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@inproceedings{AnconaCorradi14,
booktitle = {{ECOOP 2014 - Object-Oriented Programming}},
keywords = {{objects,types,coinduction}},
note = {{To appear}},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/CompleteCoinductiveSubtyping.pdf},
author = {Ancona, D. and Corradi, A.},
title = {{Sound and complete subtyping between coinductive types for object-oriented languages}},
year = {2014},
abstract = {Structural subtyping is an important notion for effective static type analysis;
it can be defined either axiomatically by a collection of subtyping rules, or by means of set inclusion between type interpretations, following
the semantic subtyping approach, which is more intuitive, and allows simpler proofs of the expected properties of the subtyping relation.
In object-oriented programming, recursive types typically correspond to inductively defined data structures, and subtyping is defined axiomatically;
however, in object-oriented languages objects can also be cyclic, but inductive types
cannot represent them as precisely as happens for coinductive types.
We study semantic subtyping between coinductive types with records and unions, which are particularly interesting for object-oriented programming,
show cases where it allows more precise type analysis, and develop a sound and complete effective algorithm for deciding it.
To our knowledge, this is the first proposal for a sound and complete algorithm for semantic subtyping between coinductive types.
}
}
@inproceedings{AZ_FTfJP13,
booktitle = {{Formal techniques for Java-like programs (FTfJP13)}},
keywords = {{objects, coinduction, corecursion}},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/AZ-FTfJP13.pdf},
author = {Ancona, D. and Zucca, E.},
title = {{Safe Corecursion in coFJ}},
pages = {2:1--2:7},
year = {2013},
abstract = {In previous work we have presented coFJ, an extension
to Featherweight Java that promotes coinductive
programming, a sub-paradigm expressly devised to ease
high-level programming and reasoning with cyclic data
structures. The coFJ language supports cyclic objects
and regularly corecursive methods, that is, methods
whose invocation terminates not only when the
corresponding call trace is finite (as happens with
ordinary recursion), but also when such a trace is
infinite but cyclic, that is, can be specified by a
regular term, or, equivalently, by a finite set of
recursive syntactic equations. In coFJ it is not easy
to ensure that the invocation of a corecursive method
will return a well-defined value, since the recursive
equations corresponding to the regular trace of the
recursive calls may not admit a (unique) solution; in
such cases we say that the value returned by the method
call is undetermined. In this paper we propose two new
contributions. First, we design a simpler construct for
defining corecursive methods and, correspondingly,
provide a more intuitive operational semantics. For
this coFJ variant, we are able to define a type system
that allows the user to specify that certain
corecursive methods cannot return an undetermined
value; in this way, it is possible to prevent unsafe
use of such a value. The operational semantics and the
type system of coFJ are fully formalized, and the
soundness of the type system is proved. }
}
@inproceedings{Ancona_FTfJP14,
booktitle = {{Formal techniques for Java-like programs (FTfJP14)}},
keywords = {{semantics, types, objects, coinduction}},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/Ancona-FTfJP14.pdf},
author = {Ancona, D.},
title = {{How to Prove Type Soundness of Java-like Languages Without Forgoing Big-step Semantics}},
pages = {1:1--1:6},
year = {2014},
articleno = {1},
publisher = {ACM},
abstract = {Small-step operational semantics is the most commonly employed formalism for
proving type soundness of statically typed programming languages, because
of its ability to distinguish stuck from non-terminating computations,
as opposed to big-step operational semantics.
Despite this, big-step operational semantics is more abstract, and more
useful for specifying interpreters.
In previous work we have proposed a new proof technique to prove type soundness
of a Java-like language expressed in terms of its big-step operational semantics.
However the presented proof is rather involved, since it
requires showing that the set of proof trees defining the semantic judgment forms a complete metric space
when equipped with a specific distance function.
In this paper we propose a more direct and abstract approach that exploits a standard and general compactness property
of the metric space of values, that allows approximation of the coinductive big-step semantics in terms of the small-step one;
in this way type soundness can be proved by standard mathematical induction.
}
}
@inproceedings{AnconaECOOP12,
author = {Ancona, D.},
title = {Soundness of {O}bject-{O}riented {L}anguages with
{C}oinductive {B}ig-{S}tep {S}emantics},
booktitle = {E{COOP} 2012 - {O}bject-{O}riented {P}rogramming},
editor = {Noble, J.},
volume = {7313},
pages = {459--483},
publisher = {Springer},
abstract = {It is well known that big-step operational semantics
are not suitable for proving soundness of type systems,
because of their inability to distinguish stuck from
non-terminating computations. We show how this problem
can be solved by interpreting coinductively the rules
for the standard big-step operational semantics of a
Java-like language, thus making the claim of soundness
more intuitive: whenever a program is well-typed, its
coinductive operational semantics returns a value.
Indeed, coinduction allows non-terminating computations
to return values; this is proved by showing that the
set of proof trees defining the semantic judgment forms
a complete metric space when equipped with a proper
distance function. In this way, we are able to prove
soundness of a nominal type system w.r.t. the
coinductive semantics. Since the coinductive semantics
is sound w.r.t. the usual small-step operational
semantics, the standard claim of soundness can be
easily deduced. },
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/AnconaECOOP12.pdf},
keywords = {semantics, types, objects, coinduction},
year = 2012
}
@inproceedings{AL-TCS12,
author = {Ancona, D. and Lagorio, G.},
title = {Static single information form for abstract
compilation},
booktitle = {Theoretical {C}omputer {S}cience ({IFIP} {TCS} 2012)},
editor = {Baeten, J. C.M. and Ball, T. and de Boer, F. S.},
volume = {7604},
series = {Lecture Notes in Computer Science},
pages = {10--27},
publisher = {Springer},
abstract = {In previous work we have shown that more precise type
analysis can be achieved by exploiting union types and
static single assignment (SSA) intermediate
representation (IR) of code. In this paper we exploit
static single information (SSI), an extension of SSA
proposed in literature and adopted by some compilers,
to allow assignments of more precise types to variables
in conditional branches. In particular, SSI can be
exploited rather easily and effectively to infer more
precise types in dynamic object-oriented languages,
where explicit runtime typechecking is frequently used.
