DOCSLIB.ORG

Typing and Subtyping of Metamodels

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Typing and Subtyping of Metamodels Typing and Subtyping of Metamodels Henning Berg and Birger Møller-Pedersen Department of Informatics, University of Oslo, Oslo, Norway Keywords: Metamodelling, Typing, Subtyping, Domain-specific Modelling, Languages. Abstract: In model-driven engineering, models are considered first-class entities. Model-driven engineering has been around for over a decade. Still, there has not been much work on how to type models or metamodels, which is important to realise true model-driven software development. In this paper, we discuss how a metamodel can be typed by means of an enclosing class whose state can be utilised by tools such as editors and interpreters. This allows using established object-oriented mechanisms on the metamodel level and supports specialisation of metamodels. 1 INTRODUCTION structure, software evolution and how to define func- tional model types. That is, model types whose defi- nition also cover behavioural semantics in addition to Model-Driven Engineering (MDE) (Kent, 2002) is structure. a collective term for a number of approaches and methodologies for software development in which The success of object-orientation is to a large ex- models are first-class entities. MDE can be seen as tent a consequence of its powerful mechanisms, e.g. a natural progression of object-orientation by rais- specialisation, polymorphism and composition (us- ing the abstraction level from the class level to the ing object references). The MDE philosophy sup- model level. A model is a set of interconnected ob- ports the idea that such mechanisms should also be jects, whose descriptions are formalised by a meta- available at the model and metamodel levels. Many model (class model). In spite of MDE’s model-centric mechanisms address these aspects of (meta)model us- view on software design and development, most MDE age and evolution, e.g. (Fabro et al., 2006)(Kolovos technologies and tools do not have native support for et al., 2006)(Groher and Voelter, 2007)(Fleurey et al., typing models or metamodels. This has consequences 2008)(Morin et al., 2009)(Morin et al., 2008). How- with respect to reuse of models, model transforma- ever, these mechanisms require the use of additional tions and interpreters. The notion of polymorphism at frameworks. Furthermore, composition and vari- the metamodel level is also unclear, as the type of a ability directives are described in separate resources metamodel is not well defined. The work of (Khne, (files) in the form of either a weaving model, point- 2010) motivates strongly why model substitutability cut model or composition/variability rules. Such ad- is a valuable property to aim for in MDE, whereas ditional resources complicate reuse. They also pose (Khne, 2006) discusses using inheritance, in the form certain challenges in maintaining files to reflect alter- of subtype specialisations, as a basic relationship be- ations of the metamodels. tween models. The notion of specialising (as in subtyping) meta- The work of (Steel and Jzquel, 2007) presents one models has not received the same attention as model approach for realising model typing in MDE. In par- transformations and composition. In this paper, we ticular, the work adresses concerns related to reuse of discuss how metamodels can be typed by nesting model transformations and interpreters, or in general, them within an enclosing class. We will see how the situations where externally defined code should be ap- enclosing class may indeed represent the type of the plicable to a number of different models all sharing enclosed metamodel. The enclosing class can be sub- a minimum set of properties as specified by a refer- typed which allows us to specialise metamodels. We ence model type. However, there are still many open will focus on metamodels whose behavioural seman- questions on how to support cases where model types tics is defined in methods or operations, as supported also cover behavioural semantics, and not just model by the Eclipse Modeling Framework (EMF) (Eclipse- Berg H. and Møller-pedersen B.. 111 Typing and Subtyping of Metamodels. DOI: 10.5220/0004713901110118 In Proceedings of the 2nd International Conference on Model-Driven Engineering and Software Development (MODELSWARD-2014), pages 111-118 ISBN: 978-989-758-007-9 Copyright c 2014 SCITEPRESS (Science and Technology Publications, Lda.) MODELSWARD2014-InternationalConferenceonModel-DrivenEngineeringandSoftwareDevelopment Foundation, 2013a), Kermeta (Muller et al., 2005) 2.1 Definitions and Example and Epsilon Object Language (EOL) (EclipseFoun- dation, 2013b). Definition 1. A metamodel type is an enclosing class The paper is organised in five main sections. Sec- containing an arbitrary number of non-static nested tion 2 discusses the basic mechanics of using class classes, attributes and operations. The nested classes nesting to type metamodels, and the purpose of typing constitute an EMOF-compatible metamodel. A meta- metamodels. Section 3 delves into the matter of using model type tm can be described as the sequence class nesting for defining metamodel types, whereas hname;c;a;oi · s, where c ⊂ C - a finite set of EMOF- Section 4 presents related work. Section 5 concludes compatible (nested) classes, a ⊂ A - a finite set of the paper. attributes (or references), o ⊂ O - a finite set of op- erations and s ⊂ T - a finite set of super metamodel types. 