This document discusses effective modeling when developing domain-driven designs (DDD). It emphasizes that the environment models are created in influences how they are developed. Effective modeling requires access to domain expertise, analysis and design, communication, and knowledge crunching. The document provides an example of modeling the appointment scheduling process for a hospital, starting from a naive view and refining the model through iterations as more questions are asked about the domain.

1. AMONGST MODELS
BY YVES REYNHOUT

2. ABOUT ME
A journeylist with a passion for well-designed, properly
decomposed, working software.
Professional experience: 20+ years, products, domains
such as Patient logistics, Real estate, Manufacturing,
Construction, Transportation, Oil & gas
Community experience: Occasional blogger about DDD,
CQRS & ES and Messaging, author of
and
Online presence: , ,
Company: , Belgium
AggregateSource
Projac
@yreynhout skype:yves.reynhout
mailto:yves.reynhout@gmail.com
BitTacklr BVBA

3. DISCLAIMER
90% of what you are about to hear, see, experience is
accurate.

4. WHAT IS DDD?

6. HOW DO MODELS
COME INTO
EXISTENCE?

7. The environment models are born into matters ...

8. Receptive or hostile?

9. Team size and Conway's law matter

10. Problem or solution?

11. Product or project?

12. Greenfield or brownfield?

13. Which slice in the strategic pie?

14. Birthing models requires effective modeling ...

15. EFFECTIVE MODELING MEANS
access to domain expertise
analysis & design
communicating & interviewing
brainstorming & experimenting
knowledge crunching
... continuously

16. EFFECTIVE MODELING MEANS
binding the model and the implementation
cultivating a language based on the model
developing & distilling a knowledge-rich model
... continuously

17. BUT DON'T TAKE MY WORD FOR IT ...

18. EXAMPLE?

19. AN APPOINTMENT RULES ENGINE
FOR HOSPITALS

21. SCHEDULING
Goal: to schedule appointments

22. How we perceive appointments in our daily life

24. Naive model

25. DR. JONES
performs give or take 20 appointments / day
works 200 days / year => 4.000 appointments per year
been working for 10 years => 40.000 appointments
oh dear, someone please suggest lazy loading or
snapshotting ...

26. WHAT ARE WE MISSING?
The most obvious things are often in plain sight ...

28. Revised Model

29. To bee or not to bee?

35. Revised Model

37. Revised Model

38. Revised Model

39. BUT ... WHERE DO SCHEDULE DAYS
COME FROM?

40. Bringing the hospital into the software

47. BUT ... HOW DO WE KNOW WHAT
CAN BE BOOKED ON A SCHEDULE
DAY?

55. BUT ... WHAT HAPPENS WHEN WE
CHANGE HOW A SCHEDULE DAY
WORKS?

56. Influences

57. Fairness

59. BUT ... MORE QUESTIONS HERE

60. SEARCH
Goal: to find the optimal slot

61. As seen by scheduling

62. As seen by search

66. BUT ... WHY BUILD A SEPARATE
MODEL FOR THAT?

72. BUT ... MORE QUESTIONS HERE

73. DECISION SUPPORT
Goal: to help find the right service

74. Simple model

75. LOOKING BACK

76. Q & A