Presented at JAX London 2013 Agile methodologies have had us moving away from Big Up Front Design to evolutionary, emergent design. But how does that work in the real world? Using experiences gained when creating the new Java driver for MongoDB, Trisha takes us on a design journey, where the answer to every question is "It Depends", the users of the system and their use cases are unknown, and lurking at the back of every decision is the question “but will it be backwards compatible?” We’ve all been there, trying to work out how to implement requirements, but have we really thought about the process of design?

1. #JAXLondon
Design is a Process, not a
Document
Trisha Gee, Java Driver Developer
@trisha_gee
Tuesday, 29 October 13

2. Design: translate the
requirements in a
specification that describes
the global architecture and
the functionality of the
system.
http://homepages.cwi.nl/~paulk/patents/isnot/node4.html
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3. Managing the Development of Large
Software Systems - Dr Winston Royce
http://www.cs.umd.edu/class/spring2003/cmsc838p/Process/waterfall.pdf
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4. <This Page Left Intentionally Blank>
Agile Design
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5. Design is a Process, not
a Document
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6. The Problem
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7. Tuesday, 29 October 13

8. Tuesday, 29 October 13

9. Tuesday, 29 October 13

10. Tuesday, 29 October 13

11. Constraints:
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12. Backwards
Compatibility
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13. > What do you want
to do?
>_
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14. > What do you want
to do?
>_
Tuesday, 29 October 13

15. Design is a Process, not
a Document
Tuesday, 29 October 13

16. Bugs and
Defects
Unknown
Architecture
On Time and
Under Budget
New Features
Inconsistencies
Lack of
Experience
Tuesday, 29 October 13
Unclear
Objectives

17. Bugs and
Defects
Unknown
Architecture
On Time and
Under Budget
New Features
Inconsistencies
You Are Here
Lack of
Experience
Tuesday, 29 October 13
Unclear
Objectives

18. Bugs and
Defects
Unknown
Architecture
On Time and
Under Budget
New Features
Inconsistencies
You Are Here
Lack of
Experience
Tuesday, 29 October 13
Unclear
Objectives

19. Bugs and
Defects
...and here
New Features
Unknown
Architecture
...and here
On Time and
Under Budget
...and here
Inconsistencies
You Are Here
...and here
Unclear
Objectives
Lack of
Experience
...and here
Tuesday, 29 October 13

20. Bugs and
Defects
...and here
New Features
Unknown
Architecture
...and here
On Time and
Under Budget
...and here
Inconsistencies
You Are Here
...and here
Unclear
Objectives
Lack of
Experience
...and here
Tuesday, 29 October 13

21. Bugs and
Defects
...and here
New Features
Unknown
Architecture
...and here
On Time and
Under Budget
...and here
Inconsistencies
You Are Here
...and here
Unclear
Objectives
Lack of
Experience
...and here
Tuesday, 29 October 13

22. Bugs and
Defects
...and here
New Features
Unknown
Architecture
...and here
On Time and
Under Budget
...and here
Inconsistencies
You Are Here
...and here
Unclear
Objectives
Lack of
Experience
...and here
Tuesday, 29 October 13

23. Bugs and
Defects
...and here
New Features
Unknown
Architecture
...and here
On Time and
Under Budget
...and here
Inconsistencies
You Are Here
...and here
Unclear
Objectives
Lack of
Experience
...and here
Tuesday, 29 October 13

24. Bugs and
Defects
...and here
New Features
Unknown
Architecture
...and here
On Time and
Under Budget
...and here
Inconsistencies
You Are Here
...and here
Unclear
Objectives
Lack of
Experience
...and here
Tuesday, 29 October 13

25. Where do I start?
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26. > You are in a cluttered code base.
Everywhere you turn you see
different people’s styles.
> There are bugs to be fixed, and
new features that must be
implemented.
> Some users suggest improvements to
your product, others will kill you
if you change a thing.
> What do you want to do?
> _
Tuesday, 29 October 13

27. Maintainability
Spe
ed
Tes
tabi
lity
onsistency
C
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si
on
C
cy
ten
s
ability
Read
Im
mu
t
ab
il
ity

28. Design Goals
• Consistency
• Cleaner design
• Intuitive API
• Understandable Exceptions
• Test friendly
• Backwards compatible
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29. In The North Tower...
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30. Lack of consistency
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31. > What do you want
to do?
>_
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32. > What do you want
to do?
>_
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33. Why bother?
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34. Our Solution
• Static analysis
• Build tools
• Discipline
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35. Win!
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36. Meanwhile, in the East...
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37. Other adventurers!
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38. > What do you want
to do?
>_
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39. > What do you want
to do?
>_
Tuesday, 29 October 13

40. Our Solution
• Get them onboard
• Use the Scala driver as the guinea pig
• Give Morphia some love
• Talk to Spring
• Tests are your friends
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41. Lurking All Around...
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42. Backward Compatibility
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43. > What do you want
to do?
>_
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44. > What do you want
to do?
>_
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45. Our Solution
• An architecture
• Supports both APIs
• ...bonus of supporting other APIs too
• Tests tell us if we’ve done it right
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46. On the Southern Front
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47. The Public API
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48. > What do you want
to do?
>_
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49. > What do you want
to do?
>_
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50. Our Solution
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51. Our Solution
• Committees
• Documents / Spreadsheets
• Meetings
• Research
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52. Our Solution
• Committees
• Documents / Spreadsheets
• Meetings
• Research
• Hack Days
• Conferences
• Early Access
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53. Retrospective
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54. I wish...
• I had asked more questions.
• Particularly “why”
• I better understood my priorities
• We could use the whiteboard more
• I had focussed on tests even more
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55. Conclusion
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56. Tuesday, 29 October 13

57. Tools
Tuesday, 29 October 13

58. Your Inventory
• Your Technical Skills
• Your Domain Knowledge
• Your Life Experience
• Your Questions
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59. Environmental Inventory
• The Domain
• The People
• The Hardware
• Chosen Technology
• Existing Code / Application / Platform
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60. Your Inventory Grows
• Skills you learn
• Tools you research
• Team changes
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61. Some Examples
• Tests. Always a Good Thing
• Static Analysis
• An automated build
• Bug/feature tracker
• Visibility of WIP
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62. Design is a Process, not
a Document
Tuesday, 29 October 13

63. #JAXLondon
@trisha_gee
Questions
http://is.gd/java3mongodb
Tuesday, 29 October 13