We show how the use of SSI form can be smoothly
integrated with abstract compilation, our approach to
static type analysis. In particular, we define abstract
compilation based on union and nominal types for a
simple dynamic object-oriented language in SSI form
with a runtime typechecking operator, to show how
precise type inference can be.},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/AL-TCS12.pdf},
keywords = {objects,types,coinduction},
year = 2012
}
@inproceedings{AZ-CoLP12,
author = {Ancona, D. and Zucca, E.},
title = {Translating Corecursive {F}eatherweight {J}ava in
Coinductive Logic Programming},
booktitle = {{Co-LP} 2012 - A workshop on {C}oinductive {L}ogic
{P}rogramming},
abstract = {Corecursive FeatherWeight Java (coFJ) is a recently
proposed extension of the calculus FeatherWeight Java
(FJ), supporting cyclic objects and regular recursion,
and explicitly designed to promote a novel programming
paradigm inspired by coinductive Logic Programming
(coLP), based on coinductive, rather than inductive,
interpretation of recursive function definitions. We
present a slightly modified version of coFJ where the
application of a coinductive hypothesis can trigger the
evaluation of a specific expression at declaration,
rather than at use site. Following an approach inspired
by abstract compilation, we then show how coFJ can be
directly translated into coLP, when coinductive SLD is
extended with a similar feature for explicitly solving
a goal when a coinductive hypothesis is applied. Such a
translation is quite compact and, besides showing the
direct relation between coFJ and coinductive Prolog,
provides a first prototypical but simple and effective
implementation of coFJ.},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/AZ-CoLP12.pdf},
keywords = {objects, coinduction, corecursion},
year = 2012
}
@inproceedings{AZ-FTfJP12,
author = {Ancona, D. and Zucca, E.},
title = {Corecursive {F}eatherweight {J}ava},
booktitle = {Formal techniques for {J}ava-like programs
({FT}f{JP}12)},
abstract = {Despite cyclic data structures occur often in many
application domains, object-oriented programming
languages provide poor abstraction mechanisms for
dealing with cyclic objects. Such a deficiency is
reflected also in the research on theoretical
foundation of object-oriented languages; for instance,
Featherweigh Java (FJ), which is one of the most
widespread object-oriented calculi, does not allow
creation and manipulation of cyclic objects. We propose
an extension to Featherweight Java, called coFJ, where
it is possible to define cyclic objects, \{abstractly
corresponding to regular terms\}, and where an
abstraction mechanism, called regular corecursion, is
provided for supporting implementation of coinductive
operations on cyclic objects. We formally define the
operational semantics of coFJ, and provide a handful of
examples showing the expressive power of regular
corecursion; such a mechanism promotes a novel
programming style particularly well-suited for
implementing cyclic data structures, and for supporting
coinductive reasoning. },
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/AZ-FTfJP12.pdf},
keywords = {objects, coinduction, corecursion},
year = 2012
}
@inproceedings{ACLD10-FoVeOOS10,
author = {Ancona, D. and Corradi, A. and Lagorio, G. and
Damiani, F.},
title = {Abstract compilation of object-oriented languages into
coinductive {CLP}({X}): can type inference meet
verification?},
booktitle = {Formal {V}erification of {O}bject-{O}riented
{S}oftware {I}nternational {C}onference, {F}o{V}e{OOS}
2010, {P}aris, {F}rance, {J}une 28-30, 2010,
\textbf{{R}evised {S}elected {P}apers}},
editor = {Beckert, B. and March\'e, C.},
volume = {6528},
series = {Lecture Notes in Computer Science},
publisher = {Springer Verlag},
abstract = {This paper further investigates the potential and
practical applicability of abstract compilation in two
different directions. First, we formally define an
abstract compilation scheme for precise prediction of
uncaught exceptions for a simple Java-like language;
besides the usual user declared checked exceptions, the
analysis covers the runtime ClassCastException. Second,
we present a general implementation schema for abstract
compilation based on coinductive CLP with variance
annotation of user-defined predicates, and propose an
implementation based on a Prolog prototype
meta-interpreter, parametric in the solver for the
subtyping constraints.},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/ACLD10-FoVeOOS10.pdf},
keywords = {objects,types,coinduction},
year = 2011
}
@article{AL-RAIRO11,
author = {D. Ancona and G. Lagorio},
title = {Idealized coinductive type systems for imperative
object-oriented programs},
journal = {RAIRO - Theoretical Informatics and Applications},
volume = {45},
number = {1},
pages = {3-33},
abstract = {In recent work we have proposed a novel approach to
define idealized type systems for object-oriented
languages, based on abstract compilation of programs
into Horn formulas which are interpreted w.r.t. the
coinductive (that is, the greatest) Herbrand model. In
this paper we investigate how this approach can be
applied also in the presence of imperative features.
This is made possible by con- sidering a natural
translation of Static Single Assignment intermediate
form programs into Horn formulas, where phi functions
correspond to union types.},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/RAIRO.pdf},
keywords = {objects,types,coinduction},
url = {http://www.rairo-ita.org},
year = 2011
}
@inproceedings{AnconaFTfJP11,
author = {Ancona, D.},
title = {Coinductive big-step operational semantics for type
soundness of {J}ava-like languages},
booktitle = {Formal {T}echniques for {J}ava-like {P}rograms
({FT}f{JP}11)},
pages = {5:1--5:6},
publisher = {ACM},
abstract = {We define a coinductive semantics for a simple
Java-like language by simply interpreting coinductively
the rules of a standard big-step operational semantics.
We prove that such a semantics is sound w.r.t. the
usual small-step operational semantics, and then prove
soundness of a conventional nominal type system w.r.t.
the coinductive semantics. From these two results,
soundness of the type system w.r.t. the small-step
semantics can be easily deduced. This new proposed
approach not only opens up new possibilities for
proving type soundness, but also provides useful
insights on the connection between coinductive big-step
operational semantics and type systems.},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/FTfJP11.pdf},
isbn = {978-1-4503-0893-9},
keywords = {semantics, types, objects, coinduction},
year = 2011
}
@techreport{AL-10-11,
author = {Ancona, D. and Lagorio, G.},
title = {On sound and complete axiomatization of coinductive
subtyping for object-oriented languages},
institution = {DISI},
note = {Submitted for journal publication. Extended version of
\url{http://www.disi.unige.it/person/AnconaD/papers/Conferences_abstracts.html#AL-FTfJP10}{FTfJP10}},
abstract = {Coinductive abstract compilation is a novel technique,
which has been recently introduced for defining precise
type systems for object- oriented languages. In this
approach, type inference consists in translating the
program to be analyzed into a Horn formula f, and in
resolving a certain goal w.r.t. the coinductive (that
is, the greatest) Herbrand model of f. Type systems
defined in this way are idealized, since types and,
con- sequently, goal derivations, are not finitely
representable. Hence, sound implementable
approximations have to rely on the notions of regular
types and derivations, and of subtyping and subsumption
between types and atoms, respectively. In this paper we
address the problem of defining a sound and complete
axiomatization of a subtyping relation between
coinductive object and union types, defined as set
inclusion between type interpretations. Besides being
an important theoretical result, completeness is useful
for reasoning about possible implementations of the
subtyping relation, when restricted to regular types.},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/AL10-11.pdf},
