Subject: PEM Talks Frank Tip, Friday 12 June 2009
From: "H.J.S. Basten" 
To: pem-list, sen-list
Date: Mon, 08 Jun 2009 16:03:22 +0200

Dear all,

You are hereby cordially invited for our next PEM talks on Friday 12
June 2009. We are very pleased to introduce Frank Tip, who is visiting
us from IBM Research. He will give the following two talks:


1. Refactoring using Type Constraints

(joint work with Robert Fuhrer, Adam Kiezun, Michael Ernst, Ittai
Balaban, and Bjorn De Sutter)

Type constraints express subtype-relationships between the types of
program expressions that are required for type-correctness, and were
originally proposed as a convenient framework for solving type checking
and type inference problems. In this paper, we show how type constraints
can be used as the basis for practical refactoring tools. In our
approach, a set of type constraints is derived from a type-correct
program P. The main insight behind our work is the fact that P
constitutes just one solution to this constraint system, and that
alternative solutions may exist that correspond to refactored versions
of P. We show how a number of refactorings for manipulating types and
class hierarchies can be expressed naturally using type constraints.
Several refactorings in the standard distribution of Eclipse are based
on our results.

[skip]


Date: Friday 12 June 2009
Time: 15:30 - 17:00
Room: M367, CWI

Afterwards we'll visit the nearby cafe-restaurant Polder for some
drinks. We're looking forward to your attendence.

Best regards,
Bas Basten

Subject: PEM Talks by Frank Tip, Friday 12 June 2009, *subject changed*
From: "H.J.S. Basten" 
To: pem-list, sen-list
Date: Wed, 10 Jun 2009 16:37:14 +0200

Dear all,

The subject of the second talk by Frank Tip is changed into "Declarative
Object Identity using Relation Types". See the updated invitation below:


Dear all,

You are hereby cordially invited for our next PEM talks on Friday 12
June 2009. We are very pleased to introduce Frank Tip, who is visiting
us from IBM Research. He will give the following two talks:


1. Refactoring using Type Constraints

(joint work with Robert Fuhrer, Adam Kiezun, Michael Ernst, Ittai
Balaban, and Bjorn De Sutter)

Type constraints express subtype-relationships between the types of
program expressions that are required for type-correctness, and were
originally proposed as a convenient framework for solving type checking
and type inference problems. In this paper, we show how type constraints
can be used as the basis for practical refactoring tools. In our
approach, a set of type constraints is derived from a type-correct
program P. The main insight behind our work is the fact that P
constitutes just one solution to this constraint system, and that
alternative solutions may exist that correspond to refactored versions
of P. We show how a number of refactorings for manipulating types and
class hierarchies can be expressed naturally using type constraints.
Several refactorings in the standard distribution of Eclipse are based
on our results.


2. Declarative Object Identity using Relation Types

(joint work with Mandana Vaziri, Julian Dolby, and Stephen Fink)

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, and its implementation requires tedious and error-prone
boilerplate code. Relation types are a programming model in which object
identity is defined declaratively, obviating the need for equals() and
hashCode() methods.  This entails a stricter contract: identity never
changes during an execution.  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.

Date: Friday 12 June 2009
Time: 15:30 - 17:00
Room: M367, CWI

Afterwards we'll visit the nearby cafe-restaurant Polder for some
drinks. We're looking forward to your attendence.

Best regards,
Bas Basten