Mind Your Business ...and Its Logic

In spite of the myriad of technological advances we had over the past decades, the software industry is in a trouble: a huge percentage of projects fail to be delivered on-time, on-budget, and with the required quality. Are we missing something? Hell yes!

We build software to make our clients’ businesses more efficient. We do it by implementing the Business Logic, and it’s the cornerstone of all systems. Any malfunction in Business Logic undermines the very reason the system was built for. Yet despite its importance, this aspect of software engineering never got the spotlight it deserves. Time to fix this.

In this session you’ll get a toolbox for correctly implementing your system’s business logic:
* Overview of the major business domain modeling patterns
* A simple, yet strong heuristic for choosing a pattern that fits best your business domain
* Architectural ramifications of each pattern

Transcript

1. AND ITS LOGIC MIND YOUR BUSINESS
2. Vladik Khononov Chief Architect @ Internovus @vladikk http://vladikk.com
3. BUSINESS LOGIC
4. PRESENTATION LAYER BUSINESS LOGIC LAYER DATA ACCESS LAYER
6. PRESENTATION LAYER BUSINESS LOGIC LAYER DATA ACCESS LAYER
7. Transaction Script Active Record Domain Model Event Sourced Domain Model
8. TRANSACTION SCRIPT
9. TRANSACTION SCRIPT ▸ Simple Business Logic ▸ CRUD ▸ Input Validation ▸ Extract Transform Load (ETL) ▸ Simple Data Structures ▸ Always leave the database in a consistent state
10. 
 APPLICATION CREATE USER UPDATE USER SEARCH USERS DATABASE UI
11. public class CreateUser { public void Execute(name, email) { try { DB.StartTransaction();
 var row = DB.NewUserRow();
 row.Name = name;
 row.Email = email;
 DB.Append(row);
 DB.Commit(); } catch { DB.Rollback();
 throw; } } }
12. ACTIVE RECORD
13. ACTIVE RECORD ▸ Simple Business Logic ▸ CRUD ▸ Input Validation ▸ Extract Transform Load (ETL) ▸ Complex Data Structures ▸ References / Collections ▸ Multiple Tables
14. USER INTERESTS ID NAME Has
 many ADDRESS COUNTRY CITY STREET
15. 
 APPLICATION CREATE USER UPDATE USER SEARCH USERS DATABASE UI
16. 
 APPLICATION CREATE USER UPDATE USER SEARCH USERS UI 
 ACTIVE
 RECORDS USER DATABASE
17. public class CreateUser { public void Execute(userDetails) { try { DB.StartTransaction();
 
 var user = new User();
 user.Name = userDetails.Name;
 user.Email = userDetails.Email;
 user.Save();
 