keywords = {objects,types,coinduction},
month = nov,
year = 2010
}
@techreport{ACLD10-08-ext,
author = {Ancona, D. and Corradi, A. and Lagorio, G. and
Damiani, F.},
title = {Abstract compilation of object-oriented languages into
coinductive {CLP}({X}): can type inference meet
verification? (extended version)},
institution = {DISI},
note = {Extended version of \url{http://www.disi.unige.it/person/AnconaD/papers/Conferences_abstracts.html#ACLD10-FoVeOOS10}{FoVeOOS10}},
abstract = {This paper further investigates the potential and
practical applicability of abstract compilation in two
different directions. First, we formally define an
abstract compilation scheme for precise prediction of
uncaught exceptions for a simple Java-like language;
besides the usual user declared checked exceptions, the
analysis covers the runtime ClassCastException. Second,
we present a general implementation schema for abstract
compilation based on coinductive CLP with variance
annotation of user-defined predicates, and propose an
implementation based on a Prolog prototype
meta-interpreter, parametric in the solver for the
subtyping constraints. },
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/ACLD10ext.pdf},
keywords = {objects,types,coinduction},
month = aug,
year = 2010
}
@inproceedings{AL-FTfJP10,
author = {D. Ancona and G. Lagorio},
title = {Complete coinductive subtyping for abstract
compilation of object-oriented languages},
booktitle = {F{TFJP} '10: {P}roceedings of the 12th {W}orkshop on
{F}ormal {T}echniques for {J}ava-{L}ike {P}rograms},
series = {ACM Digital Library},
pages = {1:1--1:7},
publisher = {ACM},
abstract = {Coinductive abstract compilation is a novel technique,
which has been recently introduced, for defining
precise type systems for object-oriented languages. In
this approach, type inference consists in translating
the program to be analyzed into a Horn formula f, and
in resolving a certain goal w.r.t. the coinductive
(that is, the greatest) Herbrand model of f. Type
systems defined in this way are idealized, since types
and, consequently, goal derivations, are not finitely
representable. Hence, sound implementable
approximations have to rely on the notions of regular
types and derivations, and of subtyping and subsumption
between types and atoms, respectively. In this paper we
address the problem of defining a complete subtyping
relation <= between types built on object and union
type constructors: we interpret types as sets of
values, and investigate on a definition of subtyping
such that t\_1 <= t\_2 is derivable whenever the
interpretation of t\_1 is contained in the
interpretation of t\_2. Besides being an important
theoretical result, completeness is useful for
reasoning about possible implementations of the
subtyping relation, when restricted to regular types. },
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/FTfJP10.pdf},
keywords = {objects,types,coinduction},
url = {http://portal.acm.org/citation.cfm?id=1924520},
year = 2010
}
@inproceedings{AL10-GandALF10,
author = {D. Ancona and G. Lagorio},
title = {Coinductive subtyping for abstract compilation of
object-oriented languages into {H}orn formulas},
booktitle = {Proceedings of {G}and{ALF} 2010},
editor = {{Montanari A.} and {Napoli M.} and {Parente M.}},
volume = {25},
series = {Electronic Proceedings in Theoretical Computer Science},
pages = {214--223},
abstract = {In recent work we have shown how it is possible to
define very precise type systems for object-oriented
languages by abstractly compiling a program into a Horn
formula f. Then type inference amounts to resolving a
certain goal w.r.t. the coinductive (that is, the
greatest) Herbrand model of f. Type systems defined in
this way are idealized, since in the most interesting
instantiations both the terms of the coinductive
Herbrand universe and goal derivations cannot be
finitely represented. However, sound and quite
expressive approximations can be implemented by
considering only regular terms and derivations. In
doing so, it is essential to introduce a proper
subtyping relation formalizing the notion of
approximation between types. In this paper we study a
subtyping relation on coinductive terms built on union
and object type constructors. We define an
interpretation of types as set of values induced by a
quite intuitive relation of membership of values to
types, and prove that the definition of subtyping is
sound w.r.t. subset inclusion between type
interpretations. The proof of soundness has allowed us
to simplify the notion of contractive derivation and to
discover that the previously given definition of
subtyping did not cover all possible representations of
the empty type. },
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/GandALF10.pdf},
keywords = {objects,types,coinduction},
year = 2010
}
@techreport{AnconaEtAl10,
author = {Ancona, D. and Corradi, A. and Lagorio, G. and
Damiani, F.},
title = {Abstract compilation of object-oriented languages into
coinductive {CLP}({X}): when type inference meets
verification},
institution = {Karlsruhe Institute of Technology},
note = {Formal {V}erification of {O}bject-{O}riented
{S}oftware. {P}apers presented at the {I}nternational
{C}onference, {J}une 28-30, 2010, {P}aris, {F}rance},
abstract = {We propose a novel general approach for defining
expressive type systems for object-oriented languages,
based on abstract compilation of programs into
coinductive constraint logic programs defined on a
specific constraint domain X called type domain. In
this way, type checking and type inference amount to
resolving a certain goal w.r.t. the coinductive (that
is, the greatest) Herbrand model of a logic program
(that is, a Horn formula) with constraints over a fixed
type domain X. In particular, we show an interesting
instantiation where the constraint predicates of X are
syntactic equality and subtyping over coinductive
object and union types. The corresponding type system
is so expressive to allow verification of simple
properties like data structure invariants. Finally, we
show a prototype implementation, written in Prolog, of
the inference engine for coinductive CLP(X), which is
parametric in the solver for the type domain X.},
booktitle = {Formal {V}erification of {O}bject-{O}riented
{S}oftware. {P}apers presented at the {I}nternational
{C}onference, {J}une 28-30, 2010, {P}aris, {F}rance},
editor = {Beckert, B. and March\'e, C.},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/FOVEOOS10-preproc.pdf},
keywords = {objects,types,coinduction},
publisher = {Karlsruhe},
series = {Karlsruhe Reports in Informatics (fr\"uher: Interner
Bericht. Fakult\"at f\"ur Informatik, Karlsruher
Institut f\"ur Technologie) ; 2010,13},
year = 2010
}
@inproceedings{CAR-ICOOLPS09,
author = {Cuni, A. and Ancona, D. and Rigo, A.},
title = {Faster than {C}\#: efficient implementation of dynamic
languages on {.NET}},
booktitle = {{ICOOOLPS} '09: Proceedings of the 4th workshop on the
{I}mplementation, {C}ompilation, {O}ptimization of
{O}bject-{O}riented {L}anguages and {P}rogramming
{S}ystems},
pages = {26--33},
address = {New York, NY, USA},
publisher = {ACM},
abstract = {The Common Language Infrastructure (CLI) is a virtual
machine expressly designed for implementing statically
typed languages such as C\#, therefore programs written
in dynamically typed languages are typically much
slower than C\# when executed on .NET. Recent
developments show that Just In Time (JIT) compilers can
exploit runtime type information to generate quite
efficient code. Unfortunately, writing a JIT compiler
is far from being simple. In this paper we report our
positive experience with automatic generation of JIT
compilers as supported by the PyPy infrastructure, by
focusing on JIT compilation for .NET. Following this
approach, we have in fact added a second layer of JIT
compilation, by allowing dynamic generation of more
efficient .NET bytecode, which in turn can be compiled
to machine code by the .NET JIT compiler. The main and
novel contribution of this paper is to show that this
two-layers JIT technique is effective, since programs
