Top-down or Bottom-up?

Transcription

1 Top-down or Bottom-up? Richard Kettelerij 1

2 Introduction Richard Kettelerij Software engineer Hands-on richardlog.com Apache committer 2

3 Overview Architectural approaches Case study Recap Questions 3

4 Characteristics Top-down Bottom-up 4

5 Characteristics Up-front Evolutionary 4

6 Characteristics Decomposition Up-front Composition Evolutionary 4

7 Characteristics Decomposition Up-front Composition Evolutionary Future Present 4

8 Characteristics Decomposition Up-front Evolutionary Future Composition Command & control Present Self-organizing 4

9 Decomposition Strategic vision Business goals IT principles Applications Technology Infra 5

10 Composition Strategic vision Business goals IT principles Applications Technology Infra 6

11 Mismatch Strategic vision Strategic vision Business goals Business goals IT principles IT principles Applications Applications Technology Technology Infra Infra 7

12 Recap Top-down - Up front - Decomposition - Start with future reqs. Bottom-up - Evolutionary / emergent - Composition - Start with present assets 8

13 Top-down Advantages - Executive sponsorship - Alignment with higher level goals - Enabler for large scale changes ( ) 9

14 Top-down Disadvantages - Analysis paralysis - YAGNI - Misalignment with existing IT 10

15 Bottom-up Advantages - Fast results, quick way to add value - Small steps, less likely to fail - Aligned with existing IT - Intrinsic motivation ( 11

16 Bottom-up Disadvantages - Risk no architecture - Less resources - Misalignment with long term strategy 12

17 Context Top-down - Waterfall process - (Traditional) enterprise Bottom-up - Agile process - System or application architecture architecture 13

18 Hypothesis When you re doing <type of architecture> using <type of process> you re likely to prefer <type of approach> 14

19 Hypothesis When you re doing enterprise architecture using waterfall you re likely to prefer a top-down approach 15

20 Hypothesis When you re doing application architecture using an agile process you re likely to prefer a bottom-up approach 16

21 Recap Both have pros and cons You probably have a preference 17

22 Middle-out Top Time Bottom 18

23 Case study 19

24 Case study Replacing a legacy administrative system for a semi-government organization Assignment: I/O 20

25 Case study Integration architecture But... project focused on CRM 21

26 Case study All interfaces should stay the same. Customer Hold on, why exactly? Architect 22

27 Influences Limited executive sponsorship High level goals were known SME Tight schedule 23

28 Approach Middle-out but largely bottom-up (evolutionary, composition) approach Starting... top-down with decomposition 24

29 Solution Batch vs. online processing 25

30 Solution Batch vs. online processing 25

31 Solution Batch vs. online processing 25

32 Results 60% interfaces unchanged 40% interfaces changed - 15% optimized - 15% redefined - 10% new 26

33 Results Rated **** (4 out of 5 stars) by Software Improvement Group On time 27

34 Results Reduced manual labor Information available faster 28

35 Results System gains visibility, new use cases emerge CRM? CRM KIP CRM KIP 29

36 Improvements Governance High availability (HA) - Failover 30

37 Recap & Questions 31

38 Recap You re comfortable with one approach Switch approaches from time to time Context is king 32

39 ? 33