UML and WSDL
for JISC e-Learning Projects
INTRODUCTION TO UML
Richard Hopkins
rph@nesc.ac.uk
NeSC Training Team Member
Goals and Overview
Goals –
To enable you to understand the UML part of
the first example
To explain the context and overall approach
for UML
Overview
UML History and concepts
Simple use of most essential diagrams
 Requirements
 Structure
 Behaviour
JISC UML/WSDL – Introduction to UML, 16th Nov. 2004
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History of UML
Use of diagrams
In any discipline for the construction of complex
artefacts
Need to use diagrams, as tools for


Thinking
Communicating
As discipline matures, diagrams become 

Standardised –
For effective communication between all practitioners
Stylized –
Specialised technical language for compact representation
UML – M is for Models
A diagram is a model of the (proposed) system
A partial representation of some aspect of the system
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History of UML
Historically
A variety of stylised diagram languages
Each associated with a design methodology

A formalised Process for arriving at a design
E.g., for Object-oriented design (early 90’s)



Grady Booch’s OOD – Object-Oriented Design
James Rumbaugh’s OMT – Object-oriented Modelling and
Design
Ivar Jacobson’s OOSE – Object-Oriented Software Engineering
Competing Methodologies
Rather improbably –



Rumbaugh joined Booch, with intention of merging their
methods
They bought out Jacobsonn’s company – Objectory
These three aimed for a single Unified Method
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Methodolgy vs Notation
Generally need different methodologies for
different contexts
Small application in four weeks by single programmer
Large system in four years by 200-strong
development organisation
Often “use of X methodology” was actually
use of “X’s”notation
with methodology appropriate to context
Strong reasons for using the same notation
Concept of Unified Method, changed to Unified
Modelling Language
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Methodology vs Notation
UML is NOT a methodology
UML is a notation for recording the results of
A requirements gathering / design process
Carried out using some methodology – maybe!
Any kind of diagram can be used for any
purpose that is useful
Sufficiently general that could be used with
any imaginable O-O methodology
However, for concreteness we will assume a
particular general methodology JISC UML/WSDL – Introduction to UML, 16th Nov. 2004
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An Overall Development Process
Partially articulated
requirements
Capture
Requirements
Use Case Diag.
Construct
Model of
Overall system
Class Diag.
Sequence Diag.
Requirements
Structure
Behaviour
These diagram types, and the process can be used both for
Designing a new system
Understanding an existing system
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Requirements
Overview
UML History and concepts
Simple use of most essential diagrams
 Requirements
 Structure
 Behaviour
JISC UML/WSDL – Introduction to UML, 16th Nov. 2004
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Introducing the Library Example
A computer system for a university library; some “facts”
The library has members –
Staff
Students
The library contains items Books


possibly several copies of each book
Some books are for short-term loan only –
only students can do short-term loans
Journals

Only staff may borrow journals
The functionalities include
Keeping track of when items are borrowed/returned
Allow users to search for a book and check availability
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Some Queries
The library has members –
Staff
Students
Can someone be both?
The library contains
Do we mean copies?
Books;


possibly several copies of each book
Some books are for short-term loan only – only students can do shortterm loans
Journal

