EnergyEfficient Data Management for Sensor Networks

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M.Sc Computing Science Software Engineering
Lecture 3
Eli Katsiri Department of Computer Science and
Information Systems Birkbeck College, University
of London Email eli_at_dcs.bbk.ac.uk Web Page
http//www.dcs.bbk.ac.uk/eli
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Review of lecture 2

• The Unified Process provides a formal framework
  for defining requirements. How?
• Use-case model
• use cases and their diagrams
• system sequence diagrams (not introduced yet!)?
• 2. Vision
• 3. Supplementary specification
• 4. Glossary
• All artifacts start during Inception and are
  refined during Elaboration.

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Overview of lecture 3

• Moving from requirements to business modeling
  (analysis)?
• Domain Model
• Refining requirements based on feedback from
  analysis
• Contracts
• Moving from analysis to design
• An introduction to the Design Model
• Sequence diagrams
• Communication diagrams

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From requirements to business modeling

• Domain model
• the most important artifact of business modeling
• a visual representation of conceptual classes or
  real-world objects in a domain of interest
• not a visualization of software components
• Class diagrams (UML notation) show
• conceptual classes
• attributes of conceptual classes
• associations between conceptual classes
• Why do business modeling?

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A glimpse at a partial domain model
Sales LineItem quantity
Item
Records-sale-of
0..1
1
1..
Contained-in
1
Sale date time
Payment amount
Paid-by
1
1
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How to generate a domain model

• List candidate conceptual classes
• Draw them in a domain model
• Add associations for which information must be
  maintained
• Add the attributes necessary to fulfill the
  information requirements

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Conceptual classes

• Three ways of viewing a conceptual class
• Symbol
• Intension
• Extension
• In a domain model, we are interested in both the
  symbol and the intension of a conceptual class.

A sale represents the event of a purchase
transaction. It has a date and a time.
Sale date time
sale-1
sale-3
sale-2
sale-4
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How to identify conceptual classes
Use a conceptual class category list. -
physical objects - specifications, descriptions
- places - transactions - transaction line
items - roles of people - containers or
contained item - event - catalog etc.
Linguistic analysis Identify noun phrases in
the use cases. Process Sale Main Success
Scenario 1. Customer arrives at a POS checkout
with goods to purchase. 2. Cashier starts a new
sale. 3. Cashier enters item identifier. 4.
System records sale line item and presents item
description, price and total.
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Candidate Conceptual Classes
Product Catalog
Product Specification
Sales LineItem
Store
Item
Sale
Register
Manager
Payment
Customer
Cashier
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Some common mistakes
Why? Store should be a separate class A
specification or description class is needed
Improved object model
Sale store
Sale
Store
Item serial no description price prodId
Product Specification description price prodId
Item serial no
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How to identify associations

• An association is a relationship between object
  instances that indicates some meaningful and
  interesting connection
• worth remembering
• derived from the Common Associations List
• A is a physical (or logical) part of B
• A is physically (or logically) contained in
• A is a description of B
• A is known/captured/logged/recorded in B
• A uses or manages B
• A is related to a transaction B
• Etc.

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Candidate associations

• Relationships that need to be remembered
• Register Records Sale (why?)?
• Sale Paid-by Payment (why?)?
• ProductCatalog Records ProductSpecification
  (why?)?
• Relationships derived from the Common
  Associations List
• SalesLineItem Is-contained-in Sale
• Store Contains Item
• ProductSpecification Describes Item
• Cashier Is-member-of Store
• Cashier Uses/Manages Register
• Customer/Cashier Makes/Receives (Is-related-to)
  Payment
• Etc.

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Multiplicity of associations
T

Attention! The multiplicity value of a
relationship indicates how many object instances
can be validly associated with another, at a
particular moment, rather than over a span of
time.
1..
T
1..2
T
5
T
1,2,5
T
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Adding associations (names/multipl.)?
Product Catalog
Product Specification
SalesLineItem
Store
Item
Sale
Captured-on
Register
Manager
1
1
Cashier
Payment
Customer
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How to identify attributes

• Attributes in a domain model should preferably be
  simple attributes or data types
• Common types boolean, date, number, string,
  text, time
• Other types address, color, geometrics, phone
  number, national insurance number, universal
  product code, postal codes
• Do not relate conceptual classes with an
  attribute!
• Represent a data type as a non-primitive class
  if
• It is composed of separate sections
• Operations are associated with it (e.g. parsing)?
• It has other attributes
• It is an abstraction of one or more types (UPC,
  EAN)?

