Towards a UML Profile for Domain-driven Design of Microservice Architectures
- 1. Towards a UML Profile for Domain-driven Design of Microservice Architectures Microservices 2017 Florian Rademacher University of Applied Sciences and Arts Dortmund Institute for Digital Transformation of Application and Living Domains florian.rademacher@fh-dortmund.de October 25, 2017 – Odense, Denmark
- 2. Table of Contents 1 Introduction 2 Research Questions 3 Survey on UML Elements in Domain-driven Design 4 A UML Profile for Domain-driven Microservice Architecture Modeling 5 Conclusion and Future Work Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 1
- 3. Table of Contents 1 Introduction 2 Research Questions 3 Survey on UML Elements in Domain-driven Design 4 A UML Profile for Domain-driven Microservice Architecture Modeling 5 Conclusion and Future Work Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 2
- 4. The published Paper presentation of our paper “Towards a UML Profile for Domain-driven Design of Microservice Architectures” from this year’s Microservices: Science and Engineering Workshop (MSE@SEFM 2017) preprint available online (see the abstract at http://conf-micro.services for the link) Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 3
- 5. Domain-driven Design Domain-driven Design (DDD) set of model-driven practices, techniques and principles for software design primary design drivers: application domain, concepts and concept relationships selected core principles ... capturing of domain knowledge in domain models ... collaborative modeling of domain experts and software engineers (⇒ ubiquitous language) Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 4
- 6. Domain-driven Design Structural Domain Models selective abstractions of conceptual knowledge about a domain or relevant domain parts typically modeled as informal UML class diagrams with DDD patterns like Entity, Value Object, Aggregate, Repository role Cargo Aggregate * Customer Repository find by name(String) find by Customer ID(String) Cargo Repository find by Tracking ID(String) find by Customer ID(String) Delivery Specification Value Object arrival time Handling Event Entity completion time type Customer Entity name customer ID * * goal handled * Cargo Entity tracking ID Figure 1: Structural domain model with DDD patterns1 1 Evans, Domain-Driven Design, 2004. Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 5
- 7. Domain-driven Design and Microservice Architecture DDD and MSA2 1 identification of Bounded Contexts and shared Value Objects in domain models 2 mapping of Bounded Contexts and shared Value Objects to functional Microservices and interfaces role Cargo Bounded Context Customer Shared Value Object customer ID Customer Bounded Context Cargo Aggregate * Customer Repository find by name(String) find by Customer ID(String) Cargo Repository find by Tracking ID(String) find by Customer ID(String) Delivery Specification Value Object arrival time Handling Event Entity completion time type Customer Entity name customer ID «use» * * goal handled * Cargo Entity tracking ID Figure 2: Domain model with Bounded Contexts and shared Value Object 2 Newman, Building Microservices, 2015. Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 6
- 8. Domain-driven Design and Microservice Architecture Limitation: DDD is rather informal DDD patterns lack formal, UML-based foundation DDD patterns differ in notation ⇒ prevention of structured model operations like model transformation or semantic validation ⇒ decrease of models’ possible value Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 7
- 9. Table of Contents 1 Introduction 2 Research Questions 3 Survey on UML Elements in Domain-driven Design 4 A UML Profile for Domain-driven Microservice Architecture Modeling 5 Conclusion and Future Work Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 8
- 10. Research Questions RQ 1 Next to DDD patterns, which basic modeling constructs need to be supported for Domain-driven Microservice Architecture Modeling (DDMM)? RQ 2.1 How can UML’s profile mechanism be utilized to support DDMM? RQ 2.2 Which basic model transformations need to be supported for DDMM? Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 9
- 11. Table of Contents 1 Introduction 2 Research Questions 3 Survey on UML Elements in Domain-driven Design 4 A UML Profile for Domain-driven Microservice Architecture Modeling 5 Conclusion and Future Work Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 10
