The Architecture of a UML Virtual Machine

Transcription

1 The Architecture of a UML Virtual Machine Dirk Riehle dirk@riehle.org, Presented to Java User Group Switzerland, December 2003 Last updated. Copyright by Dirk Riehle. All rights reserved. Contact: dirk@riehle.org,

2 Motivation for UML Virtual Machines Immediate Feedback? no Prototyping Programming Environments Traditional Software Development yes UML Virtual Machines UML-Based Code Generation yes no Unified Design and Programming? Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 2of 22

3 Definition: UML Virtual Machine UML virtual machine Is an abstract computing machine (like any VM) Provides an instruction set and a memory model for representing objects Instruction set of a UML virtual machine Behavior modeled using UML itself, complemented by Java Elements are persistently represented using XMI Memory model of the virtual machine Memory management facilities of implementation language (Java) Dedicated packages, garbage collection Copyright 2001 by Dirk Riehle. All rights reserved. Contact: dirk@riehle.org, 3of 22

4 High-level Requirements for UML VM Model representation Represents models on all levels Model execution Interprets models for execution Causal connection between models Changes have immediate and defined effects Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 4of 22

5 UML 4-Layer Architecture (Logical Arch.) M3-level (MOF) M2-level (UML) M1-level (Domain Models) M0-level (User Objects) checking12345 checkingaccount checking765 metaclass class savingsaccount savings12345 foreigncurrencyaccount savings888 foreigncurrency98 datatype money Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 5of 22

6 Causal Connection Definition: Causal Connection A modeling level is causally connected with the next higher modeling level, if the lower level conforms to the higher level and if changes in the higher level lead to according changes in the lower level Consequences for UVM Immediate feedback to model changes Copyright 2001 by Dirk Riehle. All rights reserved. Contact: dirk@riehle.org, 6of 22

7 Single Causally Connected Model Modeling and Execution Environment checking12345 checkingaccount checking765 metaclass class savingsaccount savings12345 foreigncurrencyaccount savings888 foreigncurrency98 datatype money Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 7of 22

8 Java Implementation (Physical Arch.) MOF Impl. Classes UML Impl. Classes Gen. Impl. Classes ModelElement Element 0..* -instance Classifier MetaClass Class 1 -type Copyright 2001 by Dirk Riehle. All rights reserved. Contact: dirk@riehle.org, 8of 22

9 Mapping Logical/Physical Architecture 1 -type -instance 0..* MetaClass Class Element «technical instance» «technical instance» «technical instance» «technical instance» metaclass «logical instance» class «logical instance» checkingaccount «logical instance» checking12345 Copyright 2001 by Dirk Riehle. All rights reserved. Contact: dirk@riehle.org, 9of 22

10 Ensuring Causal Connection Every element has a reference to its class Every access to an element is type-checked by its class => Every M0-element is causally connected with its M1-class Every class is an element => Every Mn-element is causally connected with its Mn+1 class Copyright 2001 by Dirk Riehle. All rights reserved. Contact: dirk@riehle.org, 10 of 22

11 Element Functionality UML-derived functionality Generic attribute value and link access Type checking that can be switched on or off Handling of association objects VM-needed functionality Shallow/deep cloning, equality Backpointers, garbage collection Serialization, inspection Team collaboration state model, versioning External resource management Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 11 of 22

12 Behavior Modeling and Execution UML state machines State machines are most precisely defined Best understood how to implement OCL enhancements Ensure constraints and business rules Lightweight programming tasks Hand-programming (Java) Customization through policies Requires well-designed extension architecture Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 12 of 22

13 SKYVA Runtime Environment Predefined models with predefined implementations Technical as well as business models (some proprietary, some not) Includes configuration models Is paramount for efficient execution Transactions, persistence, security! Today: San Francisco; Soon: IBM Websphere Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 13 of 22

14 Project Experiences Use of UML virtual machine Low performance tasks only (e.g. system configuration) Underlies merged modeling and execution environment Use of code-generation approach For high-performance tasks (i.e., production system) Fully separated environments; different evolution strategies Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 14 of 22

15 Implementation Using keys rather than full-fledged runtime type-checking Keys only change if type information changes Keys speed up lookup Perfect hash function (lookup in array) Keys speed up type checking Keys carry type information Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 15 of 22

16 UML Simplifications No multi-valued attributes of elements Attributes of elements are always UML data type instances Only single inheritance between classes Only binary associations between classes Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 16 of 22

17 UML Enhancement: Application M2+ Category M1+ Category 0..* ModelElement Element 0..* -ownedelement -ownedelement -namespace Namespace Package -package Package Application Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 17 of 22

18 Open Issues Improve behavior modeling capabilities Integrate Action Semantics as Java replacement Improve execution speed Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 18 of 22

19 Bare-Bones UML Virtual Machines? Bare-bones UML Virtual Machine Knows only UML as basis for domain models Can only execute behavior of standard types of classes Does not allow for domain-specific UML extensions Advantages Easier to implement, better performance Disadvantages Forbids use of profiles in modeling Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 19 of 22

20 Missing Pieces 1/2 Element class Element/Class collaboration specification Behavioral specification of UML itself Time-honored tradition: eating your own dog food Operational model of VM Starting point (main) Life-cycle model (incl. garbage collection) Concurrency model Model evolution support Native call interface Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 20 of 22

21 Missing Pieces 2/2 Standardized technical models (libraries) GUI library Simple persistence Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 21 of 22

22 Summary Expect UML Virtual Machines Expect UML IDEs/systems like Smalltalk See Also see: yahoogroups.com/group/uml-virtual-machines If you have questions, feel free to If you (intend to) develop UML VMs Personal note: check out Copyright 2001 by Dirk Riehle. All rights reserved. Contact: 22 of 22