University of Utah SoC CS 6961 - Lecture 15 1

Inside UML

CS6961 – Lecture 15

Nathan Dykman

University of Utah SoC CS 6961 - Lecture 15 2

Administration

• Grading Started– Please get in HW4, if you haven’t already.

• Okay, topics of discussion coming up:– QA, Testing and Release Engineering

• Metrics

– Reverse Engineering of Complex Systems• Real World Examples

– MDA and SOA – Refactoring– Did I miss anything?

University of Utah SoC CS 6961 - Lecture 15 3

Today’s Lecture

• Today: I’m going to give you a peek behind the UML curtain– Give you an idea of how UML is put together

University of Utah SoC CS 6961 - Lecture 15 4

UML Worries

• The main question people ask after dealing with UML after a while is: “Why it is so complicated?”

• I’m sure you have some of these kinds of questions– Examples?

• This lecture hopes to explain some of the complexity

University of Utah SoC CS 6961 - Lecture 15 5

UML: Incompleteness

• The major part that throws people is that UML allows incomplete models– But, in some cases, complete information

must be provided. (Example?)– Some view this as a major shortcoming

• It is a shortcoming, but not as big as it seems.

– But is incompleteness really bad?• Think about regular code files here.

University of Utah SoC CS 6961 - Lecture 15 6

UML: Incompleteness

• The hard part about UML is that you can’t just save a model in “any old state”– There is work on this, actually.

• But, most tools disallow some kinds of invalid models to be created– But, not all. A model can be semantically

incorrect, but still created in a tool. • Why?

University of Utah SoC CS 6961 - Lecture 15 7

UML: Ambiguity

• One constant annoyance in UML is that if something isn’t there, doesn’t mean it isn’t somewhere.– What’s worse, in some cases, missing

information “assumes” default values, in others, it is merely “unspecified”

• The rule is to assume the least possible– This works in most cases, but not all.

University of Utah SoC CS 6961 - Lecture 15 8

Class Example

Testing

+ anAttribute+ anAttribute : int

+ operation ( )+ operation ( )+ operation ( )

Testing

+ anAttribute+ anAttribute : int

+ operation ( )+ operation ( [in] foo : int )+ operation ( [in] foo : int , [in] bar : string ) : int

Testing

+ anAttribute+ anAttribute : int+ moreAttributes

+ operation ( )+ operation ( [in] foo : int )+ operation ( [in] foo : int , [in] bar : string ) : int

University of Utah SoC CS 6961 - Lecture 15 9

UML: Ambiguity

• This problem comes from a subtle part of UML. Diagrams aren’t models. – A diagram is merely just a view on a model. A

model is complete.– Why is a diagram just a view on a model?

• Programming languages don’t do this, right?

– So, we can view the previous example as three different views on a single class.

• In the model, there is one class

University of Utah SoC CS 6961 - Lecture 15 10

UML: Ambiguity

• The problem is made a more difficult in that there is diagrams are the only UML syntax that tools provide– This made worse by the standard XML format

of UML (XMI)• To my mind: XMI is pretty broken• The latest versions may help address this

– But there are too many versions to deal with in the first place.

University of Utah SoC CS 6961 - Lecture 15 11

Modeling Future

• In the future, it is likely UML and other modeling languages will require better textual formats as well as visual syntax– There is already a standard “human-usable”

format that looks more like code• Sadly, very little support for it.

– Some tools provide a data-grid like editors.– But, we need things like XML, Relational

Schemas, etc.

University of Utah SoC CS 6961 - Lecture 15 12

UML: Complexity

• Another major complaint about UML, is well, there is sure a lot of it– I agree with this. UML could lose some bulk– Main problem is nobody can really agree on

what to cut, and everybody has something they want to add

– UML in the middle of the “second-system” effect

• Hopefully, feature set will shake out with more use

University of Utah SoC CS 6961 - Lecture 15 13

UML: Complexity

• Of course, just because it’s there, doesn’t mean you have to use it– In many cases, a large part of UML is for

specialized audiences• Some talk of making a xUML language for these

advanced bits

– Strive to use the smallest subset that does the job

• But don’t reinvent the wheel either.

University of Utah SoC CS 6961 - Lecture 15 14

UML: Complexity

• As model-driven development moves forward, hopefully the complexity will start to pay off– More complex code generation– Direct model execution or interpretation– Better integration with languages

• For now, certain domains benefit the most– Telecommunications, embedded real-time are

the best examples.

University of Utah SoC CS 6961 - Lecture 15 15

Behind The Curtain

• One common benchmark on computer languages is “can it describe itself”– Some languages make this dead easy

(Scheme)– Others, more complex (Perl Compiler in Perl)– This “benchmark” has major drawbacks

• “Little languages” (Domain specific programming languages) suffer in this area.