2 METAMODEL TYPES An example of a state machine metamodel type, named TStateMachine, is given below: A metamodel defined in the Essential MetaObject Fa- tm = hTStateMachine;fStateMachine; State; cility (EMOF) (OMG, 2013) architecture comprises Transition; Eventg;fsm : StateMachine; events : a set of classes contained in one or more packages, Eventg; ftransitionTable : Stringgi · nil whose objects constitute one or more models. The classes are related by association and specialisation Definition 2. A metamodel type instance is an object relationships (in the form of class properties). A of the class defining a metamodel type. The meta- metamodel can be uniquely identified by the name model classes of a metamodel type can be accessed and namespace of its containing package. However, a and instantiated via a metamodel type instance. Sev- package is not a semantically powerful concept (Mon- eral models can be created using the same instance. perrus et al., 2009), and can not be used as a type A metamodel type instance may have attributes (ac- specification for the contained metamodel. Specifi- cording to the metamodel type definition) whose val- cally, it is not clear how different packages relate and ues can be used to customise the metamodel. which operations that can globally be applied on the We will use Kermeta to illustrate the idea of meta- data (model objects) described by the package con- model types1. However, we will only use a subset of tents (classes). Kermeta to avoid complicating the picture. Kermeta A class specifies the type of its instances. The type is an object-oriented language for creating EMOF- is defined by the attributes and operations of the class. compatible metamodels. It allows specifying the be- In addition, non-static nested classes (inner classes) havioural semantics of metamodels within class oper- contribute to the type, as they can be considered class- ations. The operations are invoked at runtime when valued attributes. In this paper, we pursue the idea executing a model/program. We do not discuss static of defining a metamodel within an enclosing class. semantics (OCL) in this paper. The enclosing class is contained in a package. The Figure 1 gives the metamodel type TStateMachine purpose of defining a metamodel within an enclosing implemented in Kermeta syntax. The metamodel type class is that the class explicitly describes a type for the encloses a metamodel/language for modelling of state metamodel. Hence, using an enclosing class allows us machines. The metamodel comprises the four classes: to take advantage of established principles of object- StateMachine, State, Transition and Event. StateMachine orientation - at the metamodel level. The metamodel’s is the top node class of the metamodel from which type is that of the enclosing class. In the context of all other classes are reachable through relationships. this paper, we will simply refer to a class that encloses There is a reference typed with this class in the en- a metamodel as a metamodel type. A specific instance closing TStateMachine class. This reference is used to of a metamodel type represents a specific metamod- access the current model being processed by a tool el/language, and models of this metamodel/language (editor, interpreter, etc.). The metamodel details are will be in terms of objects of the classes enclosed in not of interest, therefore three consecutive dots are the specific instance. The instances of a given meta- used to represent content. model type will be generated by tools, while mod- As seen in Figure 1, the enclosing class has a ref- ellers will only be concerned with making models us- erence typed with the metamodel’s top node class. It ing the enclosed classes. also has a global operation named transitionTable() that 1Note that the current version of EMOF/Kermeta does not support nesting of classes as discussed in this paper. 112 TypingandSubtypingofMetamodels returns a textual description of all possible state tran- the general variant of the state machine metamodel sitions captured by a state machine model (i.e. the (tools e.g. editors will not be able to instantiate new model referenced by the sm reference). A step of the classes that have been added in subtypes). The exist- state machine is performed by invoking step(...) in the ing models of the initial state machine metamodel are State class. The step is carried out if the current state still valid, as changes and added properties are given has a transition whose event value is equal to the op- in the metamodel type variant. Existing tools may eration argument. then invoke redefined virtual operations in the nested classes of the metamodel subtype.
