Practical_Domain-Driven_Design_-_A_Modeling_Exercise_NDC_Oslo_2026.pdf

Transcript

1. The most important question in software industry
2. Who is the User?
4. Who is the User?
5. When using a software product, in any moment, the users are…
6. The users are…. 1. Applying their own mental model of reality Solving business problems through software requires abstraction of reality Are you able to replicate that mental model while building the software product?
7. The users are…. 2. Exposed to constraints External constraints might cause user to interact with the system in unexpected ways Can you replicate the same constraints while building software product?
8. The users are…. 3. Operating within a context Context: The users have specific needs they are trying to fulfill in a particular moment Context changes over time
9. Who is the User? • Somebody solving a business problem through abstraction of reality • Somebody operating under a set of constraints • Somebody with specific needs
10. Who is the User? • Somebody with specific needs
11. Users vs. Software Products • Why do we keep on building systems with generic models of user’s needs?
12. Who is the User? Why is this “The Most Important Question in Software Industry”? Because…. this is why complex IT-systems fail!
13. The gap between specific needs and generic models • The users are expected to adapt to the system, not the other way around • The responsibility for fulfilling user needs is shifted to outside the system
14. The most important question in software industry “The hardest single part of building a software system is deciding precisely what to build.” (Fred Brooks, No Silver Bullet)
15. Practical Domain-Driven Design Modeling Exercise NDC Oslo 2026 Mufrid Krilic, Domain-Driven Design Coach CoWork, Norway
16. What can you expect to learn in the next 2 hours? Get comfortable with doing modeling in your context Do not settle at the first model!
17. What can you expect to learn in the next 2 hours? Do not settle at the first model!
18. What is a Model? «All Models are Wrong, but Some are Useful» - George Box
19. How does a model look like? • Conceptual model • Concepts and relationships
21. How does a model look like? • Formal model • With constraints in the modeling language
23. How does a model look like? • Code • The most formal model of them all
25. How does a model look like? • User Interface
27. How does a model look like? • Anything you prefer…. • My preference • Free-form modeling constructing visual sentences
29. Today’s challenge Understand the model of the business domain Model the product/system that solves the needs of the business domain
30. Bridge between problem and solutions space • Model is a language. • We need to speak the same language both in the problem space and solution space.
31. Detect the Boundaries! • Boundaries from different perspectives • • • • End-user Testing Product architecture Software architecture
32. Detect the Boundaries! • Boundary means multiple models! • • Test to see if multiple models could address end-user needs better Model is language • Watch out for language differences
33. Agenda When What 1020 About Modeling Part 1 Modeling by Functions/Tasks 15 minutes Exercise/Skill Builder Part 2 Modeling by Roles 15 minutes Exercise/Skill Builder Learn from each other – visit other groups 1120-1140 Break What happened in real-life story? Part 3 Modeling by Roles and Time 15 minutes Exercise/Skill Builder Part 4 Modeling by Capabilities 15 minutes Exercise/Skill Builder Learn from each other – visit other groups 1230 What happened in real-life story? Wrap-up  You are Here
34. Slides Available!
35. The real-life story…. The backdrop for the exercise
36. Domain: Healthcare – Patient Referrals ▪ Referral • Exchange of clinical information about the patient ▪ Communication between • Primary healthcare i.e. General Practitioner (GP) • Secondary healthcare i.e. hospitals • Including in-between hospitals
37. Domain use-cases: Referral Pathways ▪ Referral Reception: • Assigning to correct clinical expertise for referral assessment ▪ Referral Assessment: • Evaluating the clinical information in the referral sent from GP/referrer to decide on the most appropriate clinical pathway for the patient
38. Your role today: Product team! • Model a product/system that can help your client support referral process in a better way than with the existing system • Client: • Head of a moderate-size hospital in Norway • 14000 employees • 1 million patient appointments per year
39. What do we have at our hospital? • Legacy patient record system in production for many years • Many manual routines added to “keep the system afloat”
40. Referral Reception Patient is referred from primary care/GP for specialized treatment to secondary care/Hospital
41. Event Storming inspired notation Hot Spot
43. Referral Assessment Clinical evaluation on patient’s entitlement to specialist health care
45. You just showed us a model! • This was a model indeed! • • Model of problem space You will model solution space ☺
46. Different kinds of models As-Is To-Be • Model of the existing sociotechnical process • We want a new model for improved product/system support This was presented with Event Storming This is your task for today!