- 12. Survey on UML Elements in DDD Survey on UML Elements in DDD survey of 92 UML class diagrams3 representing real-world structural domain models results (UML-conform elements only): # Element Category Occurrence Count 1 Class Classes 92 (100%) 2 Attribute Attributes 72 (78.26%) 3 Multiplicity Multiplicities 67 (72.82%) 4 Non-navigable Association Associations 58 (63.04%) 5 Method Methods 49 (53.26%) 6 Unidirectional Navigable Association Associations 36 (39.13%) 7 Non-navigable Aggregation Associations 28 (30.43%) 8 “extends” Relationship (Inheritance) Associations 23 (25%) 9 Informal Constraint Constraints 13 (14.13%) 10 Unidirectional Navigable Aggregation Associations 11 (11.95%) 11 Formal Constraint Constraints 6 (6.52%) 12 Semi-formal Constraint Constraints 3 (3.26%) 13 Class Dependency Associations 2 (2.17%) Table 1: Results of surveying UML elements of structural domain models 3 from Evans, Domain-Driven Design, 2004. Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 11
- 13. Survey on UML Elements in DDD Survey on UML Elements in DDD survey of 92 UML class diagrams3 representing real-world structural domain models results (UML-conform elements only): # Element Category Occurrence Count 1 Class Classes 92 (100%) 2 Attribute Attributes 72 (78.26%) 3 Multiplicity Multiplicities 67 (72.82%) 4 Non-navigable Association Associations 58 (63.04%) 5 Method Methods 49 (53.26%) 6 Unidirectional Navigable Association Associations 36 (39.13%) 7 Non-navigable Aggregation Associations 28 (30.43%) 8 “extends” Relationship (Inheritance) Associations 23 (25%) 9 Informal Constraint Constraints 13 (14.13%) 10 Unidirectional Navigable Aggregation Associations 11 (11.95%) 11 Formal Constraint Constraints 6 (6.52%) 12 Semi-formal Constraint Constraints 3 (3.26%) 13 Class Dependency Associations 2 (2.17%) Table 1: Results of surveying UML elements of structural domain models 3 from Evans, Domain-Driven Design, 2004. Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 11
- 14. Survey on UML Elements in DDD Survey on UML Elements in DDD survey of 92 UML class diagrams3 representing real-world structural domain models results (UML-conform elements only): # Element Category Occurrence Count 1 Class Classes 92 (100%) 2 Attribute Attributes 72 (78.26%) 3 Multiplicity Multiplicities 67 (72.82%) 4 Non-navigable Association Associations 58 (63.04%) 5 Method Methods 49 (53.26%) 6 Unidirectional Navigable Association Associations 36 (39.13%) 7 Non-navigable Aggregation Associations 28 (30.43%) 8 “extends” Relationship (Inheritance) Associations 23 (25%) 9 Informal Constraint Constraints 13 (14.13%) 10 Unidirectional Navigable Aggregation Associations 11 (11.95%) 11 Formal Constraint Constraints 6 (6.52%) 12 Semi-formal Constraint Constraints 3 (3.26%) 13 Class Dependency Associations 2 (2.17%) Table 1: Results of surveying UML elements of structural domain models 3 from Evans, Domain-Driven Design, 2004. Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 11
- 15. Survey on UML Elements in DDD Survey on UML Elements in DDD survey of 92 UML class diagrams3 representing real-world structural domain models results (UML-conform elements only): # Element Category Occurrence Count 1 Class Classes 92 (100%) 2 Attribute Attributes 72 (78.26%) 3 Multiplicity Multiplicities 67 (72.82%) 4 Non-navigable Association Associations 58 (63.04%) 5 Method Methods 49 (53.26%) 6 Unidirectional Navigable Association Associations 36 (39.13%) 7 Non-navigable Aggregation Associations 28 (30.43%) 8 “extends” Relationship (Inheritance) Associations 23 (25%) 9 Informal Constraint Constraints 13 (14.13%) 10 Unidirectional Navigable Aggregation Associations 11 (11.95%) 11 Formal Constraint Constraints 6 (6.52%) 12 Semi-formal Constraint Constraints 3 (3.26%) 13 Class Dependency Associations 2 (2.17%) Table 1: Results of surveying UML elements of structural domain models 3 from Evans, Domain-Driven Design, 2004. Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 11
- 16. Survey on UML Elements in DDD Survey on UML Elements in DDD survey of 92 UML class diagrams3 representing real-world structural domain models results (UML-conform elements only): # Element Category Occurrence Count 1 Class Classes 92 (100%) 2 Attribute Attributes 72 (78.26%) 3 Multiplicity Multiplicities 67 (72.82%) 4 Non-navigable Association Associations 58 (63.04%) 5 Method Methods 49 (53.26%) 6 Unidirectional Navigable Association Associations 36 (39.13%) 7 Non-navigable Aggregation Associations 28 (30.43%) 8 “extends” Relationship (Inheritance) Associations 23 (25%) 9 Informal Constraint Constraints 13 (14.13%) 10 Unidirectional Navigable Aggregation Associations 11 (11.95%) 11 Formal Constraint Constraints 6 (6.52%) 12 Semi-formal Constraint Constraints 3 (3.26%) 13 Class Dependency Associations 2 (2.17%) Table 1: Results of surveying UML elements of structural domain models 3 from Evans, Domain-Driven Design, 2004. Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 11