Load more

Recommended publications
  • An Extended Theory of Primitive Objects: First Order System Luigi Liquori
    An extended Theory of Primitive Objects: First order system Luigi Liquori To cite this version: Luigi Liquori. An extended Theory of Primitive Objects: First order system. ECOOP, Jun 1997, Jyvaskyla, Finland. pp.146-169, 10.1007/BFb0053378. hal-01154568 HAL Id: hal-01154568 https://hal.inria.fr/hal-01154568 Submitted on 22 May 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. An Extended Theory of Primitive Objects: First Order System Luigi Liquori ? Dip. Informatica, Universit`adi Torino, C.so Svizzera 185, I-10149 Torino, Italy e-mail: [email protected] Abstract. We investigate a first-order extension of the Theory of Prim- itive Objects of [5] that supports method extension in presence of object subsumption. Extension is the ability of modifying the behavior of an ob- ject by adding new methods (and inheriting the existing ones). Object subsumption allows to use objects with a bigger interface in a context expecting another object with a smaller interface. This extended calcu- lus has a sound type system which allows static detection of run-time errors such as message-not-understood, \width" subtyping and a typed equational theory on objects.
    [Show full text]
  • Metaobject Protocols: Why We Want Them and What Else They Can Do
    Metaobject protocols: Why we want them and what else they can do Gregor Kiczales, J.Michael Ashley, Luis Rodriguez, Amin Vahdat, and Daniel G. Bobrow Published in A. Paepcke, editor, Object-Oriented Programming: The CLOS Perspective, pages 101 ¾ 118. The MIT Press, Cambridge, MA, 1993. © Massachusetts Institute of Technology All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means (including photocopying, recording, or information storage and retrieval) without permission in writing from the publisher. Metaob ject Proto cols WhyWeWant Them and What Else They Can Do App ears in Object OrientedProgramming: The CLOS Perspective c Copyright 1993 MIT Press Gregor Kiczales, J. Michael Ashley, Luis Ro driguez, Amin Vahdat and Daniel G. Bobrow Original ly conceivedasaneat idea that could help solve problems in the design and implementation of CLOS, the metaobject protocol framework now appears to have applicability to a wide range of problems that come up in high-level languages. This chapter sketches this wider potential, by drawing an analogy to ordinary language design, by presenting some early design principles, and by presenting an overview of three new metaobject protcols we have designed that, respectively, control the semantics of Scheme, the compilation of Scheme, and the static paral lelization of Scheme programs. Intro duction The CLOS Metaob ject Proto col MOP was motivated by the tension b etween, what at the time, seemed liketwo con icting desires. The rst was to have a relatively small but p owerful language for doing ob ject-oriented programming in Lisp. The second was to satisfy what seemed to b e a large numb er of user demands, including: compatibility with previous languages, p erformance compara- ble to or b etter than previous implementations and extensibility to allow further exp erimentation with ob ject-oriented concepts see Chapter 2 for examples of directions in which ob ject-oriented techniques might b e pushed.