written in dynamic languages can run on .NET as fast as
(and in some cases even faster than) the equivalent C\#
programs. The practicality of the approach is
demonstrated by showing some promising experiments done
with benchmarks written in a simple dynamic language. },
doi = {http://doi.acm.org/10.1145/1565824.1565828},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/ICOOOLPS09.pdf},
isbn = {978-1-60558-541-3},
keywords = {objects,dynamicLang},
location = {Genova, Italy},
year = 2009
}
@inproceedings{ALZ-TYPES08,
author = {Ancona, D. and Lagorio, G. and Zucca, E.},
title = {Type inference by coinductive logic programming},
booktitle = {Post-{P}roceedings of {TYPES} 2008},
editor = {Berardi S., Damiani F., de' Liguoro U.},
volume = {5497},
series = {Lecture Notes in Computer Science},
publisher = {Springer Verlag},
abstract = {We propose a novel approach to constraint-based type
inference based on coinductive logic programming. That
is, constraint generation corresponds to translation
into a conjunction of Horn clauses P, and constraint
satisfaction is defined in terms of the maximal
coinductive Herbrand model of P. We illustrate the
approach by formally defining this translation for a
small object-oriented language similar to Featherweight
Java, where type annotations in field and method
declarations can be omitted. In this way, we obtain a
very precise type inference and provide new insights
into the challenging problem of type inference for
object-oriented programs. Since the approach is
deliberately declarative, we define in fact a formal
specification for a general class of algorithms, which
can be a useful road maps to researchers. Moreover,
despite we consider here a particular language, the
methodology could be used in general for providing
abstract specifications of type inference for different
kinds of programming languages.},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/ALZ0908.pdf},
keywords = {objects,types,coinduction},
year = 2009
}
@inproceedings{AL-ECOOP09,
author = {Ancona, D. and Lagorio, G.},
title = {Coinductive type systems for object-oriented languages},
booktitle = {ECOOP 2009 - Object-Oriented Programming},
editor = {{S. Drossopoulou}},
volume = {5653},
series = {Lecture Notes in Computer Science},
pages = {2--26},
publisher = {Springer Verlag},
note = {\textbf{Best paper prize}},
abstract = {We propose a novel approach based on coinductive logic
to specify type systems of programming languages. The
approach consists in encoding programs in Horn formulas
which are interpreted w.r.t. their coinductive Herbrand
model. We illustrate the approach by first specifying a
standard type system for a small object-oriented
language similar to Featherweight Java. Then we define
an idealized type system for a variant of the language
where type annotations can be omitted. The type system
involves infinite terms and proof trees not
representable in a finite way, thus providing a
theoretical limit to type inference of object-oriented
programs, since only sound approximations of the system
can be implemented. Approximation is naturally captured
by the notions of subtyping and subsumption; indeed,
rather than increasing the expressive power of the
system, as it usually happens, here subtyping is needed
for approximating infinite non regular types and proof
trees with regular ones. },
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/ECOOP09.pdf},
keywords = {objects,types,coinduction},
year = 2009
}
@techreport{ABCR1208,
author = {Ancona, D. and Bolz, C. and Cuni, A. and Rigo, A.},
title = {Automatic generation of {JIT} compilers for dynamic
languages in .{NET}},
institution = {Univ. of Dusseldorf and Univ. of Genova},
abstract = {Writing an optimizing static compiler for dynamic
languages is not an easy task, since quite complex
static analysis is required. On the other hand, recent
developments show that JIT compilers can exploit
runtime type information to generate quite efficient
code. Unfortunately, writing a JIT compiler is far from
being simple. In this paper we report our positive
experience with automatic generation of JIT compilers
as supported by the PyPy infrastructure, by focusing on
JIT compilation for .NET. The paper presents two main
and novel contributions: we show that partial
evaluation can be used in practice for generating a JIT
compiler, and we experiment with the potentiality
offered by the ability to add a further level of JIT
compilation on top of .NET. The practicality of the
approach is demonstrated by showing some promising
experiments done with benchmarks written in a simple
dynamic language.},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/ABCR1208.pdf},
keywords = {objects,dynamicLang},
month = dec,
year = 2008
}
@techreport{AM1208,
author = {Ancona, D. and Mascardi, V.},
title = {Ontology matching for semi-automatic and type-safe
adaptation of {J}ava programs},
institution = {DISI - Univ. of Genova},
abstract = {This paper proposes a solution to the problem of
semi-automatic porting of Java programs. In particular,
our work aims at the design of tools able to aid users
to adapt Java code in a type-safe way, when an
application has to migrate to new libraries which are
not fully compatible with the legacy ones. To achieve
this, we propose an approach based on an integration of
the two type-theoretic notions of subtyping and type
isomorphism with ontology matching. While the former
notions are needed to ensure flexible adaptation in the
presence of type-safety, the latter supports the user
to preserve the semantics of the program to be adapted.
},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/AM1208.pdf},
keywords = {objects,types,refactoring},
month = dec,
year = 2008
}
@techreport{ALZ0708,
author = {Ancona, D. and Lagorio, G. and Zucca, E.},
title = {Type inference for {J}ava-like programs by coinductive
logic programming},
institution = {DISI - Univ. of Genova},
abstract = {Although coinductive logic programming (Co-LP) has
proved to have several applications, including
verification of infinitary properties, model checking
and bisimilarity proofs, type inference via Co-LP has
not been properly investigated yet. In this paper we
show a novel approach to solve the problem of type
inference in the context of Java-like languages, that
is, object-oriented languages based on nominal
subtyping. The proposed approach follows a generic
scheme: first, the program P to be analyzed is
translated into an approximating logic program P' and a
goal G; then, the solution of the type inference
problem corresponds to find an instantiation of the
goal G which belongs to the greatest model of P', that
is, the coinductive model of P'. Operationally, this
corresponds to find a co-SLD derivation of G in P',
according to the operational semantics of Co-LP
recently defined by Simon et al. [ICLP06,ICALP07]. A
complete formalization of an instantiation of this
scheme is considered for a simple object-oriented
language and a corresponding type soundness theorem is
stated. A prototype implementation based on a
meta-interpreter of co-SLD has been implemented.
Finally, we address scalability issues of the approach,
by sketching an instantiation able to deal with a much
more expressive object-oriented language.},
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/ALZ0708.pdf},
keywords = {objects,types,coinduction},
month = jul,
year = 2008
}
@techreport{ALZ0408,
author = {Ancona, D. and Lagorio, G. and Zucca, E.},
title = {A flexible and type-safe framework of components for
{J}ava-like languages},
institution = {DISI - Univ. of Genova},
note = {Submitted for journal publication. Extended version of
\url{http://www.disi.unige.it/person/AnconaD/papers/Conferences_abstracts.html#ALZ-JMLC06}{JMLC06}},
abstract = {We define a framework of components based on Java-like
languages, where components are binary mixin modules.
Basic components can be obtained from a collection of
classes by compiling such classes in isolation; for
allowing that, requirements in the form of type
constraints are associated with each class.