- 17. Survey on UML Elements in DDD Survey on UML Elements in DDD survey of 92 UML class diagrams3 representing real-world structural domain models results (UML-conform elements only): # Element Category Occurrence Count 1 Class Classes 92 (100%) 2 Attribute Attributes 72 (78.26%) 3 Multiplicity Multiplicities 67 (72.82%) 4 Non-navigable Association Associations 58 (63.04%) 5 Method Methods 49 (53.26%) 6 Unidirectional Navigable Association Associations 36 (39.13%) 7 Non-navigable Aggregation Associations 28 (30.43%) 8 “extends” Relationship (Inheritance) Associations 23 (25%) 9 Informal Constraint Constraints 13 (14.13%) 10 Unidirectional Navigable Aggregation Associations 11 (11.95%) 11 Formal Constraint Constraints 6 (6.52%) 12 Semi-formal Constraint Constraints 3 (3.26%) 13 Class Dependency Associations 2 (2.17%) Table 1: Results of surveying UML elements of structural domain models 3 from Evans, Domain-Driven Design, 2004. Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 11
- 18. Table of Contents 1 Introduction 2 Research Questions 3 Survey on UML Elements in Domain-driven Design 4 A UML Profile for Domain-driven Microservice Architecture Modeling 5 Conclusion and Future Work Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 12
- 19. A UML Profile for Domain-driven MSA Modeling A UML Profile for Domain-driven MSA Modeling stereotypes for DDD patterns as extensions to UML metaclasses «Stereotype» Module «Stereotype» AggregatePart aggregateRoot : Class «Stereotype» AggregateRoot «Stereotype» BoundedContext «Metaclass» Package «Stereotype» Closure «Stereotype» SideEffectFree «Stereotype» ValidatesSpec «Stereotype» Spec «Stereotype» Repository «Stereotype» Entity «Stereotype» Service «Stereotype» DefinesIdentity «Stereotype» ValueObject immutable : Boolean «Metaclass» Property «Metaclass» Operation «Metaclass» Class Figure 3: The UML profile’s stereotypes for DDD patterns Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 13
- 20. A UML Profile for Domain-driven MSA Modeling A UML Profile for Domain-driven MSA Modeling OCL constraints to ensure intended usage of pattern stereotypes Stereotype Constraints based on UML Metamodel AggregatePart C1: Only Entities and Value Objects may be Aggregate parts C2: Assigned Aggregate root must have AggregateRoot stereotype C3: No incoming Associations from outside the Aggregate C4: Must be in same Bounded Context as Aggregate root AggregateRoot C5: Only Entities may be Aggregate roots C6: Aggregate must contain at least one part Entity C7: One Operation or at least one Property defines the identity Repository C8: Class has no other stereotypes C9: Class contains only Operations and at least one C10: Outgoing Associations must point to Entities or Value Objects DefinesIdentity C19: Must not be specification validation Operation C20: May only be applied within Entities BoundedContext C24: Must not have Module stereotype C25: Must not be nested, i.e. part of another Package Table 2: Selected stereotype constraints Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 14
- 21. A UML Profile for Domain-driven MSA Modeling Mapping profile-based models to MSA implementation determination of Microservice interfaces from Bounded Contexts on the basis of context associations associated context-external concepts or shared Value Objects as signature types DDD patterns Repository or Service for explicit interface operation definition open question 1: How to specify technical characteristics? open question 2: Which concrete operation of Repository or Service shall be used? open question 3: Which concrete shared Value Object shall be used? Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 15
- 22. Table of Contents 1 Introduction 2 Research Questions 3 Survey on UML Elements in Domain-driven Design 4 A UML Profile for Domain-driven Microservice Architecture Modeling 5 Conclusion and Future Work Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 16
- 23. Conclusion and Future Work Conclusion characterization of DDD by means of a literature survey with 92 structural domain models initial UML profile for DDMM Future Work main focus: implementation of model transformations for eventually deriving MSA code from profile-based models transformation of Bounded Contexts into services with deriving interfaces from context associations Florian Rademacher Towards a UML Profile for Domain-driven Design of MSAs 17