Software Engineering Assignment 4


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SEG2105. Introduction to Software Engineering
Assignment 4 (2.5 %)

 You must use a software tool to draw the UML diagrams (VisualParadigm, LucidChart,
Umple, etc).
 You need to submit a report with all your answers. Don’t submit any tool-related files.
 Feel free to ask questions if you don’t understand the following system description or
write down your assumptions.
 Use the Discussion Board to ask questions related to this assignment.
 Do not leave this assignment to the last day; you would undoubtedly do badly if you
PART I (25 points)
A. [10 marks] E152 – b, c
B. [15 marks] Create a state diagram for the states of a specific flight. Refer to the
Airline example in the book, page 209.
The most common sequence is as follows: A flight starts in planned state. It is next assigned
a plane, and after that boarding starts when the captain declares the plane is ready for
passengers. After boarding is complete, the gate is closed and the captain awaits permission
to depart. The plane is then said to be ‘underway’. Upon arrival at the gate of the destination
airport, the flight is in ‘disembarking’ state until all the passengers are out. At that point the
flight is declared completed. However some other possible things can happen.
A flight can be underway, but never take off and be sent back to the terminal again (e.g. if
there is bad weather and the pilot is never given permission to take off). A flight can even
take off and then return to the original airport for some reason.
The flight can have more than one leg. In this case after passengers have got out, some
passengers may remain in the plane. When the crew is ready they will then let new
passengers board.
A flight can be cancelled in most states. However, if there are passengers on board, the
flight must ‘complete’ first, i.e. it must go to a gate and the passengers must all disembark
before it is declared cancelled.
Passengers may all be asked to leave the plane, even if it has not left the gate. This might
be because it is about to be cancelled, or because the airline needs to change the plane (e.g.
because a mechanical problem has been discovered).
The plane can be changed any time passengers are not on board (unless the flight is already
In extreme cases, passengers may be asked to leave the plane even if not at a gate (e.g. after
an emergency landing on the runway).
PART 2 (50 points)
A. [20 marks] Create a UML class diagram for the Decision-Making system described
below. Make sure you include correct multiplicity. Show all attributes and associations
plus at least five important operations. If generalizations are necessary, show them too.
Marks will be given for effort, even if you don’t have a perfect solution. However, marks
will be lost for the common types of mistakes we talked about in class (e.g. poor
generalizations, wrong multiplicity, etc).
B. [10 marks] Improve your class diagram by applying two of the patterns discussed in
Chapter 6. Describe only the changes to be made in your initial class diagram.
C. [20 marks] Design a state diagram describing the states a Decision instance can be in.
You must use the following states and events. Feel free to add more events and/or states,
if needed.
Initial state
 Under construction
Other non-final states
 On agenda (when it is ready to be considered and is on the agenda of one of the
 Under reconsideration (when a higher-level committee has not accepted it and has
pushed it back down to a lower level for further work)
Final states:
 FinalApproved (when approved by the highest-level committee that needs to
approve it)
 Rejected
 Dropped
 Split
 Put on agenda
 ApproveAndMove
 ApproveFinal
 ReturnToLowerLevel
 Reject
Many organization have decisions to make that are made by various committees in a hierarchical
manner. Committees exist at various levels. For example, there might be a departmental committee
that makes a decision, and passes the decision up to a division council for further approval, and
that then passes the result to the board of directors for final approval.
Some committees might consist of a single individual, e.g. a department head or director.
The system you will model needs to be able to handle any kind of organization; the committees or
individuals will have different names in each organization. In a university, for example, there
might be many levels: Department curriculum committee, department council, faculty curriculum
committee, faculty council, undergraduate council and Senate.
Decisions are of various types, with each type having an importance levels. Based on its
importance, a decision only needs to be approved up to a certain level in the hierarchy. For
example, the decision about which courses to offer in a given year might only need to be approved
by the department curriculum committee, but a new program of studies might need to be approved
by the Senate (and every level from department curriculum committee up to Senate). In a company,
an expense less than $1000 might need approval by a department head. Expenses of over $1000000
might need approval by the Board of Directors.
Each decision has a ‘short summary’ that describes the decision. Examples might be: ‘Purchase
Photocopier model AB309 from Xerox for $2570’ or ‘Create course SEG2107 with title: “Model
driven development”, and description: ‘Model driven development using Umple’, and
prerequisites: “SEG2105″‘
Short summaries can have multiple versions (as changes are made).
Each decision has associated with it a set of documents. Each document has an id, a filename, a
type (MS Word, Excel, Pdf etc.) and a set of versions.
When a committee approves a decision, it does so by approving the short summary, and possibly
modifying the set of documents by adding new versions of existing documents or adding new
A committee might turn down a decision based on one version of a document and request a list of
change requests that are simple blocks of text. Users or other committees may add comments to
the change requests and may create new versions of documents and an updated version of the short
summary. A decision may therefore go up the hierarchy, be rejected, come back down for
revisions, go back up again, back down again, and eventually be approved at the highest needed
level, or rejected or dropped at any level.
It is also possible for a committee to split a decision into separate decisions, or merge two decisions
together, or approve one decision conditional on approval of one or more other decisions.
Committees have members. Each member has a start and end date on the committee. Each
document has a set of authors. Each version has a date and a set of authors.

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