The document discusses model-driven architecture and executable UML for code generation. It describes how translation-based processes using platform-independent models (PIMs) can generate platform-specific implementations (PSIs) automatically using mappings, avoiding manual coding and reducing maintenance costs compared to elaboration-based processes. The code generator itself is implemented as a set of domain models that embody rules for mapping PIM elements to target languages.

1. Welcome A Practical Guide to Code Generation using Model Driven Architecture and Executable UML 25 Jun 2008 Chris Raistrick, Kennedy Carter [email_address] KC.COM

3. Evolution or (Industrial) Revolution?

5. Elaboration Based Process The deliverables are up to 300% redundant… … and maintenance costs are correspondingly high Requirements (Text / Use Cases) This must be changed… or become obsolete This must be changed… or become obsolete This must be changed When this changes manually build a Platform Specific Model … PSM (UML) manually code a Platform Specific Implementation PSI (Ada/C++) manually build a Platform Independent Model … PIM (UML) Process definition Design policies Imp’n rules

6. Elaboration vs. Translation PSM (UML) Process definition Design policies Coding rules manually code a Platform Specific Implementation PSI (Ada/C++) manually build a Platform Independent Model … PIM (UML) Elaborate Translate manually build a Platform Specific Model … PSI (Ada/C/C++) automatically generate a Platform Specific Implementation using PIM-PSI mappings PIM-PSI Mappings (xUML) manually specify mappings onto the platform … manually build a Platform Independent Model … PIM (xUML) Requirement Change impact Technology Change impact

7. Translation Based Process Translate The knowledge in the heads of developers is: - Formalized - Accessible - Reusable - Refinable Process definition Design policies Coding rules PSI (Ada/C/C++) automatically generate a Platform Specific Implementation using PIM-PSI mappings PIM-PSI Mappings (xUML) manually specify mappings onto the platform … manually build a Platform Independent Model … PIM (xUML)

8. Formalized Application and Software Design Expertise PIM-PSI Mappings (xUML) automatically generate a Platform Specific Implementation using PIM-PSI mappings manually specify mappings onto the platform … manually build a Platform Independent Model … PIM (xUML) Rules and policies for organising aircraft Process definition Design policies Coding rules PSI (Code) Rules and policies for organising software

9. Platform Independent Modelling

11. The xUML Model Structure System Model Domains Classes Operations States xUML Model (PIM) Platform-Specific Configuration

13. Metamodel Based Code Generation

14. The Code Generator: Domains Populate Generate System Model Code Generator Generated Code xUML Runtime Layer Generated System Adaptation Layer The code generator itself is a set of domain models expressed using xUML. The domains represent the various components of an xUML system. (Part of) Code Generator Domain Chart xUML Model (PIM) Platform-Specific Configuration xUML-Code Mappings iCCG Code Generator

15. The Code Generator: Classes and Methods (Part of) Configurable Code Generator Domain Chart iCCG Code Generator Code Generator xUML-Code Mappings (Part of) Executable UML Class Model the classes in each domain represent the elements that make up those components. Method to Generate Java Method to Generate Ada Method to Generate C++ Method to Generate C … $FORMAT header_file typedef struct C[I:this.class_ID]_struct { /* "[T:this.class_name]" Class Header */ struct s_object *next_instance; $ENDFORMAT … Each element contains operations which specify how to map that xUML element onto a specific target language.

17. Instantiate the Formalism Metamodel Domain Instance Class Instances Attribute Instances Populated Executable UML Class Model When the Executable UML domain is populated with the PIM components, we see these instances… Populate xUML Model (PIM) Platform-Specific Configuration System Model xUML-Code Mappings iCCG Code Generator Code Generator

18. The Metamodels Embody the Code Generation Rules Domain.generateCode Class.generateCode Attribute.generateCode The task of translation involves iterating through these instances and generating suitable code from them. iCCG Code Generator Code Generator xUML-Code Mappings

19. Generate the Code Platform Independent Model : Class Diagram Generated C Code Generate Generate xUML-Code Mappings iCCG Code Generator Code Generator Generated Code xUML Runtime Layer Generated System Adaptation Layer

20. We have illustrated generation of data structures from the class model. The process of generating code from the action language is the same, and based upon populating and translating instances in the “Action Language” domain… Generating Code from Action Language Note that the “generateCode” operation of the “ASL Statement” class is polymorphic, allowing us to implement rival versions of this method for each type of ASL statement, represented as the subclasses “Create Statement”, “Delete Statement” and so on polymorphic operation with different polymorphic methods to generate code for each different ASL statement

21. Generate the Code Generator Project Code Generator Pre-Existing Code Generator Project Domain Models Project Code Code Generator PIM (part of) xUML Metamodel Domain Class Attribute xUML Metamodels xUML to Code Mappings in ASL

