object constraint language in together dan massey y&l consulting
TRANSCRIPT
Object Constraint Language
in Together
Dan Massey
Y&L Consulting
Picking up From Logicians
Follows 3242 presentation to go in depth on OCL and using OCL in tools
The preconference tutorial used the slides from session 3242 as the first third of the presentation.
OCL Topics
OCL Basics
The LiquidLemons Example
OCL in Together
Team Modeling Exercise
OCL Topics
OCL Basics
The LiquidLemons Example
OCL in Together
Team Modeling Exercise
OCL is
Strongly typed declarative language
Small set of built-in types, including collections
User-defined types and operators
OCL Basic Types
Boolean true or false
Integer theoretically unlimited natural numbers, subtype of Real
Real mathematical Real, no specific
implementation implied
String ‘sequence of characters’
Boolean Operations
a : Boolean b : Boolean
a and b a or b a xor b
not a a = b a <> b
a implies b
implies constraint:
if a is true then b must be true
Numeric Operators
Comparison
= equals <> not equals
< less > more
<= less or equal >= more or equal
Math
+ addition - subtraction
* multiplication / division
Every Type in OCL is an Object
a : Integer b:Integer
a.mod(b) a.div(b)
a.abs() a.max(b)
a.min(b) a.round()
a.floor()
Operators are just infix notation operations.
String Operations
a : String b : String
a = b a <> b
a.concat(b) a.size()
a.toLower() a.toUpper()
a.subString(1, 3)
Operations return new Strings.
OCL Conditional
OCL provides one conditional construct:
if <Boolean expression>
then <expression>
else <expression>
endif
No “elseif” or “switch”/“case”
OCL Operation Precedence
Grouping ()Path resolution ::Message notation . -> also ^ ^^Unary - notMultiplication/Division * /Addition/Subtraction + -Comparison < > <= >= <> =Logical and or xorLogical implication implies
User-Defined Types
Classes, Interfaces, etc. defined in the model
Users may overload infix and unary operators:
Multiply Money by a Real
Add two Distance values
OCL Collections
Refreshing our memories, we have:
Collection
Bag Sequence
Set OrderedSet
OCL allows you to treat any instance like a collection. You can ask if a single attribute is empty.
Collections must by Typed
Set(Bid)
Bag(String)
Like generics in Java or templates in C++.
Collections Literals
Use curly brackets around comma lists to specify Collection literals.
Bag {‘sock’, ‘sock’, ‘shirt’, ‘sweater’, ‘sock’}
Sequence {‘abe’, ‘bob’, ‘bob’, ‘tim’, ‘zak’}
Set {16.0, 2.0, 64.0, 8.0, 128.0, 3.5}
OrderedSet {1, 2, 4, 8, 16, 32, 64, 128}
You can also specify Collections of Collections.
Basic Collections Operations
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 +
More Collections Operations
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
Flatten
Recursively adds the members of nested collections to a single collection.
context MyTypedef: a : Set(Set(Integer)) =
Set {Set{1, 2, 3}, Set{3, 4, 5}, Set{4, 5, 6}}
a->flatten() = Set{2, 3, 1, 5, 4, 6} -- no order
Collection Loops
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)
Other OCL Types
OclAny the root Type
OclVoidthe “null” Type “undefined”
OclType a type, like “Class” in Java
OCL provides operations for type identification.
Tuple group of named values
Tuple {name : String = ‘Dan’, role : Role = Role::Speaker}
OCL Topics
OCL Basics
The LiquidLemons Example
OCL in Together
Team Modeling Exercise
Liquid Lemons Domain
LL Invariantscontext Sale-- a Sale has one or more itemsinv numberOfSaleItems : items->size() > 1
-- a Sale's subtotal may not be less than zeroinv subtotalGreaterThanZero : subtotal().amount >
0.0 and subtotal().currency = Currency::USDollars
LL Pre and Postcontext LiquidLemons::addLemonade(flavor :
Flavor, size : DrinkSize)pre activeSale : currentSale->size() = 1pre mustHaveFlavor : not flavor.oclIsUndefined()pre mustSpecifySize : not size.oclIsUndefined()post newLemonade :
currentLemonade->size() = 1
LL Query
Collections Queries
context ItemAnalyzer::averagePrice() : Moneybody: items.basePrice()->sum() /
items.basePrice()->size()
context ItemAnalyzer::uniqueModDescriptions() : Set(String)
body: items.modDescriptions() ->flatten()->asSet()
Composite QueriesUse small methods with single responsibilities to build up
larger functions.
-- the total we want is subtotal plus taxcontext Sale::total() : Moneybody: subtotal() + tax()
-- tax is the subtotal times the local tax ratecontext Sale::tax() : Moneybody: subtotal() * Tax::localRate
Composite Queries Cont.context Sale::subtotal() : Moneybody: items.price()->sum()
context LineItem::price() : Moneybody: basePrice() + modsPrice()
context LineItem::modsPrice() : Moneybody: modifiers.price()->sum()
Don’t Do Thiscontext LineItem::basePrice() : Moneybody: if size = DrinkSize::Small then if flavor = Flavor::Regular then Money::newInstance(1.23, Currency::USDollars) else Money::newInstance(1.73, Currency::USDollars) endif else if flavor = Flavor::Regular then Money::newInstance(2.43, Currency::USDollars) else Money::newInstance(3.13, Currency::USDollars) endif endif
Use Polymorphism
Little policy classes are an extension of the little operations idea. Smaller rules are easier to read.
context LargeRegularLemonade::basePrice() : Moneybody: Money::newInstance(2.43, Currency::USDollars)
context SmallFlavoredLemonade::basePrice() : Moneybody: Money::newInstance(1.72, Currency::USDollars)
OCL Topics
OCL Basics
The LiquidLemons Example
OCL in Together
Team Modeling Exercise
Where Does the OCL Go?
Use the named property fields and boxes.
Shows up in generated docs and XMI export.
Not visible in diagrams.
OCL Notes
Attach notes containing OCL to correct contexts.
OCL is visible in the diagrams.
Potential to clutter the model.
Together Designer
Syntax checked OCL in “Constraint Notes” that establish context.
Now in field test.
OCL Topics
OCL Basics
The LiquidLemons Example
OCL in Together
Team Modeling Exercise
Domain Options
Tic-Tac-Toe
Ants
Electronic Voting
Poem
Golf
Turtle Logo
Dog Kennel