    [Show full text]
  • On Model Subtyping Cl´Ement Guy, Benoit Combemale, Steven Derrien, James Steel, Jean-Marc J´Ez´Equel
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by HAL-Rennes 1 On Model Subtyping Cl´ement Guy, Benoit Combemale, Steven Derrien, James Steel, Jean-Marc J´ez´equel To cite this version: Cl´ement Guy, Benoit Combemale, Steven Derrien, James Steel, Jean-Marc J´ez´equel.On Model Subtyping. ECMFA - 8th European Conference on Modelling Foundations and Applications, Jul 2012, Kgs. Lyngby, Denmark. 2012. <hal-00695034> HAL Id: hal-00695034 https://hal.inria.fr/hal-00695034 Submitted on 7 May 2012 HAL is a multi-disciplinary open access L'archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destin´eeau d´ep^otet `ala diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publi´esou non, lished or not. The documents may come from ´emanant des ´etablissements d'enseignement et de teaching and research institutions in France or recherche fran¸caisou ´etrangers,des laboratoires abroad, or from public or private research centers. publics ou priv´es. On Model Subtyping Clément Guy1, Benoit Combemale1, Steven Derrien1, Jim R. H. Steel2, and Jean-Marc Jézéquel1 1 University of Rennes1, IRISA/INRIA, France 2 University of Queensland, Australia Abstract. Various approaches have recently been proposed to ease the manipu- lation of models for specific purposes (e.g., automatic model adaptation or reuse of model transformations). Such approaches raise the need for a unified theory that would ease their combination, but would also outline the scope of what can be expected in terms of engineering to put model manipulation into action.
    [Show full text]
  • Common Lisp Object System Specification 3. Metaobject Protocol
    Common Lisp Object System Specification 3. Metaobject Protocol This document was written by Daniel G. Bobrow, Linda G. DeMichiel, Richard P. Gabriel, Sonya E. Keene, Gregor Kiczales, and David A. Moon. Contributors to this document include Patrick Dussud, Kenneth Kahn, Jim Kempf, Larry Masinter, Mark Stefik, Daniel L. Weinreb, and Jon L White. CONTENTS CONTENTS ................................................... ............ 3–2 Status of Document ................................................... ........... 3–5 Terminology ................................................... ................ 3–6 Introduction ................................................... ................ 3–7 Class Organization in the CLOS Kernel ............................................... 3–9 The Classes in the CLOS Kernel ................................................... 3–10 standard-class ................................................... ............ 3–11 forward-referenced-class ................................................... ..... 3–11 built-in-class ................................................... ............. 3–11 structure-class ................................................... ............ 3–12 funcallable-standard-class ................................................... .... 3–12 standard-slot-description ................................................... .... 3–12 standard-class-slot-description ................................................... 3–12 standard-method ................................................... .......... 3–12
    [Show full text]
  • Subtyping Recursive Types
    ACM Transactions on Programming Languages and Systems, 15(4), pp. 575-631, 1993. Subtyping Recursive Types Roberto M. Amadio1 Luca Cardelli CNRS-CRIN, Nancy DEC, Systems Research Center Abstract We investigate the interactions of subtyping and recursive types, in a simply typed λ-calculus. The two fundamental questions here are whether two (recursive) types are in the subtype relation, and whether a term has a type. To address the first question, we relate various definitions of type equivalence and subtyping that are induced by a model, an ordering on infinite trees, an algorithm, and a set of type rules. We show soundness and completeness between the rules, the algorithm, and the tree semantics. We also prove soundness and a restricted form of completeness for the model. To address the second question, we show that to every pair of types in the subtype relation we can associate a term whose denotation is the uniquely determined coercion map between the two types. Moreover, we derive an algorithm that, when given a term with implicit coercions, can infer its least type whenever possible. 1This author's work has been supported in part by Digital Equipment Corporation and in part by the Stanford-CNR Collaboration Project. Page 1 Contents 1. Introduction 1.1 Types 1.2 Subtypes 1.3 Equality of Recursive Types 1.4 Subtyping of Recursive Types 1.5 Algorithm outline 1.6 Formal development 2. A Simply Typed λ-calculus with Recursive Types 2.1 Types 2.2 Terms 2.3 Equations 3. Tree Ordering 3.1 Subtyping Non-recursive Types 3.2 Folding and Unfolding 3.3 Tree Expansion 3.4 Finite Approximations 4.