Requirements are specified by the user who, however, is
assisted by the compiler that can generate missing
constraints essential to guarantee type safety. Basic
components can be composed together by using a set of
expressive typed operators; thanks to soundness
results, such a composition is always type safe. The
framework is designed as a separate layer that can be
instantiated on top of any Java-like language; to show
the effectiveness of the approach, an instantiation on
a small Java subset is provided, together with a
prototype implementation. Besides safety, the approach
achieves great flexibility in reusing components for
two reasons: (1) type constraints generated for a
single component exactly capture all possible contexts
where it can be safely used; (2) composition of
components is not limited to conventional linking, but
is achieved by means of a set of powerful operators
typical of mixin modules. },
ftp = {ftp://ftp.disi.unige.it/person/AnconaD/FTFCJL.pdf},
keywords = {objects,types,components},
month = apr,
year = 2008
}
@article{AADDGZ-TOPLAS07,
author = {D.~Ancona and C.~Anderson and F.~Damiani and
S.~Drossopoulou and P.~Giannini and E.~Zucca},
title = {A {P}rovenly {C}orrect {T}ranslation of {F}ickle into
{J}ava},
journal = {ACM Transactions on Programming Languages and Systems},
volume = {29},
number = {2},
abstract = {We present a translation from Fickle, a small
object-oriented language allowing objects to change
their class at runtime, into Java. The translation is
provenly correct in the sense that it preserves the
static and dynamic semantics. Moreover, it is
compatible with separate compilation, since the
translation of a Fickle class does not depend on the
implementation of used classes. Based on the formal
system, we have developed an implementation. The
translation turned out to be a more subtle problem than
we expected. In this article, we discuss four possible
approaches we considered for the design of the
translation and to justify our choice, we present
formally the translation and proof of preservation of
the static and dynamic semantics, and discuss the
prototype implementation. Moreover, we outline an
alternative translation based on generics that avoids
most of the casts (but not all) needed in the previous
translation. The language Fickle has undergone and is
still undergoing several phases of development. In this
article we are discussing the translation of FickleII. },
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/TOPLAS07.pdf},
keywords = {objects, types},
month = apr,
year = 2007
}
@inproceedings{ALZ-ICTCS07,
author = {D.~Ancona and G.~Lagorio and E.~Zucca},
title = {Type inference for polymorphic methods in {J}ava-like
languages},
booktitle = {Theoretical {C}omputer {S}cience: {P}roceedings of the
10th {I}talian {C}onference on {ICTCS} '07},
editor = {Italiano, G. and Moggi, E. and Laura, L.},
publisher = {World Scientific},
note = {See also the
\url{ftp://ftp.disi.unige.it/pub/person/AnconaD/TIPMJLlong.pdf}{long
version} with proofs},
abstract = {In languages like C++, Java and C#, typechecking
algorithms require methods to be annotated with their
parameter and result types, which are either fixed or
constrained by a bound. We show that, surprisingly
enough, it is possible to infer the polymorphic type of
a method where parameter and result types are left
unspecified, as happens in most functional languages.
These types intuitively capture the (less restrictive)
requirements on arguments needed to safely apply the
method. We formalize our ideas on a minimal Java
subset, for which we define a type system with
polymorphic types and prove its soundness. We then
describe an algorithm for type inference and prove its
soundness and completeness. A prototype implementing
inference of polymorphic types is available.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/ALZ-ICTCS07.pdf},
keywords = {objects, types},
year = 2007
}
@inproceedings{AACM-DLS07,
author = {Ancona, D. and Ancona, M. and Cuni, A and Matsakis, N.},
title = {R{P}ython: a {S}tep {T}owards {R}econciling
{D}ynamically and {S}tatically {T}yped {OO} {L}anguages},
booktitle = {O{OPSLA} 2007 {P}roceedings and {C}ompanion, {DLS}'07:
{P}roceedings of the 2007 {S}ymposium on {D}ynamic
{L}anguages},
pages = {53--64},
publisher = {ACM},
abstract = {Although the C-based interpreter of Python is
reasonably fast, implementations on the CLI or the JVM
platforms offers some advantages in terms of robustness
and interoperability. Unfortunately, because the CLI
and JVM are primarily designed to execute statically
typed, object-oriented languages, most dynamic language
implementations cannot use the native bytecodes for
common operations like method calls and exception
handling; as a result, they are not able to take full
advantage of the power offered by the CLI and JVM. We
describe a different approach that attempts to preserve
the flexibility of Python, while still allowing for
efficient execution. This is achieved by limiting the
use of the more dynamic features of Python to an
initial, bootstrapping phase. This phase is used to
construct a final RPython (Restricted Python) program
that is actually executed. RPython is a proper subset
of Python, is statically typed, and does not allow
dynamic modification of class or method definitions;
however, it can still take advantage of Python features
such as mixins and first-class methods and classes.
This paper presents an overview of RPython, including
its design and its translation to both CLI and JVM
bytecode. We show how the bootstrapping phase can be
used to implement advanced features, like extensible
classes and generative programming. We also discuss
what work remains before RPython is truly ready for
general use, and compare the performance of RPython
with that of other approaches.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/DLS08.pdf},
keywords = {objects,dynamicLang},
year = 2007
}
@inproceedings{ALZ-JMLC06,
author = {D.~Ancona and G.~Lagorio and E.~Zucca},
title = {Flexible Type-Safe Linking of Components for
{J}ava-like Languages},
booktitle = {Joint {M}odular {L}anguages {C}onference ({JMLC} 2006)},
volume = {4228},
series = {Lecture Notes in Computer Science},
pages = {136--154},
publisher = {Springer Verlag},
note = {See also the \url{Reports.html#FTFCJL}{extended
version}},
abstract = {We define a framework of components based on Java-like
languages, where components are binary mixin modules.
Basic components can be obtained from a collection of
classes by compiling such classes in isolation; for
allowing that, requirements in the form of type
constraints are associated with each class.
Requirements are specified by the user who, however, is
assisted by the compiler which can generate missing
constraints essential to guarantee type safety. Basic
components can be composed together by using a set of
expressive typed operators; thanks to soundness
results, such a composition is always type safe. The
framework is designed as a separate layer which can be
instantiated on top of any Java-like language; a
prototype implementation is available for a small Java
subset. Besides safety, the approach achieves great
flexibility in reusing components for two reasons: (1)
type constraints generated for a single component
exactly capture all possible contexts where it can be
safely used; (2) composition of components is not
limited to conventional linking, but is achieved by
means of a set of powerful operators typical of mixin
modules. },
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/JMLC06.pdf},
keywords = {objects, types, components},
year = 2006
}
@inproceedings{ALZ-FTfJP05,
author = {D.~Ancona and G.~Lagorio and E.~Zucca},
title = {Smart Modules for {J}ava-like Languages},
booktitle = {7th Intl. Workshop on Formal Techniques for Java-like Programs 2005},
abstract = {We present SmartJavaMod, a language of mixin modules
supporting compositional compilation, and constructed
on top of the Java language. More in detail, this means
that basic modules are collections of Java classes
which can be typechecked in isolation, inferring
constraints on missing classes and allowing safe reuse
of the module in as many contexts as possible.
Furthermore, it is possible to write structured module
expressions by means of a set of module operators, and
a type system at the module level ensures type safety,
in the sense that we can always reduce a module
expression to a well-formed collection of Java classes.
What we obtain is a module language which is extremely
flexible and allows the encoding (without any need of
enriching the core level, that is, the Java language)
of a variety of constructs supporting software reuse
and extensibility.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/SMJL.pdf},
keywords = {types, objects, components},
month = jul,
year = 2005
}
@techreport{ADDZ05,
author = {D.~Ancona and F.~Damiani and S.~Drossopoulou and
E.~Zucca},
title = {Compositional {C}ompilation for {J}ava-like
{L}anguages through {P}olymorphic {B}ytecode},
institution = {Dipartimento di Informatica e Scienze dell'Informazione, Universit\`a di Genova},
abstract = {We define compositional compilation as the ability to
typecheck source code fragments in isolation, generate
corresponding binaries, and link together fragments
whose mutual assumptions are satisfied, without
reinspecting the code. Even though compositional
compilation is a highly desirable feature, in Java-like
languages it can hardly be achieved. This is due to the
fact that the bytecode generated for a fragment (say, a
class) is not uniquely determined by its source code,
but also depends on the compilation context. We propose
a way to obtain compositional compilation for Java, by
introducing a polymorphic form of bytecode containing
type variables (ranging over class names) and equipped
with a set of constraints involving type variables.
