1. Remarks on Software Design
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2. Today’s Lecture System design and implementation design System design
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3. Informatics 43 View Architecture design Module design
high-level partitioning of a software system into separate modules (components)
focus on the interactions among parts (connections)
focus on structural properties (architecture)
“How does it all fit together?”
Module design
detailed design of a component
focus on the internals of a component
focus on computational properties
“How does it work?”
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4. Informatics 121 View System design Implementation design
describes what the software system should do
focus towards addressing Goal and Domain of Use
“How do we fundamentally approach the problem?”
typically represents an intermediate “design in progress”
architecture design can be part of system design
Implementation design
describes what the implementer should do
focus towards addressing Domain of Materials
“How do we make the approach reality?”
typically represents a final “completed design”
module design can be part of implementation design
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5. Definitions A system design captures the essence of the solution
customers
system designers themselves
implementation designers
testers …
An implementation design captures the full solution
system designers
implementation designers themselves
programmers
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6. Implementation Design
Design Diamond
Domain of Materials
Domain of Use
Knowledge
Implementation Design
Representation
System Design
Ideas
Activity
concern
manipulates
informs
Goal
captures
enhances
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7. Design Diamond System Design Domain of Materials Domain of Use
Knowledge
Representation
System Design
Ideas
Activity
concern
manipulates
informs
Goal
captures
enhances
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8. Traditional View of System Design
architecture
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9. Traditional View of System Design
architecture
or...
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10. Traditional View of System Design
Statecharts
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11. Traditional View of System Design
Statecharts
or...
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12. Traditional View of System Design
UML
System Design
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13. Traditional View of System Design
UML
System Design
or...
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14. Traditional View of System Design
Data Flow Diagrams
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15. Traditional View of System Design
Data Flow Diagrams
or...
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16. Traditional View of System Design
Data Flow Diagrams
etc., etc., etc.
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17. Informatics 121 View of System Design
Booch …
pi calculus
informal drawing
UML
System Design
pseudo code
architecture
text
code
data flow diagrams
Statecharts
JSD
any and all as needed
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18. Design Concerns
A typical design problem consists of many different concerns that must all be addressed by a design solution
Some of these concerns are more important and/or have more impact than others
“I want my e-commerce site to have a recognizable logo” versus “My e-commerce site must scale to 1 million hits per minute”
Sometimes, the importance and/or impact of a concern is not obvious (the devil is in the details)
“I want my payroll software to properly handle the exchange rate”
As a designer, you need to find the concerns that are most important and have most impact
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19. Design Depth
Some concerns need to be designed in much greater depth than others
call control sequence of a cell phone versus the menu input mechanism of that same cell phone
This depth relates to
importance
impact
audience
This depth usually requires a rationale
As a designer, you need to work out each concern to the appropriate level of depth needed
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20. Design Depth Concern 1 Concern 2 Concern 3 Concern 4 Concern 5…
System “A”
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21. Design Depth Concern 11 Concern 12 Concern 13 Concern 14 Concern 15…
System “B”
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22. Design Depth Concern 21 Concern 22 Concern 23 Concern 24 Concern 25…
System “C”
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23. The Essence of a Design Solution – Where?
Structure
Context
Communication
User interface
Persistence
Algorithms
Naming
Interchange …
Internal data structures
Error handling
Distribution
Glue …
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24. The Essence of a Design Solution – Where?
Often, the essence is located in multiple places, related or unrelated
internal data structures and persistence
communication and protocols
user interface, persistence, and internal data structure
The essence usually constitutes a nucleus of concerns of high importance and high impact
The essence needs to be detailed at an appropriate depth
The essence needs to be captured in one or more appropriate design notations
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25. Structure Why may the essence be found here?
what if the design concerns a distributed application?
what if the design concerns a highly scalable application?
what if the design concerns a business application with highly changeable business rules? …
What may be a good design notation?
software architecture
UML2 component diagrams
simple drawings
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26. Structure – Examples
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27. Architecture – Examples
Not as formal, or even as informative, but helps people understand whats going on
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28. Context Why may the essence be found here?