22. Code Generation Overview Populate Generate xUML Model (PIM) Platform-Specific Configuration System Model xUML-Code Mappings iCCG Code Generator Code Generator Generated Code xUML Runtime Layer Generated System Adaptation Layer PLATFORM SPECIFIC CONFIGURATION FILE PROCESS "Process One" ONE 1 127.0.0.1 1000 1600 PROCESS "Process Two" TWO 1 127.0.0.1 1001 1601 CLASS-PROCESS WM TGT ONE CLASS-PROCESS WM WPN TWO (part of) xUML Metamodel Domain Class Attribute owning_domain = this -> R2 $FORMAT header_file typedef struct D[I:owning_domain.domain_ID]_C[I:this.class_ID]_struct { /* "[T:this.class_name]" Class Header */ struct s_object *next_instance; /* Linked list of */ struct s_object *prev_instance; /* object instances */ struct s_object *rel_ptr; /* list of rel'ns */ struct s_object *cpr_ptr; /* list of cp rel'ns */ $ENDFORMAT {attributes_in_class} = this -> R3 for the_attribute in {attributes_in_class} do [] = ATT1:generateCode [header_file] on the_attribute endfor $FORMAT header_file }; $ENDFORMAT Multi-node multi-process runtime Windows Vista adaptation layer

23. Optimisation

28. Optimized Instance Handles The first element is a status indicator: 0 means “undefined”, 1 means “defined”. The second element (which is defined only if the first element is 1) is an index into the attribute arrays of the object it references, i.e. an object “pointer”. An instance handle can be realised as a 2-element array of integers. Instance attributes can be realised as fixed-length arrays, with a flag for each index to indicate whether that instance exists Customer custId custName custAddress

29. Optimized Associations note that creating and deleting objects and links does not involve any dynamic memory management… … even though there are ‘create’ and ‘delete’ statements in the PIM A binary association is implemented as two 2-dimensional arrays. Each array implements the association in one direction only. Customer End Account End Customer 0 owns Account 2 Account 6 is owned by Customer 2 accountId dateOpened balance ownerId status Account owns is owned by 1..* 0..1 R1 Customer custId custName custAddress

30. Generating Complex Architectures

33. Architecture Centric Metamodels {allNodes} = find-all Node for theNode in {allNodes} do {allProcesses} = theNode -> R2.Process for theProcess in {allProcesses} do [] = generateCode [] on theProcess endfor endfor UML Metamodel PIM Instantiate PSM Metamodel Define Mapping PSM Apply Mapping PSI Metamodel Define Mapping PSI Apply Mapping In architecture centric metamodels, the “generateCode” method iterates over the contents of the PSM (i.e. architecture) meta-models….

42. Portable Architectures

44. Runtime Metamodel Generated System This metamodel holds the PSM-PSI mappings Generated Code xUML Runtime Layer Adaptation Layer

46. Reuse of Mappings

47. MDA Limits the Impact of Business Rule and Technology Changes UML Metamodel Platform & implementation environment changes impact only here PIM Instantiate Business rule & requirement changes impact only here Manual or Automated PSM Metamodel Define Mapping PSM Apply Mapping PSI Metamodel Define Mapping PSI Apply Mapping

48. Reusable Mappings Are Defined at the Metamodel Level (part of) UML Metamodel Class Attribute Signal PSM Metamodel PSI Metamodel Define Mapping xUML Metamodel Define Mapping (part of) PSM Metamodel (object-based) Class PrivateDatum PublicMethod (part of) Ada 83 Metamodel Package BodyVariable SpecSubprogram

49. Reusable Mappings Are Defined at the Metamodel Level (part of) UML Metamodel Class Attribute Signal PSM Metamodel PSI Metamodel Define Mapping xUML Metamodel Define Mapping (part of) PSM Metamodel (object-based) Class PrivateDatum PublicMethod (part of) Java Metamodel Class Attribute Operation

52. The Code Structure Domain

53. Summary

55. Maintainability vs. Executability PSM (UML) manually build a Platform Specific Model … manually code a Platform Specific Implementation PSI (Code) manually build a Platform Independent Model … PIM (UML) Elaborate Compromise between maintainability and executability In classic approaches, the PSI (code) must be built to be maintainable, typically by incorporating layering and encapsulation … …which have a detrimental effect on speed and size of the executing system PSI (Code) automatically generate a Platform Specific Implementation using PIM-PSI mappings manually build a Platform Independent Model … PIM (xUML) Translate Built for executability Built for maintainability In translation-based approaches, the maintained entity (the PIM) is built for maintainability with layering and encapsulation… … while the executable entity (the PSI) is optimized for execution efficiency

56. The End A Practical Guide to Code Generation using Model Driven Architecture and Executable UML 25 Jun 2008 Chris Raistrick, Kennedy Carter [email_address] KC.COM