Thus, polymorphic bytecode provides a representation
for all the (standard) bytecode that can be obtained by
replacing type variables with classes satisfying the
associated constraints. We illustrate our proposal by
developing a typing and a linking algorithm. The typing
algorithm compiles a class in isolation generating the
corresponding polymorphic bytecode fragment and
constraints on the classes it depends on. The linking
algorithm takes a collection of polymorphic bytecode
fragments, checks their mutual consistency, and
possibly simplifies and specializes them. In
particular, linking a self-contained collection of
fragments either fails, or produces standard bytecode
(the same as what would have been produced by standard
compilation of all fragments).},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/PBCCJL.pdf},
keywords = {types, objects},
month = jan,
year = 2005
}
@inproceedings{ADDZ-POPL05,
author = {D.~Ancona and F.~Damiani and S.~Drossopoulou and
E.~Zucca},
title = {Polymorphic Bytecode: Compositional Compilation for
{J}ava-like Languages},
booktitle = {P{OPL} 2005 - {T}he 32nd {ACM} {SIGPLAN}-{SIGACT}
{S}ymposium on {P}rinciples of {P}rogramming
{L}anguages},
pages = {26--37},
publisher = {ACM Press},
abstract = {We define compositional compilation as the ability to
typecheck source code fragments in isolation, generate
corresponding binaries, and link together fragments
whose mutual assumptions are satisfied, without
reinspecting the code. Even though compositional
compilation is a highly desirable feature, in Java-like
languages it can hardly be achieved. This is due to the
fact that the bytecode generated for a fragment (say, a
class) is not uniquely determined by its source code,
but also depends on the compilation context. We propose
a way to obtain compositional compilation for Java, by
introducing a polymorphic form of bytecode containing
type variables (ranging over class names) and equipped
with a set of constraints involving type variables.
Thus, polymorphic bytecode provides a representation
for all the (standard) bytecode that can be obtained by
replacing type variables with classes satisfying the
associated constraints. We illustrate our proposal by
developing a typing and a linking algorithm. The typing
algorithm compiles a class in isolation generating the
corresponding polymorphic bytecode fragment and
constraints on the classes it depends on. The linking
algorithm takes a collection of polymorphic bytecode
fragments, checks their mutual consistency, and
possibly simplifies and specializes them. In
particular, linking a self-contained collection of
fragments either fails, or produces standard bytecode
(the same as what would have been produced by standard
compilation of all fragments).},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/POPL05.pdf},
keywords = {types, objects},
year = 2005
}
@article{AL-JOT04,
author = {D.~Ancona and G.~Lagorio},
title = {{S}tronger {T}ypings for {S}marter {R}ecompilation of
{J}ava-like {L}anguages},
journal = {Journal of Object Technology. Special issue. Workshop
on Formal Techniques for Java-like Programs (FTfJP)
ECOOP 2003},
volume = 3,
number = 6,
pages = {5-25},
abstract = {We define an algorithm for smarter recompilation of a
small but significant Java-like language; such an
algorithm is inspired by a type system previously
defined by Ancona and Zucca. In comparison with all
previous type systems for Java-like languages, this
system enjoys the principal typings property, and is
based on the two novel notions of local type assumption
and entailment of type environments. The former allows
the user to specify minimal requirements on the source
fragments which need to be compiled in isolation,
whereas the latter syntactically captures the concept
of stronger type assumption. One of the most important
practical advantages of this system is a better support
for selective recompilation; indeed, it is possible to
define an algorithm directly driven by the typing rules
which is able to avoid the unnecessary recompilation
steps which are usually performed by the Java
compilers. The algorithm is smarter in the sense that
it never forces useless recompilations, that is,
recompilations which would generate the same binary
fragment obtained from the previous compilation of the
same source fragment. Finally, we show that the
algorithm can actually speed up the overall
recompilation process, since checking for recompilation
is always strictly less expensive than recompiling the
same fragment.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/FTfJP03.ps.gz},
http = {http://www.disi.unige.it/person/AnconaD/Software/FJsc/},
keywords = {objects, types},
month = jun,
url = {http://www.jot.fm/issues/issue_2004_06/},
year = 2004
}
@inproceedings{AZ-POPL04,
author = {D.~Ancona and E.~Zucca},
title = {Principal Typings for {J}ava-like languages},
booktitle = {P{OPL} 2004 - {T}he 31st {ACM} {SIGPLAN}-{SIGACT}
{S}ymposium on {P}rinciples of {P}rogramming
{L}anguages},
pages = {306--317},
publisher = {ACM Press},
abstract = {The contribution of the paper is twofold. First, we
provide a general notion of type system supporting
separate compilation and inter-checking, and a formal
definition of soundess and completeness of
inter-checking w.r.t. global compilation. These
properties are important in practice since they allow
selective recompilation. In particular, we show that
they are guaranteed when the type system has principal
typings and provides sound and complete entailment
relation between type environments and types. The
second contribution is more specific, and is an
instantiation of the notion of type system previously
defined for Featherweight Java [IgarashiEtAl99] with
method overloading and field hiding. The aim is to show
that it is possible to define type systems for
Java-like languages, which, differently from those used
by standard compilers, have principal typings, hence
can be used as a basis for selective recompilation.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/POPL04.ps.gz},
keywords = {types, objects},
year = 2004
}
@article{ALZ-TOPLAS03,
author = {D.~Ancona and G.~Lagorio and E.~Zucca},
title = {{Jam}--designing a {Java} extension with mixins},
journal = {ACM Transactions on Programming Languages and Systems},
volume = {25},
number = {5},
pages = {641-712},
abstract = {In this paper we present Jam, an extension of the Java
language supporting mixins, that is, parametric heir
classes. A mixin declaration in Jam is similar to a
Java heir class declaration, except that it does not
extend a fixed parent class, but simply specifies the
set of fields and methods a generic parent should
provide. In this way, the same mixin can be
instantiated on many parent classes, producing
different heirs, thus avoiding code duplication and
largely improving modularity and reuse. Moreover, as
happens for classes and interfaces, mixin names are
reference types, and all the classes obtained by
instantiating the same mixin are considered subtypes of
the corresponding type, hence can be handled in a
uniform way through the common interface. This
possibility allows a programming style where different
ingredients are ``mixed'' together in defining a class;
this paradigm is somewhat similar to that based on
multiple inheritance, but avoids its complication. The
language has been designed with the main objective in
mind to obtain, rather than a new theoretical language,
a working and smooth extension of Java. That means, on
the design side, that we have faced the challenging
problem of integrating the Java overall principles and
complex type system with this new notion; on the
implementation side, that we have developed a Jam to
Java translator which makes Jam sources executable on
every Java Virtual Machine.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/TOPLAS03.ps.gz},
keywords = {objects, types},
month = sep,
url = {http://www.disi.unige.it/person/LagorioG/jam/},
year = 2003
}
@inproceedings{AL-FTfJP03,
author = {D.~Ancona and G.~Lagorio},
title = {Stronger Typings for Separate Compilation of