47. Modeling by Functions/Tasks Exercise 1
48. Functional Decomposition • Boundaries in the system follow the function that a user needs to do hers/his job • Classic approach • Boundary = Function
49. Model a product/system for Referral Pathway thus far • Build a model based on functions/tasks • Example of a function/task: Sending a letter to patient • Be clear about boundaries in the product/system • Test the model on the scenario in the problem space • If time
50. Agenda When What 1020 About Modeling Part 1 Modeling by Functions/Tasks 15 minutes Exercise/Skill Builder Part 2 Modeling by Roles 15 minutes Exercise/Skill Builder Learn from each other – visit other groups 1120-1140 Break What happened in real-life story? Part 3 Modeling by Roles and Time 15 minutes Exercise/Skill Builder Learn from each other – visit other groups Part 4 Modeling by Capabilities 15 minutes Exercise/Skill Builder 1230 What happened in real-life story? Wrap-up  You are Here
51. Event Storming extended notation Hot Spot
52. Referral Reception Patient is referred from primary care/GP for specialized treatment to secondary care/Hospital
54. Referral Assessment Clinical evaluation on patient’s entitlement to specialist health care
56. Modeling by Roles Exercise 2
57. Role-based decomposition • Boundaries in the system based on which roles perform different functions • Leads to more task-oriented model • Boundary = Role based function
58. Model a product/system for Referral Pathway thus far • Build a model based on roles added to the presented model • Example of a role: human and system actors • Be clear about boundaries in the product/system • Model boundaries around which roles perform different functions • Test your model on the scenarios from problem space • If time
59. Learn from each other! Visit other groups and exchange modeling approaches
60. Break 20 minutes! Product Development Coaching
61. Agenda When What 1020 About Modeling Part 1 Modeling by Functions/Tasks 15 minutes Exercise/Skill Builder Part 2 Modeling by Roles 15 minutes Exercise/Skill Builder Learn from each other – visit other groups 1120-1140 Break What happened in real-life story? Part 3 Modeling by Roles and Time 15 minutes Exercise/Skill Builder Learn from each other – visit other groups Part 4 Modeling by Capabilities 15 minutes Exercise/Skill Builder 1230 What happened in real-life story? Wrap-up  You are Here
62. Review Exercise 1 and 2 What happened in real-life story?
63. Referral Pathway Functions
64. Domain Model
65. Referral Pathway Role-based Decomposition
67. Who is the User?
68. Who is the user?
69. Who is the user?
70. Modeling by Roles and Time Exercise 3
72. Time- and role-based decomposition • Boundaries in the system based on which roles perform different function at different times • Supports context-oriented systems • Boundary = Role-based function in a user context
73. Model a product/system for Referral Pathway thus far • Build a model based on roles and time • Can you model Time explicitly? • Hint: What do you think happens first? Look at the Hot-Spots! • Be clear about boundaries in the product/system • Model boundaries around which roles perform different functions at different times • Test the model on the scenarios from the problem space • If time