    [Show full text]
  • Balancing the Eulisp Metaobject Protocol
    Balancing the EuLisp Metaob ject Proto col x y x z Harry Bretthauer and Harley Davis and Jurgen Kopp and Keith Playford x German National Research Center for Computer Science GMD PO Box W Sankt Augustin FRG y ILOG SA avenue Gallieni Gentilly France z Department of Mathematical Sciences University of Bath Bath BA AY UK techniques which can b e used to solve them Op en questions Abstract and unsolved problems are presented to direct future work The challenge for the metaob ject proto col designer is to bal One of the main problems is to nd a b etter balance ance the conicting demands of eciency simplicity and b etween expressiveness and ease of use on the one hand extensibili ty It is imp ossible to know all desired extensions and eciency on the other in advance some of them will require greater functionality Since the authors of this pap er and other memb ers while others require greater eciency In addition the pro of the EuLisp committee have b een engaged in the design to col itself must b e suciently simple that it can b e fully and implementation of an ob ject system with a metaob ject do cumented and understo o d by those who need to use it proto col for EuLisp Padget and Nuyens intended This pap er presents a metaob ject proto col for EuLisp to correct some of the p erceived aws in CLOS to sim which provides expressiveness by a multileveled proto col plify it without losing any of its p ower and to provide the and achieves eciency by static semantics for predened means to more easily implement it eciently The current metaob
    [Show full text]
  • A Metaobject Protocol for Fault-Tolerant CORBA Applications
    A Metaobject Protocol for Fault-Tolerant CORBA Applications Marc-Olivier Killijian*, Jean-Charles Fabre*, Juan-Carlos Ruiz-Garcia*, Shigeru Chiba** *LAAS-CNRS, 7 Avenue du Colonel Roche **Institute of Information Science and 31077 Toulouse cedex, France Electronics, University of Tsukuba, Tennodai, Tsukuba, Ibaraki 305-8573, Japan Abstract The corner stone of a fault-tolerant reflective The use of metalevel architectures for the architecture is the MOP. We thus propose a special implementation of fault-tolerant systems is today very purpose MOP to address the problems of general-purpose appealing. Nevertheless, all such fault-tolerant systems ones. We show that compile-time reflection is a good have used a general-purpose metaobject protocol (MOP) approach for developing a specialized runtime MOP. or are based on restricted reflective features of some The definition and the implementation of an object-oriented language. According to our past appropriate runtime metaobject protocol for implementing experience, we define in this paper a suitable metaobject fault tolerance into CORBA applications is the main protocol, called FT-MOP for building fault-tolerant contribution of the work reported in this paper. This systems. We explain how to realize a specialized runtime MOP, called FT-MOP (Fault Tolerance - MetaObject MOP using compile-time reflection. This MOP is CORBA Protocol), is sufficiently general to be used for other aims compliant: it enables the execution and the state evolution (mobility, adaptability, migration, security). FT-MOP of CORBA objects to be controlled and enables the fault provides a mean to attach dynamically fault tolerance tolerance metalevel to be developed as CORBA software. strategies to CORBA objects as CORBA metaobjects, enabling thus these strategies to be implemented as 1 .