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More pitfalls
Why? prodID in class Item is a foreign key.
Foreign keys must not be added. amount is just a
number. Where is the currency?
Product Specification description prodID
Item serial no prodID
Describes
1

Payment amountNumber
Cashier nameString currentRegisterRegister
currentRegister is not a valid attribute. The
connection between Cashier and Register should be
denoted with a relationship
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Adding attributes
1
ProductCatalog

Contains
ProductSpecification
SalesLineItem quantity
1
1..
1
Used-by

Store
1..
Stocks
Item
Contained-in
1
0
1
Sale
Captured-on
Register
Manager
1
1
Started-by
1
1
1
1
1
Paid-by
Initiated-by
1
Records-sale-on
Cashier
Payment
Customer
1
1
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Overview of lecture 3

• Moving from requirements to business modeling
  (analysis)?
• Domain Model
• Refining requirements based on feedback from
  analysis
• Contracts
• Moving from analysis to design
• An introduction to the Design Model
• Sequence diagrams
• Collaboration diagrams

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From requirements and analysis to design
Process Sale
UP Use-case Model
Payment date time
Sale amount
Paid-by
UP Domain Model
1
1
Sale amount getBalance()Money
Payment date Time getTotal()Money
Paid-by
UP Design Model
1
1
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Design

• During object design, a logical solution based on
  the object-oriented paradigm is developed.
• The Design Model (main artifact) includes
• Interaction diagrams
• Class diagrams (next lecture)?
• Interaction and class diagrams are created in
  parallel.
• Notice
• Drawing interaction or class diagrams using
  correct UML notation is not the primary goal
  (intro in this lecture)
• The focus is to learn design skills (e.g.
  principles of responsibility assignment and
  design patterns) (next lecture)?

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Interaction diagrams

• Two kinds
• Communication diagrams
• Sequence diagrams
• Collaboration diagrams illustrate object
  interactions in a graph or network format, where
  objects can be placed anywhere in the diagram.
• Sequence diagrams illustrate object interactions
  in a fence format, in which each new object is
  successively added to the right.

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Interaction diagrams Why?
Communication diagram Sequence
diagram
msg1()?
ClassAInstance
ClassAInstance
ClassBInstance
1.msg2()?
msg1()?
2.msg3()?
msg2()?
ClassBInstance
msg3()?
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Code

• Public class A
• Private B myB new B()
• Public void msg1()?
• myB.msg2()
• myB.msg3()
• //

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Common interaction diagram notation

• Classes and instances
• class example
• instance examples
• Message expression syntax
• return message (parameterparameterType)
  returnType
• message example
• spec getProductSpec (idItemID) ProductSpec
• (type information can be omitted)?

Payment
p1Payment
Payment
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Sequence diagram notation

• Sequence is inferred by order of arrowed lines
  (top-bottom)?
• Activation boxes show message nesting
• Returns are illustrated with dotted lines

ClassAInstance
ClassBInstance
msg0()?
msg1()?
create()?
msg2()?
ClassCInstance
msg3()?
msg4()?
msg5()?
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C destructor
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Sequence diagram notation (cont.)?

• Conditional messages
• Mutually exclusive conditional messages
• Messages to class objects

ClassAInstance
ClassBInstance
ClassC
msg0()?
daySunday msg1()?
amountlt10 msg2()?
amountgt50 msg3()?
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Sequence diagram notation (cont.)?

• Iteration of a message
• Iteration of multiple messages
• Iteration over the items of a Collection object

CollClassInst
ClassAInstance
ClassBInstance
msg0()?
i1..N msg1()?
Loop(N)?
more items
msg2()?
msg3()?
i1..N
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Example NextGen POS
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Communication diagram notation

• Message number sequencing
• Message direction
• Creation messages
• Self messages

startSale()?
2.create(cashier)?
Register
Sale
1.clear()?
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Communication diagram notation (cont.)?

• Nesting of messages
• Conditional messages
• Mutually exclusive conditional paths

msg()?
1.msg1()?
ClassA
ClassB
1.1 cond1msg2()?
2.msg3()?
2bnot cond2.msg5()?
2acond2.msg4()?
ClassC
ClassD
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Communication diagram notation (cont.)?

• Iteration or looping
• Iteration over a collection
• Messages to a class, rather than an instance

ClassD
1.2 staticMsg()?
msg()?
1.msg1()?
ClassA
ClassB
1.1 i1..Nmsg2()?
2 msg3()?

CollectionClass
ClassC
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Summary of lecture 3

• We studied aspects of three disciplines in the
  Elaboration phase
• Within the Business Modeling discipline, we
  showed how the Domain Model (artifact) is used to
  represent visually the conceptual objects of our
  system.
• Within the Design discipline, we introduced
  interaction diagrams, and discussed notation for
  the two kinds of interaction diagrams
  communication and sequence diagrams.