Dr. Maryam Kausar discusses object design, emphasizing its role in preparing for system implementation and ensuring efficiency in execution. The process involves four key activities: reuse of existing solutions, interface specification, object model restructuring, and optimization for performance. Emphasis is placed on component-based engineering to address design gaps and maintain proper relationships among objects using collections.

1. Object Design & Mapping
onto Code
By Dr. Maryam Kausar

2. Object Design
• Purpose of object design:
• Prepare for the implementation of the analysis model based on
system design decisions
• Transform analysis and system design models
• Investigate alternative ways to implement the analysis model
• Use design goals: minimize execution time, memory and other
measures of cost.
• Object Design serves as the basis of implementation
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3. Terminology: Naming of Design
Activities
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4. System Development as a Set of
Activities
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7. Object Design consists of 4
Activities
1. Reuse: Identification of existing solutions
• Use of inheritance
• Off-the-shelf components and additional solution objects
• Design patterns
2. Interface specification
• Describes precisely each class interface
3. Object model restructuring
• Transforms the object design model to improve its understandability and
extensibility
4. Object model optimization
• Transforms the object design model to address performance criteria such as
response time or memory utilization.
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10. One Way to do Object Design
• Identify the missing components in the design gap
• Make a build or buy decision to obtain the missing component
• => Component-Based Software Engineering:
• The design gap is filled with available components (“0 % coding”).
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12. Design to Code
Mapping
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13. Creating Class Definitions
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14. Creating Methods from
Interaction Diagrams
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15. Collections
• One-to-many relationships are common.
• For example, a Sale must maintain visibility to a group of many
SalesLineItem instances.
• In OO programming languages, these relationships are usually
implemented with the introduction of a collection object, such as
a List or Map, or even a simple array.
• Java libraries contain collection classes such as ArrayList and
HashMap, which implement the List and Map interfaces,
respectively.
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16. Collections
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17. Order of Implementation
• Classes need to be implemented from least-coupled to most-
coupled.
• E.g.,
• possible first classes to implement are either Payment or
ProductDescription;
• next are classes only dependent on the prior implementations—
ProductCatalog or SalesLineItem
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18. 1-18
SalesLineItem
quantity : Integer
getSubtotal()
ProductCatalog
...
getProductDesc(...)
ProductDescription
description : Text
price : Money
itemID : ItemID
...
Store
address : Address
name : Text
addSale(...)
Payment
amount : Money
...
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Register
...
endSale()
enterItem(...)
makeNewSale()
makePayment(...)
Sale
isComplete : Boolean
time : DateTime
becomeComplete()
makeLineItem(...)
makePayment(...)
getTotal()
...
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19. Activity
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