Practical Domain-Driven Design - Workshop at NDC 2025

If you are involved in almost any role related to software product development then you are, by definition, doing modeling. There is always a distinction between the real world and a software product, and the difference is in the model by which the software product chooses to describe the reality.

In this workshop you will practice modeling in order to become better at designing, organizing and building software products.

You will be guided to think from different perspectives and to produce multiple models for the same domain problem. We will cover four different modeling approaches, each bringing more nuance and detail in the understanding of the domain:

Functional decomposition
Role-based decomposition
Time- and role-based decomposition
Decomposition by business capabilities

The real-world problem from the domain of healthcare will be a foundation for the exercise.

Since product development is a cross-functional approach, this exercise will benefit from cross-functional mixture of participants. You are hereby encouraged to join the workshop, regardless of your role in software product development.

Transcript

1. Practical Domain-Driven Design Modeling Exercise NDC Oslo 2025 Mufrid Krilic, Domain-Driven Design Coach CoWork, Norway
2. What is the problem we are trying to solve?
3. We all do modeling…. We have no choice! A model is an abstraction of reality where we choose to keep the most relevant elements • The challenge is to be as explicit as possible about modeling • “the most relevant elements”
4. What will we cover in next 2 hours?
5. What can you expect to learn in next 2 hours? Get encouraged to practice modeling (even more) in your context Do not settle at the first model!
6. Storytelling with Models «All Models are Wrong but Some are Useful» - George Box
7. How does a model look like? • Conceptual model used for: • Product architecture • Domain model • System decomposition • User Journeys • Modeling language used for: • IT architecture • Code • User interface
13. Agenda When What 1020 About Modeling  You are Here 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
14. The real-life story…. The backdrop for the exercise
15. ▪ For patients with identical diagnoses sometimes the treatment has the best effect when done in a group of patients ▪ Examples: • Conversation therapy groups in psychiatry • Training sessions post-injury Domain: Healthcare - Group Therapy
16. Your role today: Product team! • Model a product/system that can help your client support group therapy 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
17. What is the current status at our hospital? • Legacy patient record system in production for many years • Group therapy functionality • Many manual routines added to “keep the system afloat”
18. ▪ Group Therapy: Setting up a group • Planning ▪ Group Therapy: Conducting group appointments • Check-in process Domain use-cases
19. Group Therapy Planning Somatic Department Rehabilitation after lifestyle affected diagnosis
26. Wait a minute! • Didn’t we just model something? • Yes! • Proving that modeling can be done in many ways
27. domainstorytelling.org domainstorytelling.org
28. Different kinds of models • Model of the existing socio- technical process for the group therapy As-Is • We want a new model for improved product/system support To-Be This was “As-Is” domain story This is the goal for today!
29. Modeling by Functions/Tasks Exercise 1
30. Functional Decomposition • Boundaries in the system follow the function that a user needs to do hers/his job • Classic approach • Boundary = Function
31. Model a product/system for Group Therapy thus far • Build a model based on functions/tasks in the domain story • Example of a function/task: Sending a letter to patient • Be clear about boundaries in the product/system • Model boundaries around functions
32. Agenda When What 1020 About Modeling Part 1 Modeling by Functions/Tasks 15 minutes Exercise/Skill Builder Part 2 Modeling by Roles  You are Here 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
33. ▪ Group Therapy: Setting up a group • Planning ▪ Group Therapy: Conducting group appointments • Check-in process Domain use-cases
34. Group Therapy Check-In Somatic Department Rehabilitation after lifestyle affected diagnosis
40. Modeling by Roles Exercise 2
41. Role-based decomposition • Boundaries in the system based on which roles perform different functions • Leads to more task-oriented model • Boundary = Role based function
42. Model a product/system for Group Therapy thus far • Build a model based on roles in the domain story • Example of a role: human and system actors • Be clear about boundaries in the product/system • Model boundaries around which roles perform different functions
43. Learn from each other! Visit other groups and exchange modeling approaches
44. Break 20 minutes! Product Development Coaching
45. 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?  You are Here 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
46. Review Exercise 1 and 2 What happened in real-life story?
47. Group Therapy Functions
48. Domain Model
49. Model of a “Group” • “Group” is defined as a set of properties needed to perform all the functions
50. Definition of a “Group” model • Physician and specialists • Patients • Appointments • Location/Venue • Patient attendance, including no-show • Patients exempted from payment • Invoice – preferred method • Diagnosis-based patient fee • Reference to § in law for compulsory interventions in psychiatry
52. Who is the user?
54. Role-based model “Group” planning context • Specialists • Patients • Appointments • Location • Reference to § in law for psychiatry “Group” check-in context • Patient attendance incl. no-show • Cancelled appointments • Patients exempted from payment • Invoice – preferred method • Diagnosis-based patient fee
55. Modeling by Roles and Time Exercise 3
56. 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
57. Model a product/system for Group Therapy thus far • Build a model based on roles and time in the domain story • Can you model Time explicitly? • Hint: Can activity ordering in domain story help? • Be clear about boundaries in the product/system • Model boundaries around which roles perform different functions at different times
58. Learn from each other! Visit other groups and exchange modeling approaches
59. Review Exercise 3 What happened in real-life story?
61. Who is the user?
63. Time- and role-based model “Group” planning context • Specialists • Patients • Appointments • Location • Reference to § in law for psychiatry “Group” check-in context • Patients exempted from payment • Invoice preferred method • Diagnosis-based patient fee “Group” billing context • Patient attendance, incl. no-show • Cancelled appointments
64. 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  You are Here 15 minutes Exercise/Skill Builder 1230 What happened in real-life story? Wrap-up
65. Agenda When What 1050 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 1150-1210 Break What happened in real-life story? Part 3 Modeling by Roles and Time 15 minutes Exercise/Skill Builder Part 4 Modeling by Capabilities  You are Here 15 minutes Exercise/Skill Builder Learn from each other – visit other groups 1300 What happened in real-life story? Wrap-up
66. Group Therapy Planning Psychiatric Department Adult Psychiatry
72. Modeling by Capabilities Exercise 4
73. Group Planning Somatic Department
74. Group Planning Psychiatric Department
75. 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 •Physiotherapy •Psychiatry •Radiology department •Recruitment and Temporary Staffing Office •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
76. 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!
77. Model a product/system for Group Therapy 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
78. Review Exercise 4 What happened in real-life story?
81. Model by Capabilities “Group” – psychiatry capability • Psychologist • Psychiatrist • Diagnosis • Reference to § in law • Patients • Appointments • Location for appointment outside hospital premises “Group” – medical clinical services • Physician • Diagnosis • Patients • Appointments
82. Wrap-up Where to go from here?
84. Core Domain • The thing that distinguishes you from the competitors • “Not every part of the system will be well-designed” • Generic subdomain • Supporting subdomain
85. Product Architecture Which users are we tailoring our products for? The cost of customizing the product for diverse user groups The cost of developing separate products for separate user groups
86. Software Architecture Aligning system boundaries with business intent Re-usable generic domain model that can be adapted to serve needs of multiple user groups Specific domain model highly aligned with needs of specific user groups
87. Do not settle at the first model!
88. Practice! Start on Monday! Somewhere in safe environments then improve!
89. Thank You! Get in touch for further study and more hints! • mufrid@cowork.no Helping Build Domain-Driven Product Organizations
91. Images • Vecteezy.com • Tim Hüfner • https://unsplash.com/@joshua_hoehne • https://unsplash.com/@kattyukawa • https://unsplash.com/@brett_jordan