{J}ava-like Languages ({E}xtended {A}bstract)},
booktitle = {5th Intl. Workshop on Formal Techniques for Java Programs 2003},
abstract = {We define and implement a formal system supporting
separate compilation for a small but significant
Java-like language. This system is proved to be
stronger than the standard compilation of both Java and
C\#, in the sense that it better supports software
reuse by avoiding unnecessary recompilation steps after
code modification which are usually performed by using
the standard compilers. This is achieved by introducing
the notion of local type assumption allowing the user
to specify weaker requirements on the source fragments
which need to be compiled in isolation. Another
important property satisfied by our system is
compositionality, which corresponds to the intuition
that if a set of fragments can be separately compiled
and such fragments are compatible, then it is possible
to compile all the fragments together as a unique
program and obtain the same result.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/FTfJP03.ps.gz},
http = {http://www.disi.unige.it/person/AnconaD/Software/FJsc/},
keywords = {objects, types},
url = {http://www.cs.ru.nl/ftfjp/2003.html},
year = 2003
}
@techreport{ALZ0802,
author = {D.~Ancona and G.~Lagorio and E.~Zucca},
title = {Simplifying Types for a Calculus of {J}ava Exceptions},
institution = {Dipartimento di Informatica e Scienze dell'Informazione, Universit\`a di Genova},
note = {Submitted for journal publication},
abstract = {In this paper we present a simple calculus (called
CJE) in order to fully investigate the exception
mechanism of Java (in particular its interaction with
inheritance). We first define a type system for the
calculus, called FULL, directly driven by the Java
Language Specification and prove its soundness; then,
we show that this type system uses redundant types and
we formally capture this fact by defining equivalence
relations on types and by proving that the static
semantics of CJE programs is preserved under these
equivalences; furthermore, for each type we show that
there exists the smallest equivalent type. Finally, we
propose a simplification of the Java specification
concerning throws clause which minimally affects the
expressive power of the language.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/SimplExc.ps.gz},
keywords = {objects, types},
month = aug,
year = 2002
}
@inproceedings{ALZ-PPDP02,
author = {D. Ancona and G. Lagorio and E. Zucca},
title = {True Separate Compilation of {J}ava Classes},
booktitle = {A{CM} {SIGPLAN} {C}onference on {P}rinciples and
{P}ractice of {D}eclarative {P}rogramming ({PPDP}'02)},
pages = {189--200},
publisher = {ACM Press},
abstract = {We define a type system modeling true separate
compilation for a small but significant Java subset, in
the sense that a single class declaration can be
intra-checked (following the Cardelli's terminology)
and compiled providing a minimal set of type
requirements on missing classes. These requirements are
specified by a local type environment associated with
each single class, while in the existing formal
definitions of the Java type system classes are typed
in a global type environment containing all the type
information on a closed program. We also provide formal
rules for static inter-checking and relate our approach
with compilation of closed programs, by proving that we
get the same results. },
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/TrueSepCompLong.ps.gz},
keywords = {objects, types},
year = 2002
}
@inproceedings{ALZ-ECOOP02,
author = {D. Ancona and G. Lagorio and E. Zucca},
title = {A Formal Framework for {J}ava Separate Compilation},
booktitle = {E{COOP} 2002 - {O}bject-{O}riented {P}rogramming},
editor = {B. Magnusson},
volume = {2374},
series = {Lecture Notes in Computer Science},
pages = {609--635},
publisher = {Springer Verlag},
abstract = {We define a formal notion, called compilation schema,
allowing to specify different possibilities for
performing the overall process of Java compilation,
which includes type-checking of source fragments with
generation of corresponding binary code, type-checking
of binary fragments, extraction of type information
from fragments and definition of dependencies among
them. We consider three compilation schemata of
interest for Java, that is, minimal, SDK and safe,
which correspond to a minimal set of checks, the checks
performed by the SDK implementation, and all the checks
needed to prevent run-time linkage errors,
respectively. In order to demonstrate our approach, we
define a kernel model for Java separate compilation and
execution, consisting in a small Java subset, and a
simple corresponding binary language for which we
provide an operational semantics including run-time
verification. We define a safe compilation schema for
this language and formally prove type safety.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/ECOOP02.ps.gz},
keywords = {objects, types},
year = 2002
}
@article{AADDGZ-ENTCS02,
author = {D. Ancona and C. Anderson and F. Damiani and S.
Drossopoulou and P. Giannini and E. Zucca},
title = {A Type Preserving Translation of {F}ickle into {J}ava},
journal = {Electronic Notes in Theoretical Computer Science.
TOSCA 2001, Theory of Concurrency, Higher Order
Languages and Types},
volume = 62,
pages = {69--82},
abstract = {We present a translation from Fickle (a Java-like
language allowing objects that can change their class
at run-time) into plain Java. The translation, which
maps any Fickle class into a Java class, is driven by
an invariant that relates the Fickle object to its Java
counterpart. The translation, which is proven to
preserve both the static and the dynamic semantics of
the language, is an enhanced version of a previous
proposal by the same authors. },
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/ENTCS02.ps.gz},
keywords = {objects, types},
url = {http://www.sciencedirect.com/science?_ob=IssueURL&_tockey=%23TOC%2313109%232002%23999379999%23587065%23FLP%23&_auth=y&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=cf23278e62b455a161e5c672fa4bda20},
year = 2002
}
@inproceedings{AZ-ECOOP01,
author = {D. Ancona and E. Zucca},
title = {True Modules for {J}ava-like Languages},
booktitle = {E{COOP} 2001 - {O}bject-{O}riented {P}rogramming},
editor = {J.L. Knudsen},
volume = {2072},
series = {Lecture Notes in Computer Science},
pages = {354--380},
publisher = {Springer Verlag},
abstract = {We present JavaMod, a true module system constructed
on top of a Java-like language. More in detail, this
means that basic modules are collections of Java
classes and specify in their interface the imported and
exported classes with their types; furthermore, it is
possible to write structured module expressions by
means of a set of module operators and a type system at
the module level ensures type safety. In designing such
a type system, one has to face non trivial problems,
notably the fact that a module M which extends an
imported class C can be correctly combined only with
modules exporting a class C which, besides providing
the expected services, causes no interferences with its
subclasses defined in M. What we obtain is a module
language which is extremely flexible and allows to
express (without any need of enriching the syntax of
the core level, that is, the Java language), for
instance, generic types as in Pizza and GJ, mixin
classes (that is, subclasses parametric in the direct
superclass) and mutually recursive class definitions
split in independent modules. },
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/ECOOP01.ps.gz},
keywords = {objects, types, components},
year = 2001
}
@inproceedings{ALZ-FTfJP01,
author = {D.~Ancona and G.~Lagorio and E.~Zucca},
title = {Java separate type checking is not safe},
booktitle = {3rd Intl. Workshop on Formal Techniques for Java Programs 2001},
abstract = {Java supports separate type-checking in the sense that
compilation can be invoked on a single source fragment,
and this may enforce type-checking of other either
source or binary fragments existing in the environment.