    [Show full text]
  • 13 Templates-Generics.Pdf
    CS 242 2012 Generic programming in OO Languages Reading Text: Sections 9.4.1 and 9.4.3 J Koskinen, Metaprogramming in C++, Sections 2 – 5 Gilad Bracha, Generics in the Java Programming Language Questions • If subtyping and inheritance are so great, why do we need type parameterization in object- oriented languages? • The great polymorphism debate – Subtype polymorphism • Apply f(Object x) to any y : C <: Object – Parametric polymorphism • Apply generic <T> f(T x) to any y : C Do these serve similar or different purposes? Outline • C++ Templates – Polymorphism vs Overloading – C++ Template specialization – Example: Standard Template Library (STL) – C++ Template metaprogramming • Java Generics – Subtyping versus generics – Static type checking for generics – Implementation of Java generics Polymorphism vs Overloading • Parametric polymorphism – Single algorithm may be given many types – Type variable may be replaced by any type – f :: tt => f :: IntInt, f :: BoolBool, ... • Overloading – A single symbol may refer to more than one algorithm – Each algorithm may have different type – Choice of algorithm determined by type context – Types of symbol may be arbitrarily different – + has types int*intint, real*realreal, ... Polymorphism: Haskell vs C++ • Haskell polymorphic function – Declarations (generally) require no type information – Type inference uses type variables – Type inference substitutes for variables as needed to instantiate polymorphic code • C++ function template – Programmer declares argument, result types of fctns – Programmers
    [Show full text]
  • On the Interaction of Object-Oriented Design Patterns and Programming
    On the Interaction of Object-Oriented Design Patterns and Programming Languages Gerald Baumgartner∗ Konstantin L¨aufer∗∗ Vincent F. Russo∗∗∗ ∗ Department of Computer and Information Science The Ohio State University 395 Dreese Lab., 2015 Neil Ave. Columbus, OH 43210–1277, USA [email protected] ∗∗ Department of Mathematical and Computer Sciences Loyola University Chicago 6525 N. Sheridan Rd. Chicago, IL 60626, USA [email protected] ∗∗∗ Lycos, Inc. 400–2 Totten Pond Rd. Waltham, MA 02154, USA [email protected] February 29, 1996 Abstract Design patterns are distilled from many real systems to catalog common programming practice. However, some object-oriented design patterns are distorted or overly complicated because of the lack of supporting programming language constructs or mechanisms. For this paper, we have analyzed several published design patterns looking for idiomatic ways of working around constraints of the implemen- tation language. From this analysis, we lay a groundwork of general-purpose language constructs and mechanisms that, if provided by a statically typed, object-oriented language, would better support the arXiv:1905.13674v1 [cs.PL] 31 May 2019 implementation of design patterns and, transitively, benefit the construction of many real systems. In particular, our catalog of language constructs includes subtyping separate from inheritance, lexically scoped closure objects independent of classes, and multimethod dispatch. The proposed constructs and mechanisms are not radically new, but rather are adopted from a variety of languages and programming language research and combined in a new, orthogonal manner. We argue that by describing design pat- terns in terms of the proposed constructs and mechanisms, pattern descriptions become simpler and, therefore, accessible to a larger number of language communities.
    [Show full text]
  • A Core Calculus of Metaclasses
    A Core Calculus of Metaclasses Sam Tobin-Hochstadt Eric Allen Northeastern University Sun Microsystems Laboratories [email protected] [email protected] Abstract see the problem, consider a system with a class Eagle and Metaclasses provide a useful mechanism for abstraction in an instance Harry. The static type system can ensure that object-oriented languages. But most languages that support any messages that Harry responds to are also understood by metaclasses impose severe restrictions on their use. Typi- any other instance of Eagle. cally, a metaclass is allowed to have only a single instance However, even in a language where classes can have static and all metaclasses are required to share a common super- methods, the desired relationships cannot be expressed. For class [6]. In addition, few languages that support metaclasses example, in such a language, we can write the expression include a static type system, and none include a type system Eagle.isEndangered() provided that Eagle has the ap- with nominal subtyping (i.e., subtyping as defined in lan- propriate static method. Such a method is appropriate for guages such as the JavaTM Programming Language or C#). any class that is a species. However, if Salmon is another To elucidate the structure of metaclasses and their rela- class in our system, our type system provides us no way of tionship with static types, we present a core calculus for a requiring that it also have an isEndangered method. This nominally typed object-oriented language with metaclasses is because we cannot classify both Salmon and Eagle, when and prove type soundness over this core.
