint Language (OCL), is a formal language to express side effect-free constraints. Users of the Unified Modeling Language and other languages can use OCL to specify constraints and other expressions attached to their models.
OCL is an add-on feature of UML, used to describe constraints, rules, specifications.

What is OCL ?
Natural/Formal Language compromise
natural language error prone
formal language unapproachable to many
Specification (not Programming) Language
declarative, modeling language
side effect free, no model changes, atomic execution
strongly typed, using UML generalization

OCL is typed !
OCL is a typed language, so each OCL expression has a type. In a correct OCL expression all types used must be type conformant

OCL is a pure expression language
OCL expression is guaranteed to be without side effect; it cannot change anything in the model
Whenever an OCL expression is evaluated, it simply delivers a value.

Mathematical operators
Infix: +, -, *, /
and, or, xor, implies =, <>, <, >, <=, >= , =, <>
Prefix: not, -
4.0 * -5
'a' + 'b'
Operators: mod, div, max, min, ...
4.max(5)

OCL Expressions
IfExpressions
if gender = Gender::MALE then 'he' else 'she'endif
Let Expressions
let jack : Person = child('Jack'), jill : Person = child('Jill') in jack <> null and jill <> null

Object Navigation
Properties
self.name or just name(this.getName() or getName())
Operations
self.child('John') or just child('John')(cf. this.child('John') or child('John'))

OCL: So far !
Business rules and requirements can be stated unambiguously
OCL provides a programming-language-neutral way of stating requirements
OCL removes inconsistencies and holes in the less formal requirements documents, forcing important issues to be clarified at an early stage.
OCL is formal language that remains easy to read and write

OCL in EMF
EMF is based on eMOF, a variant of MOF standard from OMG
OCL specification is part of UML specification and is implemented for EMF we well
OCL statements specified as part of EMF Model or invoked directly from programming language e.g. java
Contributed as part of Eclipse MDTOCL
MDTOCL provides support to UML and EMF based models.

Eclipse MDTOCL
Original code contribution by IBM
Java callable API
Parse/evaluate OCL 1.x against Ecore meta-models
Ecore or UML meta-models
Example Interactive Console
For OCL 2.0 as far possible
Towards OCL 2.2
Example Xtext editors (Ecore only)
OMG OCL 1.x
EMFT/OCL 1.0
OMG OCL 2.0
MDT/OCL 1.2
OMG OCL 2.2
MDT/OCL 3.0

Validation History
Use of OCL to define model validation
EMF Validation Framework, Embed OCL in XML CDATA
EMF, OCL EAnnotations
Embed OCL in Eannotation, Genmodel to integrate
Delegates, Embed OCL in EAnnotation
EObject.eInvoke() for dynamic invocation
OCLinEcore editor for semi-validated editing
OMG OCL 1.x
EMFT/OCL 1.0
OMG OCL 2.0
MDT/OCL 1.2
OMG OCL 2.2
MDT/OCL 3.0

OCL IDE: OCLinEcore Editor
Open with -> OCLinEcore
Save As *.ecore
Loses formatting and comments
Save As *.oclinecore
Text file preserves comments
Useful for plain Ecore too:
Printable/reviewable text
Searchable/replaceable text

OCL IDE: OCLinEcore Editor
Maintains EAnnotations automaticallyProvides OCL syntax checkingIn future will provide OCL semantic checking

OCL IDE: Interactive OCL console
Used to run OCL queries and OCL expresssions
Window->Show View->Other... Console.
Console: New: Interactive OCL

OCL Collections
Typed Collections partially reify multiplicities
Collections are different to objects
Navigation from a Collection uses ->
[Navigation from an Object (OclAny) uses .]
Collections have type parameters
Collections have useful operations
Collections have very useful iterations
© SAP 2007 / Page 21

OCL Collections
a : Set(String) b : String c : Set(String)
a = c a <> c
a->size() a->count(b)
a->excludes(b) a->excludesAll(c)
a->includes(b) a->includesAll(c)
a->isEmpty() a->notEmpty()
a->sum() -- contents are of type supporting +

OCL Collections
OCL supports a wide range of Collection operations that vary by Collection type.
first(), last(), at(i : Integer), etc. for {ordered} collections
union(), -, asSet(), including(), symmetricDifference(collection : Collection) are a sample

OCL Collections
OCL supports an iterate() operation for Collections. On top of that idea, OCL provides a set of Collection operations that accept expression.
Examples:
any(expression) exists(expression)
collect(expression) one(expression)
select(expression) reject(expression)

OCL Collections::select
Children
self.children
Sons
self.children->select(gender = Gender::MALE)self.children->select(child | child.gender = Gender::MALE)self.children->select(child : Person | child.gender = Gender::MALE)
select(iterator : type | body)
filters to select elements for which the body is true
reject(iterator : type | body)
filters to reject elements for which the body is true

OCL Collections::iterator
Children
self.children
Grandchildren
self.children->collect(children)self.children->collect(child | child.children)self.children->collect(child : Person | child.children)
collect(iterator : type | body)
creates a new collection comprising all the bodies
any, exists, forAll, isUnique, iterate, one,

More Queries
parents.parents->asSet()->sortedBy(name)
->asSet() converts to Set(Person), removes duplicates
->sortedBy(name) alphabeticizes

Other OCL Capabilities
Other iterators, operations
Tuples
post statement
Association Classes/Qualifiers
@pre values
Messages
States

When OCL ?
None
Very simple modeling
Java augmented modeling
A little
OCL (and Java) augmented modeling
A lot
OCL as a powerful formal specification language
OMG's UML, OCL, QVT, ... specifications
OCL as the foundation of a transformation language
MOFM2T (Acceleo), QVT
OCL as a portable implementation language

OCL Downloads
Install MDT/OCL 3.0.1 Examples and Editors
For links to slides and to zip file comprising, model,edit,editor,diagram projects: use link: http://www.eclipsecon.org/summiteurope2010/sessions/?page=sessions&id=1710
Import ... Existing Projects from Archive
ESEExampleTree/model/People1.ecore
Run nested Eclipse, Import ESEExampleTree
ESEExampleTree/model/default.people_diagram

OCL in EMF

by Ashwani Sharma on May 11, 2011

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OCL in EMF — Presentation Transcript