Systems Modeling - utHe clicks on details, a window pops up showing the id 9928299, that this apartment is for sale, has 3 bedrooms [...] This is sometimes called user story, scenario

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Ulrich Norbisrath (http://ulno.net)University of Tartu

Systems Modeling, Fall 2009http://teaching.ulno.net

Systems Modeling

Lecture2009/29/09

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Outline

● Development methods and modeling● Concrete, abstract, example● Objects first development method● Story driven modeling● Final exercise

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Discussion about Programming Experience and Modeling

● Who likes to program?● Who likes to program in “real” projects (who

prefers just for fun)?● Who uses modeling in their development

environment (in “real” projects in fun projects)?

● Who likes to use modeling (private, work)?● What is wrong? / Is anything wrong?

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Models in the Development Process

● Team up with 3-4● Write down how you depict an ideal

development process and write down the use and importance of models and design documents in it (15 minutes)

● Report

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Concrete vs. Abstract

● Form teams of 3-4● Discuss and write down examples for

concrete and abstract things (10 examples).

● Create definitions of concrete, abstract, and example

● Write down two ideas, what this could have to do with modeling.

● Work on this for 15 minutes.● Report

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What is an example?● Concrete!● Wictionary (example):

– Something that is representative of all such things in a group.

– Something that serves to illustrate or explain a rule.– Something that serves as a pattern of behavior to be

imitated (a good example) or not to be imitated (a bad example).

– A parallel or closely similar case, especially when serving as a precedent or model.

– An instance (as a problem to be solved) serving to illustrate the rule or precept or to act as an exercise in the application of the rule.

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What role can examples play in software development?

● Documentation● Design documents● Models● Test cases● Mean to communicate with a customer● Analysis documents

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Example for an Example

Ralph Smith, 33 years old, investment banker for Goldman Sachs, wants relocate within London. He is currently in his private office at his apartment in London/Maidavale. He opens his Webbrowser and selects from his bookmarks inferato.com.

The initial webpage shows in the header: “You are currently located in London/Maidavale”. The left sidebar shows the categories “Housing, Events, Jobs, Other classifieds”. As Ralf has recently looked for buying a special electric guitar in the neighbourhood, the button “other classifieds” is pressed. He selects the Housing button, Other classifieds is automatically deselected and the first 10 search results show up. The first hit shows a description […]The second hit shows as description: “Nice quiet 3 bedroom apartment in Notting Hill with a perfect view and short ways to groceries and medical facilities.”He clicks on details, a window pops up showing the id 9928299, that this apartment is for sale, has 3 bedrooms [...]

This is sometimes calleduser story, scenario (a scenariois usually longer than auser story), business case, orseldom textual use case.

This is sometimes calleduser story, scenario (a scenariois usually longer than auser story), business case, orseldom textual use case.

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Scenario (our definition)● Very concrete story (assume the

development project already exists)● Long (half a page up to several pages)● Describing the system to develop● A case for things happening in and in

interaction with the system

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User Story (our definition)

● Very concrete example of the problem to solve (assume the development project already exists)

● Very short (less than half a page) – fits on a flash card

● Write down as:– Title– Pre condition– Action (<3 sentences)– Post condition

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Example, User Story

● Taken from user-story Wikipedia:Starting Application

The application begins by bringing up the last document the user was working with.

● Why does this not fit our definition?– Structure (no, pre- and post-condition)– Not concrete– => This is more a use-case

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Better Example for User Story

Title: Starting SuperTextEdit the second time

Precondition: SuperTextEdit has just been closed. The document mytext.txt had been edited by the user ulno and “Hello world!” had been written in it. Then SuperTextEdit had been closed and mytext.txt saved. SuperTextEdit is not running.

Action: SuperTextEdit is started again (approx. two minutes later) by user ulno on the same pc. mytext.txt is loaded and the main text-window of SuperTextEdit is displayed with mytext.txt as content.