    [Show full text]
  • Protocols What Are Protocols?
    Protocols What are Protocols? • A protocol is a set of possibly interacting functions. • Example: (defgeneric read-bytes (stream n)) (defgeneric read-byte (stream)) Possible Interactions • (defgeneric read-bytes (stream n)) (defgeneric read-byte (stream)) • Option 1: (defmethod read-bytes (stream n) (let ((array (make-array n))) (loop for i below n do (setf (aref array i) (read-byte stream))) array)) Possible Interactions • (defgeneric read-bytes (stream n)) (defgeneric read-byte (stream)) • Option 2: (defmethod read-byte (stream) (let ((array (read-bytes 1))) (aref array 0))) Possible Interactions • (defgeneric read-bytes (stream n)) (defgeneric read-byte (stream)) • Option 3: No interactions. (The two generic functions are independent.) • Why does it matter? You have to know what you can override and what effects overriding has. Protocols in CLOS • CLOS defines some protocols for its operators. make-instance • (defmethod make-instance (class &rest initargs) ... (let ((instance (apply #’allocate-instance class initargs))) (apply #’initialize-instance instance initargs) instance)) initialize-instance • (defmethod initialize-instance ((instance standard-object) &rest initargs) (apply #’shared-initialize instance t initargs)) Initialization Protocol • make-instance calls allocate-instance and then initialize-instance. • allocate-instance allocates storage. • initialize-instance calls shared-initialize. • shared-initialize assigns the slots. change-class • change-class modifies the object to be an instance of a different class and then calls update-instance-for-different-class. • update-instance-for-different-class calls shared-initialize. reinitialize-instance • reinitialize-instance calls shared-initialize. Class Redefinition • When a class is redefined, make-instances-obsolete may be called. • make-instances-obsolete ensures that update-instance-for-redefined-class is called for each instance.
    [Show full text]
  • Using a Loadtime Metaobject Protocol to Enforce Access Control Policies Upon User-Level Compiled Code
    USING A LOADTIME METAOBJECT PROTOCOL TO ENFORCE ACCESS CONTROL POLICIES UPON USER-LEVEL COMPILED CODE ,\ DISSERTAIION SUBMITTED TO THE SCHOOL OF C();-"ll'lTI~G OF THE UNIVERSITY OF NEWCASTLE-UPON-TYNE IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Ian S. Welch September 2004 NEWC~STL[ UNIVCRSITY LICRARY 204 OGJ32 0 © Copyright by Ian S. Welch 200-+ All Rights Reserved 11 Dedication To my partner Jim and, my family especially my parents Stan and Claire. III Acknowledgements I would like to express my sincere gratitude to "everal people \\ho ha\e contributed in various ways to the completion of this thesis. The advice and patience of my supervisor, Dr. Robert Stroud, \\ <1" crucial in the comple­ tion of this work. Also, many thank.., to the Defence and Research Agency and particularly Dr. Peter Y. Ryan for providing the financial support, advice and encouragement needed to fini..,h my work. While at Newcastle, the advice and help given to me by a large number of people, in particular Dr. G. Morgan, Mr J. Warne, Dr. A.S. McGough, Dr. B. ArieL Dr. A. Ro­ manovsky, and Dr. C. Gaciek kept me going. Since leaving Newca..,tle and coming to \\ork at Victoria University, I have been greatly helped by the contributions of my colleagues. Participation in the Circle of Guilt has been a great help in completing but abo staying sane. Special thanks also to Margi Key" for helping proofread the final thesi" and keeping me on the straight and narrow with the use of my hyphens! Finally, I would not have started or completed this thesis if it hadn't been for the en­ couragement and support of my partner, Jim Whitman.
    [Show full text]