From: Paul Klint
To:
Date: Wed, 14 Mar 2007 07:42:25 +0100
Subject: Two lectures by IBM researchers

You are cordially inviated for the following two lectures:

Frank Tip: 
   Declarative Object Identity using Relation Types

Robert Fuhrer:
   SAFARI: A Meta-Tooling Platform for Creating Language-Specific IDE's

Date: Monday March 19, 2007

Time: 14:00-16:00

Venue: Centrum for Wiskunde en Informatica (CWI), Kruislaan 413, Amsterdam

Room: Z009

Details can be found below.

Regards,

-- Paul Klint

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Declarative Object Identity using Relation Types

Frank Tip, IBM T.J. Watson Research Center
(joint work with Mandana Vaziri, Stephen Fink, and Julian Dolby)

Object-oriented languages define the identity of an object to be an 
address-based object identifier. The programmer may customize the notion of 
object identity by overriding the equals() and hashCode() methods following a
specified contract. This customization often introduces latent errors, since 
the contract is unenforced, and at times impossible to satisfy. Notably, equals() 
may refer to mutable state, which allows object identity to change during
execution, breaking standard library invariants.

We propose a programming model based on a relational view of the heap which
defines identity declaratively, obviating the need for equals() and hashCode() 
methods.  Each element in the heap (called a tuple) belongs to a relation type
and relates an immutable identity to mutable state. The model entails a stricter 
contract: identity never changes during an execution.  Objects, values, and 
singletons arise as special casesof tuples. 

We formalize the model as an adaptation of Featherweight Java, and implement
it by extending Java with relation types.  Experiments on a set of Java programs 
show that the majority of classes that override equals() can be refactored into 
relation types, and that most of the remainder are buggy or fragile.

This work will be presented at ECOOP'07.

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