Postcondition: SuperTextEdit is running and waits now for input and shows a blinking cursor at the end of the text.

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Towers of Hanoi

http://en.wikipedia.org/wiki/Towers_of_hanoi

Discs should be moved interactively.

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Create User Story“Move red disk to second place”

● Title: Move red disk to second place

● Teams● Write down User Story (10min)● Report

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User Story

● Title: Move red disk to second place● Precondition: red d. (size 1), yellow d. (size

2), blue d. (size 3), and orange disc (size 4) sorted on initial towerplace (of 3)

● Action: The player moves the red disc onto the second towerplace

● Postcondition: yellow, blue, and orange disc sorted on initial towerplace (of 3), red on second towerplace

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Use Cases and Use Case Diagrams

● Compile down with your neighbor a one page document, what the key elements of use cases, use case summary, and Use Case Diagrams are (10 minutes)

● Team up to teams with four and compile a one page document how you could relate user stories and use cases, create a use case summary for the Towers-of-Hanoi user story (10 minutes)

● Report

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Object

● A thing, being or concept ● A language mechanism for binding data

with methods that operate on that data● A representation of a physical object● Instance of a class● Objects represent “things” from the real

world, or from some problem domain

● How do objects and examples relate?

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Distinguishing Objects

● How can these be distinguished?– all persons in the world for the purpose of

sending mail– all persons in the world for the purpose of

criminal investigations– all customers with safe deposit boxes in a

given bank– all customers of a telephone company for

billing purposes– all employees of a company to restrict access

for security reasons

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Objects First Method

● Scenarios● User stories

– Tests– base for measurement

● Use cases● Object diagrams Class diagrams→● Story diagrams

● What is different to your dev. process?

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Modeling Objects

Red-Disc

size: 1


Yellow-Disc

size: 2

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Modeling Objects Relations/Interaction

Red-Disc

size: 1

Yellow-Disc

size: 2lies on

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User Story (revisited),how to identify objects?





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User Story,identify objects





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Model an Object Diagram

● Team● Object diagram for Move red disk, pre

condition (15min)– show change to post condition– what is special about this, what did you do for

this change?– how can we go from here to class diagrams?

● Report

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Object DiagramRed Disc

size: 1

Yellow Disc

size: 2

Blue Disc

size: 3

Orange Disc

size: 4

1st Towerplace 2nd Towerplace 3rd Towerplace

lies on top of

lies on top of

lies on top of

lies on top of

is next to is next to

Precondition for move red disc

Player

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Object DiagramRed Disc

size: 1

Yellow Disc

size: 2

Blue Disc

size: 3

Orange Disc

size: 4


lies on top of

lies on top of

lies on top of

lies on top of


Postconditionfor move reddisc

Player

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Object Diagram (revisited)Red Disc

size: 1

Yellow Disc

size: 2

Blue Disc

size: 3

Orange Disc

size: 4


lies on top of

lies on top of

lies on top of

lies on top of


Postconditionfor move reddisc

Player

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Class diagram

Playeromitted

upperlower

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Dynamic Object Browsing in Eclipse (eDobs) + Demo

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Story Diagrams

● Fujaba● Merge of State Diagrams, Activity Diagrams,

and Sequence Diagrams● Allow to visually model code via Graph

transformation of Object space

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Some Elements of Story Diagrams

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Some Elements of Story Diagrams

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Story Diagram in Code + Demo

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ExerciseConsider a computer email system● List three actors. Explain the relevance of

each actor.● Prepare a scenario● Break the scenario into small user stories● Draw the object diagrams for pre and post-

conditions● Derive use cases and sort user stories● Derive the class diagram● … SDM

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Summary

● Be able to decide when to be concrete or abstract

● Objects first● Story driven modeling

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Documents

Systems Modeling - utHe clicks on details, a window pops up showing the id 9928299, that this apartment is for sale, has 3 bedrooms [...] This is sometimes called user story, scenario