Only staff may borrow journals
The functionalities include
Keeping track of when items are borrowed/returned
Allow users to search for a book and check
availability
Is “user” something different from “member?
Henceforth use “user”
JISC UML/WSDL – Introduction to UML, 16th Nov. 2004
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Requirements Engineering
Natural language statement of
requirements is typically riddled with
ambiguities and inconsistencies
Requirements Engineering is the
discipline of dealing with this
Developing UML models helps with
identifying and clarifying requirements
But still depends on natural language
documentation
It helps, but does not guarantee
complete consistent set of requirements
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Requirements - Simple Use Cases
Borrow Copy
of book
Update
Catalogue
BookBorrower
Librarian
An Actor –
a user of the system, in a particular role
“BookBorrower” is a role played by library members
Usually a person, but could be another system
An entity outside the system being modelled
In web services – usually another web service
A Use Case –
A task that an actor needs to perform with the help of the
system
“Borrow Copy of Book” describes the successful outcome
– there will be variants for the exception cases This Actor participates in this Use Case
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Simple Use Cases
Use Case Documentation
Borrow Copy
of book
BookBorrower
Use Case: Borrow copy of book.
• A bookBorrower presents a book.
• The system checks that the potential
borrower is a member of the library,
• and that s/he does not already have the
maximum permitted number of books on loan.
Update
Catalogue
Librarian
• The maximum is 6 unless the member is is a
staff member, in which case it is 12.
• If both ckecks succeed, the system records
that this library member has this copy of the
book on loan.
• Otherwise it refuses the loan.
Not a very rich diagram – later on we will see richer diagrams
Needs more explanation – associated documentation
Limitations of natural language!
JISC UML/WSDL – Introduction to UML, 16th Nov. 2004
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STRUCTURE
Overview
UML History and concepts
Simple use of most essential diagrams
 Requirements
 Structure
 Behaviour
JISC UML/WSDL – Introduction to UML, 16th Nov. 2004
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Structure - Class Design
UML is for Object-Oriented Design
The state of the system is a collection of Objects
Each Object is an instance of a Class
The structure of the system is characterised by the
class and their inter-relationships
Key is identifying the classes
kinds of things manipulated within the system
Standard Technique - Noun identification
Take a concise description of the system
Identify the words/phrases that denote things
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Noun Identification
Some Facts –
The library contains books and journals.
It may have several copies of a given book.
The system must keep track of when items
are borrowed and returned
The system must allow users to borrow
items subject to rules –
 A student can borrow up to six items
…
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Class Design – Which Nouns?
Library
NO – Not “within the system”
System
Rule
Yes if rules are updatable
No if rules are built in
☺
Book
☺
Journal
☺
☺
☺
Yes –
All these are things which the system needs to track
Although they are not independent –
Journal is a special case of item
Student is a special case of user
Item
User
Student
Here a “book”, “student” etc. within the system –
Represents an actual entity in the external world
Partially Tracks what is happening to the real world
entity
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Class Diagram
User
Student
Student
Item
Staff
Journal
Book
A box for each Class
There are relationships between classes
Otherwise don’t need a diagram!!!
Specialisation/Generalisation
User is a generalisation of both
 Student
 Staff
Any instance of Student is also an instance of
User
Later we will see other class relationships
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Class Attributes and Operations
Item
Book
Title : String
Journal
Attribute – Information associated with each instance of the class –
what’s important for understanding;
not all that exists in a programming language class implementing it
Each attribute will have a type
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Class Attributes and Operations
Item
Book
Title : String
Journal
copiesOnShelf() : Integer
An operation – something that instances of this class can do,
which can be externally invoked
A unit of functionality which is externally exposed
Equivalent to a Java Method
copiesOnShelf() : Integer
To provide the invoker with a number which is the number of copies of
the book which are available for borrowing.
copies(in onShelf:Bool, out copyNos[0..*] Integer) : Status
UML terminology is message-passing An object’s operation is invoked by another object sending it a message
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Web Services as Objects
A WSDL definition corresponds to a class
“a service type”
An actual web service conforming to that
definition is an instance of that class
But service types are often not found by “noun
identification”
Often more by
Identifying Functions, rather than things



Legacy
Overall domain understanding (guesswork / intuition)
Notion of layered architecture
Viewing a function-provider as a service object
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Example some Web Services
A Web services Framework for E-learning (surprise!)
User Agents (layer)
Portal
Timetabling
Library
Authoring Tool
...
Application Service (layer)
Group Management
Resource Discovery
Resource Management
Common Services (layer)
Authentication
Authorisation
Search
Messaging
...
Naturally a domain noun? –
Yes
No
(As perceived by domain non-expert!)
JISC UML/WSDL – Introduction to UML, 16th Nov. 2004
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...
BEHAVIOUR
Overview
UML History and concepts
Simple use of most essential diagrams
 Requirements
 Structure
 Behaviour
JISC UML/WSDL – Introduction to UML, 16th Nov. 2004
23
Behaviour - Sequence Diagrams
To Document how objects work together to
achieve an overall function of the system –
An Interaction Diagram
Each sequence diagram shows an example
“walk-through”
Typically for a use case
Not for all of them
For


Complex situations
Where clarification seems needed
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Sequence Diagram - participants
For Use Case : Borrow copy of book
theUser: User
theCopy: Copy
theBook: Book
BookBorrower
Identify the participants
External Actor from the use case
Objects within the system
This is an instance diagram –
Name each object, and identify its class
theUser – object which is the internal representation of the
user playing the BookBorrower role
“theUser : User” seems redundant, but could have several
User participants
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Sequence Diagram – Lifelines
Book
Borrower
theUser: User
theCopy: Copy
theBook: Book
t
i
m
e
1:
2:
3:
4:
Object existence lifeline
Sending a message
Period of activation
The reply
1. BookBorrower invokes the use case – activating the corresponding User object,
theUser
2. theUser tells theCopy object that it is now borrowed – it changes its state
3. theCopy tells theBook that it has been borrowed – its reduces its count of
available copies
4. TheUser confirms success to BookBorrower
The replies to 2 and 3 not shown because not particularly important, whereas the
confirmation to external user is.
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Sequence Diagram – Operations
Book
Borrower
theUser: User
theCopy: Copy
theBook: Book
t
i
m
e
1: borrow(theCopy)
2: borrow()
3: borrowed()
4: borrowStatus
Sending a message
Object existence lifeline
Period of activation
The reply
Associate with the message line –
The information communicated
Usually the operation invoked and possibly its parameters
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Final Points
UML is a language to enable expression
Its up to you what you express and what you
don’t
Which cases you give sequence diagrams
Which attributes you include for a class
...
Based on maximising usefulness to the reader
Rather than rigid rules
But
it maybe you organisation’s standards,
rather than your personal judgement
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