74. Learn from each other! Visit other groups and exchange modeling approaches
75. Review Exercise 3 What happened in real-life story?
76. This was such a great question!
77. First-time Referral Assessment Inter-Hospital Referral In-Hospital Referral
80. Agenda When What 1020 About Modeling Part 1 Modeling by Functions/Tasks 15 minutes Exercise/Skill Builder Part 2 Modeling by Roles 15 minutes Exercise/Skill Builder Learn from each other – visit other groups 1120-1140 Break What happened in real-life story? Part 3 Modeling by Roles and Time 15 minutes Exercise/Skill Builder Learn from each other – visit other groups Part 4 Modeling by Capabilities 15 minutes Exercise/Skill Builder 1230 What happened in real-life story? Wrap-up  You are Here
81. Modeling by Capabilities Exercise 4
83. Regional Hospital Organization
84. Departments •Accident and Emergency Department •Anaesthesia and Surgical Services •Cancer Treatment and Medical Physics •Children and Youth Clinic •Clinical Nutrition •Communication •Department of Occupational Therapy •Dermatology •Emergency Clinic •Emergency Department Short Stay Unit •Finance •Haukeland hotel •Heart Disease •Human Resources •Internal Medicine •International Collaboration •Laboratory Medicine and Pathology •Maternity Ward •Medical Biochemistry and Pharmacology MBF •Medical Genetics •Neurology •Neurosurgery •Occupational Medicine •Occupational Outpatient Clinic •Ophthalmology •Oral Surgery •Orthopedic Clinic •Radiology department •Physiotherapy •Recruitment and Temporary Staffing Office •Psychiatry •Regional Centre for Asthma, Allergy and Other Hypersensitivity illnesses in Western Norway •Research and Development •Rheumatology •Secretariat for hospital management •Surgical Clinic •The Cancer Center for Education and rehabilitation- CCER •The Norwegian Arthritis Registry NorArthritis •The Norwegian Porphyria Centre NAPOS •Thoracic Medicine •Treatment abroad •Tuberculosis clinic •Women's Clinic
85. District Hospital Organization
86. • Emergency Department: • Acceptance of emergency aid (medical and surgical). • Internal Medicine Department: • Treatment of diseases of the internal organs, cardiovascular, and geriatrics. • Surgical Department: • General surgery, often focused on day surgery and planned procedures. • Maternity Ward / Birth center: • Services for pregnant women with expected normal births (some small hospitals only have midwife-led units). • Radiology / X-ray Department: • Image diagnostics such as CT, ultrasound and conventional x-ray. • Laboratory Medicine / Blood Bank: • Blood sample collection and analysis, including a blood bank in some places. • Anesthesia and Intensive Care Unit: • Handling of critically ill and pain management. • Ambulance Service: • Often closely linked to the hospital.
87. Decompositions by business capabilities • Boundaries in the system follow the capabilities that the business offers its’ customers • Boundary = Business Capability • • Boundary ≠ Function Model around the way the business is organized!
88. Model a product/system for Referral Pathway thus far • Build a model based on capabilities in the hospital • Hint: Look out for the differences in the working process • Hint: Look out how the hospital is organized • Be clear about boundaries in the product/system • Model boundaries around the purpose for the hospital
89. Review Exercise 4 What (should have) happened in real-life story?
91. Product Architecture Which users are we tailoring our products for? The cost of developing separate products for separate user groups The cost of customizing the product for diverse user groups
92. Software Architecture Aligning system boundaries with business intent Specific domain model highly aligned with needs of specific user groups Re-usable generic domain model that can be adapted to serve needs of multiple user groups
93. Wrap-up Where to go from here?
95. Core Domain • The thing that distinguishes you from the competitors • “Not every part of the system will be well-designed” • • Generic subdomain Supporting subdomain
96. Do not settle at the first model!
97. Practice! Start on Monday! Somewhere in safe environments then improve!
98. Thank You! Interested in mentoring on DDD and Software Architecture? Get in touch! • mufrid@cowork.no Helping Build Domain-Driven Product Organizations
100. Images • Vecteezy.com • Tim Hüfner • https://unsplash.com/@joshua_hoehne • https://unsplash.com/@kattyukawa • https://unsplash.com/@brett_jordan • https://unsplash.com/@andrewtneel • https://unsplash.com/@modestasu