University of Utah SoC CS 6961 - Lecture 15 16

The UML Metamodel

• UML is used to describe UML.– Well, in reality, it’s more complex than that– Only a small subset of UML is used currently

• Restricted class diagrams• Object Constraint Language (which has a

metamodel as well)

– Metamodeling still an area of research and development

• My PhD work lives in this space, for example• EMF from IBM, Corona from Microsoft

University of Utah SoC CS 6961 - Lecture 15 17

Metamodel Example

MultiplicityElement

Element

Namespace

TypedElement(from Basic)

MultiplicityElement(from Multiplicities)

Classi fier(from Super)

RedefinableElement(from Redefinitions)

Feature(from Classifiers)

StructuralFeature

StructuralFeature(from Changeabilities)

TypedElement

RedefinableElement

*

/redefinedElement

* {union}

Feature

Classi fier

*

/redefinitionContext

* {union}

*1..*

/feature

*{union,subsets member}

/featuringClassifier

1..* {union}

*

+general

*

TypedElement Type

0..1

type

0..1

Type(from Basic)

Type(from TypedElements)

TypedElement(from TypedElements)

NamedElement

NamedElement NamedElement

Type

University of Utah SoC CS 6961 - Lecture 15 18

Metamodel Example

• As you can see, the metamodel really isn’t fit for normal consumption– Certain parts of the metamodel are much

more complex than this– You have to learn how to “read the runes”

• However, the UML metamodel is the core what is legal and illegal UML– What can relate to what, what contains what,

the data, etc.

University of Utah SoC CS 6961 - Lecture 15 19

Metamodel Example 2

[0..1]

StructuralFeatureClassi fier

AggregationKind

nonesharedcomposite

<<enumeration>>

Relationship

[0..1]

Classi fier

Operation

Classi fier

ValueSpecification

Class

0..1 *

+class

0..1 {subsets namespace,subsets redefinitionContext}

+nestedClassifier

*{ordered, subsets ownedMember}

*

+/superClass

*{redefines general}

0..1 *

+class

0..1 {subsets redefinitionContext,subsets namespace,

subsets featuringClassifier}

+ownedOperation

*{ordered,subsets feature,

subsets ownedMember}

Property

isDerived : Boolean = falseisReadOnly : Boolean = falseisDerivedUnion : Boolean = false/ defaul t : Stringaggregation : AggregationKind = none/ isComposi te : Boolean

*

+redefinedProperty

*{subsets redefinedElement}

0..1

+/opposite

0..1

*

+subsettedProperty

*

0..1 *

+classifier

0..1 {subsets redefinitionContext}

+/attribute

*{union,subsets feature}

0..1 0..1

+owningProperty

0..1 {subsets owner}

+defaul tValue

0..1{subsets ownedElement}

0..1 *

+class

0..1 {subsets classifier,subsets namespace,

subsets featuringClassifier}

+ownedAttribute

*{ordered,subsets attribute,

subsets ownedMember}

Association

isDerived : Boolean = false

0..1*

+owningAssociation

0..1{subsets association,subsets namespace,

subsets featuringClassifier}

+ownedEnd

* {ordered,subsets memberEnd,

subsets feature,subsets ownedMember}

0..12..*

+association

0..1

+memberEnd

2..* {ordered,subsets member}

Type

1..*

+/endType

1..*

This is the basic UML class.

University of Utah SoC CS 6961 - Lecture 15 20

Metamodeling

• After seeing these models, I hope you feel a bit better about your class models– I mean, I could make you do this kind of thing.

• Really. I did it, so you can too… Right?

• Of course, these models aren’t example of “real-world models”– They have a very specific purpose.– “Real world” models much closer to code.

University of Utah SoC CS 6961 - Lecture 15 21

UML: Extensibility

• UML was built to be extended.

• For most people, it is enough to know that there is a thing called a “stereotype”– An a collection of stereotypes is a “profile”

• This should work for you as well– But UML can be extended in much more

powerful ways (tool support missing)

University of Utah SoC CS 6961 - Lecture 15 22

UML, DSMLs, Extensiblity

• Microsoft’s new initiative focuses on “Domain Specific Modeling Languages”– Part of Visual Studio 2005 modeling tools is a

toolkit for building new modeling languages– Codenamed Corona, now just part of VS 2005– Keep a eye on this (It’s really cool)– UML, Eclipse/Java community will get shaken

up by this, I think

University of Utah SoC CS 6961 - Lecture 15 23

UML Deconstructed

• Trust me when I say we can have a class just on the future of modeling, DSMLs, advanced model development…– Well, I hope so, because…

• It’s a planned seminar next semester (CS 7940-00x, TBA)– Prof. Kessler likely to be the official instructor

• I’ll be lucky to TA a 1000 level class after this…

University of Utah SoC CS 6961 - Lecture 15 24

UML Seminar

• Open to all that took this class– This includes seniors as well

• If you’ve never taken a seminar, I encourage it highly!

• Much different than this class– One credit hour: You must present a paper to

the class (Suggested papers will be available)– Three credit hours: Independent project

subject to my approval (limited to 2 students)

University of Utah SoC CS 6961 - Lecture 15 25

Coming Up

• An assortment of topics of interest to you– Or, pick your instructors brain.

• Again, if you have any other suggestions, let me know.– Also, look for HW5 this week!