 DB.Commit(); } catch { DB.Rollback();
 throw; } } }
18. public class User { public Guid Id { get; set; }
 public string Name { get; set; }
 public List<Interest> Interests { get; set; }
 public Address Address { get; set; } public void Save() { … }
 public void Delete() { … }
 public static User Get(Guid id) { … }
 public static List<User> GetAll() { … } }
19. DOMAIN MODEL
20. DOMAIN MODEL ▸ Complex Business Logic ▸ Business rules ▸ Invariants ▸ Calculations ▸ Complex algorithms
21. 
 APPLICATION CREATE USER UPDATE USER SEARCH USERS UI 
 ACTIVE
 RECORDS USER DATABASE
22. 
 APPLICATION CREATE USER UPDATE USER SEARCH USERS UI 
 DOMAIN
 MODEL USER DATABASE
23. 
 APPLICATION CREATE USER UPDATE USER SEARCH USERS UI 
 DOMAIN
 MODEL USER INFRASTRUCTURE
24. DOMAIN MODEL ▸ Complex business logic ▸ Model business domain ▸ Objects: data + behavior ▸ Plain objects ▸ Minimal application level use cases
25. public class UpdateUser { public void Execute(userDetails) { try { var user = usersRepository.Get(userDetails.Id);
 user.UpdateDetails(userDetails);
 usersRepository.Save(user); } catch { DB.Rollback();
 throw; } } }
26. public class User { public Guid Id { get; private set; }
 public string Name { get; private set; }
 public List<Interest> Interests { get; private set; }
 public Address Address { get; private set; } public void UpdateDetails() { … }
 public void AddInterest() { … }
 public static User InitializeNew() { … } } public interface IUsersRepository { User Get(Guid id);
 void Save(User user);
 void Delete(User user); }
27. 
 APPLICATION CREATE USER UPDATE USER SEARCH USERS UI 
 DOMAIN
 MODEL USER INFRASTRUCTURE
28. EVENT SOURCED
 DOMAIN MODEL
29. EVENT SOURCED DOMAIN MODEL ▸ Complex Business Logic ▸ Business rules ▸ Invariants ▸ Complex algorithms ▸ Deals w/ money ▸ Data analysis required ▸ Audit required by law
30. EVENT SOURCED DOMAIN MODEL Phone Email Name Id 46464543 one@gmail.com James 1 34234343 two@gmail.com John 2
31. public class NewUserInitialized { public Guid UserId { get; private set; }
 public string Name { get; private set; }
 public string Email { get; private set; } } public class NameChanged { public Guid UserId { get; private set; }
 public string NewName { get; private set; } } public class EmailChanged { public Guid UserId { get; private set; }
 public string NewEmail { get; private set; } }
32. EVENT SOURCED DOMAIN MODEL ▸ UserInitialized(1, John, john@gmail.com) ▸ NameChanged(1, James) ▸ EmailChanged(1, james@gmail.com)
33. 
 APPLICATION CREATE USER UPDATE USER SEARCH USERS UI 
 DOMAIN
 MODEL USER EVENT STORE
34. Transaction Script Active Record Domain Model Event Sourced Domain Model
35. APPLICATION ARCHITECTURE
36. LAYERED ARCHITECTURE PRESENTATION LAYER BUSINESS LOGIC LAYER DATA ACCESS LAYER
37. HEXAGONAL / PORTS & ADAPTERS / ONION / CLEAN ARCHITECTURE CORE SERVICES INFRASTRUCTURE
38. CQRS - COMMAND QUERY RESPONSIBILITY SEGREGATION WRITE MODEL COMMANDS UI READ MODEL QUERIES
39. «SHLIKHTA» ARCHITECTURE EVERYTHING
40. EVENT SOURCED DOMAIN MODEL • Shlikhta Architecture • Layered Architecture • Hexagonal Architecture • CQRS • Transaction Script • Active Record • Domain Model • Event Sourced Domain Model
41. TESTING STRATEGIES
42. TESTS PYRAMID UI
 /
 End to End Service / API
 layer tests Unit Tests
43. TESTS PYRAMID UI
 /
 End to End Service / API
 layer tests Unit Tests
44. TESTS PYRAMID UI
 /
 End to End Service / API
 layer tests Unit Tests
45. TESTS PYRAMID UI
 /
 End to End Service / API
 layer tests Unit Tests
46. TESTING STRATEGIES • End to end tests • API layer tests • Unit tests • Unit tests • Transaction Script • Active Record • Domain Model • Event Sourced Domain Model
47. LANGUAGE AND TECHNOLOGY
48. PROGRAMMING STYLE • Procedural • Procedural / OOP • OOP • Functional • Transaction Script • Active Record • Domain Model • Event Sourced Domain Model
49. DYNAMIC / STATIC TYPING • Dynamic • Dynamic • Static • Static • Transaction Script • Active Record • Domain Model • Event Sourced Domain Model
50. RAMIFICATIONS ▸ Architectural style / pattern ▸ Testing strategy ▸ Language and technology ▸ Programming style ▸ Language type
51. DECISION HEURISTIC ▸ Is the business logic mostly CRUD / ETL? Yes ▸ Are the data structures simple? yes - Transaction Script ▸ Are the data structures simple? No -Active Record ▸ Is the business logic mostly CRUD / ETL? No ▸ Is advanced analysis required, or dealing w/ money? No
 Domain Model ▸ Is advanced analysis required, or dealing w/ money? Yes
 Event Sourced Domain Model
52. TRANSACTION SCRIPT ACTIVE RECORD DOMAIN MODEL EVENT SOURCED DOMAIN MODEL
53. AGILE ARCHITECTURE
54. TRANSACTION SCRIPT / SHLIKHTA ACTIVE RECORD / LAYERS DOMAIN MODEL / HEXAGONAL EVENT SOURCED DOMAIN MODEL / CQRS
55. DECISION SCOPE
56. CAMPAIGN MANAGEMENT LEAD MANAGEMENT
57. 
 CAMPAIGN MANAGEMENT 
 LEAD MANAGEMENT CREATIVE CATALOG CAMPAIGN PUBLISHING BILLING USERS MANAGEMENT SALES COMMISSIONS CALCULATION DESK MANAGEMENT VOIP MANAGEMENT
58. SUMMARY
59. Business Driven Architecture
61. QUESTIONS?
62. THANK YOU Vladik Khononov Chief Architect @ Internovus @vladikk http://vladikk.com