1. Informatics 121 Software Design I
Lecture 7 André van der Hoek
Duplication of course material for any commercial purpose without the explicit written permission of the professor is prohibited.
December 4, 2018 – 19:10:14
(c) 2007 University of California, Irvine – André van der Hoek

2. © 2007 University of California, Irvine – André van der Hoek
Today’s Lecture
System design
Essence of a design solution
Impromptu sketches
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

3. © 2007 University of California, Irvine – André van der Hoek
Informatics 121 View
System design
describes what the software system should do
“how does it fundamentally approach solving the problem?”
focuses more on desirability
typically represents an intermediate “design in progress”
typically captures the overall, essential framing of the solution
Implementation design
describes what the implementer should do
“how do we make the approach reality?”
focuses more on feasibility
typically represents a final “completed design”
typically captures a fully detailed roadmap
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

4. © 2007 University of California, Irvine – André van der Hoek
Informatics 121 View
A system design is
problem solving
aimed at customers, implementation designers, tester, and the system designer themselves
An implementation design is
creating a roadmap
aimed at programmers, testers, feedback to system designer
Both require creativity, flexibility and design
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

5. The Essence of a Design Solution – Where?
Structure
Context
Communication
User interface
Persistence
Algorithms
Naming
Interchange …
Internal data structures
Error handling
Distribution
Glue …
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

6. 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 in one or more suitable representations
These representations, in turn, each need to be specified in one or more appropriate languages
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

7. © 2007 University of California, Irvine – André van der Hoek
Structure
Why may the essence be found here?
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
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

8. © 2007 University of California, Irvine – André van der Hoek
Structure – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

9. Architecture – Examples
Not as formal, or even as informative, but helps people understand whats going on
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

10. © 2007 University of California, Irvine – André van der Hoek
Context
Why may the essence be found here?
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
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

11. © 2007 University of California, Irvine – André van der Hoek
Context – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

12. © 2007 University of California, Irvine – André van der Hoek
Context – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

13. © 2007 University of California, Irvine – André van der Hoek
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
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

14. Communication – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

15. Communication – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

16. Communication – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

17. © 2007 University of California, Irvine – André van der Hoek
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 paradigm?
what if the design concerns an e-commerce system? …
What may be a good design notation?
sketches
mock-ups
interaction scenarios
prototypes
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

18. User Interface – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

19. User Interface – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

20. © 2007 University of California, Irvine – André van der Hoek
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
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

21. Persistence – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

22. Persistence – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

23. © 2007 University of California, Irvine – André van der Hoek
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
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

24. © 2007 University of California, Irvine – André van der Hoek
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 }
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

25. © 2007 University of California, Irvine – André van der Hoek
Algorithms – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

26. © 2007 University of California, Irvine – André van der Hoek
Algorithms – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

27. © 2007 University of California, Irvine – André van der Hoek
Naming
Why may the essence be found here?
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
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

28. © 2007 University of California, Irvine – André van der Hoek
Naming – Examples
http: protocol
// separators
domain name
mens/ subdirectory name
shirts/ subdirectory name
formal.html document name (Web page)
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

29. © 2007 University of California, Irvine – André van der Hoek
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>>
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

30. © 2007 University of California, Irvine – André van der Hoek
Interchange
Why may the essence be found here?
what if the design concerns a manufacturer’s 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
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

31. Interchange – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

32. Interchange – Examples
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

33. The Essence of a Design Solution – Where?
Structure
Context
Communication
User interface
Persistence
Algorithms
Naming
Interchange …
Internal data structures
Error handling
Distribution
Glue …
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

34. Pocket Guide to System Design
Consider your goals and identify key concerns
what is at the heart of the system?
what do people (including you) need to understand about how this system will solve the problem being faced?
Choose design representations and languages 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?
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek

35. © 2007 University of California, Irvine – André van der Hoek
Design Studio I
Forthcoming in !
December 4, 2018 – 19:10:15
© 2007 University of California, Irvine – André van der Hoek