Modelling Heuristics

http://verraes.net

“How do you approach software modelling problems?”
When a client asked me about my mental process, I didn’t have a proper answer — yet. The question intrigued me. Do you need a propensity for modelling, or is it a learnable skill? I embarked on a mission to find modelling heuristics: the mental tools, that help us look at the problem from different angles; the little tricks to validate a model before we build it; the rules of thumb that lead us to iteratively refine our solutions. In this talk, I share some of the ideas I collected from books, from people I interviewed, and from my own experiences.

--

Mathias Verraes is a recovering music composer turned programmer, consultant, blogger, and speaker. He advises companies on how to build enterprise web applications for complex business domains. For some weird reason, he enjoys working on large legacy projects: the kind where there’s half a million lines of spaghetti code, and nobody knows how to get the codebase under control. He’s the founder of the Domain-Driven Design Belgium community. When he’s not working, he’s at home in Kortrijk, Belgium, helping his two sons build crazy Lego train tracks.

Transcript

1. Modelling Heuristics @mathiasverraes
2. Mathias Verraes Independent Consultant Value Object Comm.V Student of Systems Meddler of Models Labourer of Legacy verraes.net
3. Is modelling a learnable skill?
4. The pain of a wrong abstraction
5. Upfront Model? 1 1 Scott W. Ambler, "Big Modeling Up Front (BMUF) Anti-Pattern", http://www.agilemodeling.com/ essays/bmuf.htm
6. You are always making mental models
7. Analysis model 2 vs Domain model 2 Martin Fowler, 1996, "Analysis Patterns: Reusable Object Models"
8. Heuristic Domain Language
9. Linguistic Relativism Sapir-Whorf Hypothesis 3,4 4 Paul Graham, "Beating the Averages", http://www.paulgraham.com/avg.html 3 Steven Pinker, 1994, "The Language Instinct"
10. Heuristic Find the Nouns Anti-pattern?
11. Heuristic Descriptive vs Influential Properties
12. [ { "licensePlate": "1-ABC-123", "brand": "BMW", "make": "X1", "color": "Aggregate Blue", ..., "location": "40.7127837,-74.0059413" }, ... ]
13. Heuristic Static / Dynamic
14. Heuristic Find the Verbs Commands
15. Verb-based: f = chain( breakTextIntoWords() : [String] groupWordsIntoLines() : [[String]] joinWordsInBrokenLines() : [String] joinBrokenLines() : String ) f("A long paragraph") -> "A long\nparagraph"
16. Noun-based: 7 f = chain( words() : [String] brokenLines() : [[String]] wordJoinedLines() : [String] joinedLines() : String ) f("A long paragraph") -> "A long\nparagraph" 7 Michael Feathers, "A Type Driven Approach to Functional Design", InfoQ
17. Heuristic Find the Sentences Find the Idioms
18. Heuristic Find the Scenarios
19. Given I have a product When I look at the price of a product ... or Given I have a product When I lookup the product in the pricing table ... ?
20. Remember, you are always making mental models
21. As a customer I want to ... Given there is a product When I look at the price of a product ... As a shop owner I want to ... Given I have a product When I lookup the product in the pricing table ...
22. Heuristic Actors and Roles
23. Heuristic The Worker and the Beneficiary
24. When I look at the price of a product ... When I lookup the product in the pricing table ...
25. Heuristic Segregating Reading and Writing
26. Heuristic Being Behaving Becoming Three B's 5 5 Gerald M. Weinberg, 1988, "Rethinking Systems Analysis and Design"
27. The customer sometimes has an email. Missing concept?
28. Heuristic Collaborative Construction6 Execution Tracking aka Planning/Execution/Analysis 6 Cyrille Martraire, "Collaborative Construction by Alberto Brandolini", http:// cyrille.martraire.com/2012/09/collaborative-construction-by-alberto-brandolini/
29. Heuristic Domain Events8 8 http://verraes.net/2014/11/domain-events/
30. Time ->
31. Heuristic Cause & Consequence
33. Cause & Consequence Human External system Process Time
34. Heuristic Business Rules Reasons for failure
36. Heuristic Consistency Boundary
39. Heuristic Entity Inclusion
41. Heuristic Temporal Expansion
43. Heuristic Temporal Shift
45. Heuristic Invariant Inclusion
47. Heuristic Conceptual Shift
49. Heuristic Crossing Streams
51. Heuristic Happy Path / Divergent Path9 9 Mathias Verraes, "Event Storming: on Fake Domains and Happy Paths", http://verraes.net/ 2014/07/event-storming-fake-domains-happy-paths/
52. Formal Informal Aformal
53. Throw Away the Model
54. @mathiasverraes verraes.net Workshops Domain-Driven Design verraes.net/workshops Ghent, Belgium, January 20-22 Newcastle, UK (TBC)