what if the design concerns an integrated system constituting many existing systems?
what if the design concerns an application that will automate a significant portion of an organization’s business?
what if the design concerns an application spanning multiple businesses? …
What may be a good design notation?
context diagrams
informal drawings of external entities
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29. Context – Examples
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30. Context – Examples
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31. Communication Why may the essence be found here?
what if the design concerns a sensor network consisting of many different sensors emitting much different data?
what if the design concerns network quality of service?
what if the design concerns a broadcasting satellite?
what if the design concerns a document-centric system? …
What may be a good design notation?
labeled transition systems
UML sequence diagrams
data flow diagrams
protocols
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32. Communication – Examples
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33. Communication – Examples
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34. Communication – Examples
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35. User Interface Why may the essence be found here?
what if the design concerns real-time visualization?
what if the design concerns multiple kinds of displays?
what if the design concerns a drawing program?
what if the design concerns a new interaction mechanism?
what if the design concerns an e-commerce system? …
What may be a good design notation?
sketches
mock-ups
interaction scenarios
prototypes
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36. User Interface – Examples
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37. User Interface – Examples
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38. Persistence Why may the essence be found here?
what if the design concerns a database application?
what if the design concerns a system that must be fail safe?
what if the design concerns an application that must span multiple sessions? …
What may be a good design notation?
entity-relationship diagram
file format definition
UML class diagram
database schema
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39. Persistence – Examples
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40. Persistence – Examples
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41. Algorithms Why may the essence be found here?
what if the design concerns a search engine?
what if the design concerns encryption?
what if the design concerns a scheduling tool?
what if the design concerns a file converter? …
What may be a good design notation?
pseudo code
flow chart
Petri net
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42. Algorithms – Examples
public boolean moveRobot (Robot aRobot) {     //IF robot has no obstacle in front THEN         // Call Move robot         // Add the move command to the command history         // RETURN true     //ELSE         // RETURN false without moving the robot     //END IF }
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43. Algorithms – Examples
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44. Algorithms – Examples
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45. Naming Why may the essence be found here?
what if the design concerns a distributed system?
what if the design concerns replicated data?
what if the design concerns a complex set of interrelated data items? …
What may be a good design notation?
examples and counterexamples
regular expressions
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46. Naming – Examples http://www.clothes.com/mens/shirts/formal.html
http: protocol
// separators
domain name
mens/ subdirectory name
shirts/ subdirectory name
formal.html document name (Web page)
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47. Naming – Examples
D:/eclipse/edu/uci/isr/palantir/core/PalantirPlugin:1.2::.80c318ce.109c f96511d31371ce2.0::null
artifactID = filename:VID::wsID::parentID
parentID = artifactID | null
VID = [0-9.]*
wsID = [a-b0-9.]*
filename = <<continue with regular expression for pathnames>>
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48. Interchange Why may the essence be found here?
what if the design concerns a manufacturers supply chain management system?
what if the design concerns a credit report system?
what if the design concerns an airline booking system? …
What may be a good design notation?
ontology
data declarations
application programmer interface
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49. Interchange – Examples
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50. Interchange – Examples
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51. The Essence of a Design Solution – Where?
Structure
Context
Communication
User interface
Persistence
Algorithms
Naming
Interchange …
Internal data structures
Error handling
Distribution
Glue …
May 14, 2019 – 21:27:58

52. Informatics 121 View of System Design
Booch …
pi calculus
informal drawing
UML
System Design
pseudo code
architecture
text
code
data flow diagrams
Statecharts
JSD
any and all as needed
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53. Pocket Guide to System Design
Consider your goals and identify key issues
what is at the heart of the system?
what do people (including you) need to understand about this system?
Choose design notations that will help you explain these issues
what depth of understanding is needed?
what does your audience already know?
Remember to reflect on these representations as you progress
you will not have all the answers up front – change course as needed
This slide is by far not perfect. But I think something like it is needed?
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