However, the Java specification does not define precise
rules on how this process should be performed,
therefore the outcome of compilation may strongly
depend on the particular compiler implementation.
Furthermore, rules adopted by standard Java compilers,
as SDK and Jikes, can produce binary fragments whose
execution throws linking related errors. We introduce a
simple framework which allows to formally express the
process of separate compilation and the related formal
notion of type safety. Moreover, we define, for a small
subset of Java, a type system for separate compilation
which we conjecture to be safe.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/ECOOPWS01.ps.gz},
keywords = {objects, types},
url = {http://www.informatik.fernuni-hagen.de/pi5/tagungen/ecopp_2001/workshop_papers.htm},
year = 2001
}
@inproceedings{AADDGZ-ICTCS01,
author = {D. Ancona and C. Anderson and F. Damiani and S.
Drossopoulou and P. Giannini and E. Zucca},
title = {An Effective Translation of {F}ickle into {J}ava},
booktitle = {I{CTCS} 2001 - {T}heoretical {C}omputer {S}cience},
editor = {Restivo, A. and Ronchi Della Rocca, S. and Roversi, L.},
volume = {2202},
series = {Lecture Notes in Computer Science},
pages = {215-234},
publisher = {Springer Verlag},
abstract = {We present a translation from Fickle (a Java-like
language allowing dynamic object re-classification,
that is, objects that can change their class at
run-time) into plain Java. The translation is proved to
preserve static and dynamic semantics; moreover, it is
shown to be effective, in the sense that the
translation of a Fickle class does not depend on the
implementation of used classes, hence can be done in a
separate way, that is, without having their sources,
exactly as it happens for Java compilation. The aim is
to demonstrate that an extension of Java supporting
dynamic object re-classification could be fully
compatible with the existing Java environment. },
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/ICTCS01.ps.gz},
keywords = {objects, types},
year = 2001
}
@inproceedings{ALZ-OOPSLA01,
author = {D.~Ancona and G.~Lagorio and E.~Zucca},
title = {A Core Calculus for {J}ava Exceptions},
booktitle = {A{CM} {C}onference on {O}bject-{O}riented
{P}rogramming, {S}ystems, {L}anguages, and
{A}pplications ({OOPSLA} 2001)},
series = {SIGPLAN Notices},
publisher = {ACM Press},
abstract = {In this paper we present a simple calculus (called
CJE) in order to fully investigate the exception
mechanism of Java, and in particular its interaction
with inheritance, which turns out to be non trivial.
Moreover, we show that the type system for the calculus
directly driven by the Java Language Specification
(called FULL) uses too many types, in the sense that
there are different types which provide exactly the
same information. Hence, we obtain from FULL a
simplified type system called MIN where equivalent
types have been identified. We show that this is useful
both for type-checking optimization and for clarifying
the static semantics of the language. The two type
systems are proved to satisfy the subject reduction
property.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/OOPSLA01.ps.gz},
keywords = {types, objects},
year = 2001
}
@inproceedings{ADZ-FOOL01,
author = {D.~Ancona and E.~Zucca and S.~Drossopoulou},
title = {Overloading and Inheritance},
booktitle = {The {E}ighth {I}nternational {W}orkshop on
{F}oundations of {O}bject-{O}riented {L}anguages
({FOOL}8)},
abstract = {Overloading allows several function definitions for
the same name, distinguished primarily through
different argument types; it is typically resolved at
compile-time. Inheritance allows subclasses to define
more special versions of the same function; it is
typically resolved at run-time. Modern object-oriented
languages incorporate both features, usually in a
type-safe manner. However, the combination of these
features sometimes turns out to have surprising, and
even counterintuitive, effects. We discuss why we
consider these effects inappropriate, and suggest
alternatives. We explore the design space by isolating
the main issues involved and analyzing their interplay
and suggest a formal framework describing static
overloading resolution and dynamic function selection,
abstracting from other language features. We believe
that our framework clarifies the thought process going
on at language design level. We introduce a notion of
soundness and completeness of an overloading resolution
policy w.r.t. the underlying dynamic semantics, and a
way of comparing the flexibility of different
resolution policies. We apply these concepts to some
non-trivial issues raised in concrete languages. We
also argue that the semantics of overloading and
inheritance is ``clean'' only if it can be understood
through a copy semantics, whereby programs are
transformed to equivalent programs without subclasses,
and the effect of inheritance is obtained through
copying. },
ftp = {http://www.cis.upenn.edu/~bcpierce/FOOL//FOOL8/Ancona.ps.gz},
keywords = {objects, types},
year = 2001
}
@inproceedings{ALZ-ECOOP00,
author = {D.~Ancona and G.~Lagorio and E.~Zucca},
title = {{J}am: A Smooth Extension of {J}ava with Mixins},
booktitle = {E{COOP} 2000 - {O}bject-{O}riented {P}rogramming},
editor = {E. Bertino},
volume = {1850},
series = {Lecture Notes in Computer Science},
pages = {154--178},
publisher = {Springer Verlag},
abstract = {In this paper we present Jam, an extension of the Java
language supporting mixins, also called parametric heir
classes. A mixin declaration in Jam is similar to a
Java heir class declaration, apart that mixins do not
extend a fixed parent class, but simply specify the set
of fields and methods a generic parent should provide.
In this way, the same mixin can be instantiated on many
parent classes, producing different heir classes, thus
avoiding code duplication and largely improving
modularity and reuse. Moreover, as happens for classes
and interfaces, mixin names are reference types, and
all the classes obtained instantiating the same mixin
are considered subtypes of the corresponding type,
hence can be handled in a uniform way through the
common interface. This possibility allows a programming
style where different ingredients are "mixed" together
in defining a class; this paradigm is partly similar to
that based on multiple inheritance, but avoids its
complication. The language has been designed with the
main objective in mind to obtain, rather than a new
theoretical language, a working and smooth extension of
Java. That means, on the design side, that we have
faced the challenging problem of integrating the Java
overall principles and complex type system with this
new notion; on the implementation side, that we have
developed a Jam to Java translator which makes Jam
sources executable on every Java Virtual Machine. },
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/ECOOP00.ps.gz},
keywords = {objects, types},
url = {http://www.disi.unige.it/person/LagorioG/jam/},
year = 2000
}
@inproceedings{ALZ-FTfJP00,
author = {D.~Ancona and G.~Lagorio and E.~Zucca},
title = {A Core Calculus for {J}ava Exceptions ({E}xtended
{A}bstract)},
booktitle = {2nd Intl. Workshop on Formal Techniques for Java Programs 2000},
abstract = {In this paper we present a simple calculus (called
CJE) corresponding to a small functional fragment of
Java supporting exceptions. We provide a reduction
semantics for the calculus together with two equivalent
type systems; the former corresponds to the standard
specication and its formalization, whereas the latter
can be considered an optimization of the former where
only the minimal type information about
classes/interfaces and methods are collected in order
to type-check a program. The two type systems are
proved to be equivalent and a subject reduction theorem
is given.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/FTfJP00a.pdf},
keywords = {objects, types},
url = {http://www.informatik.fernuni-hagen.de/pi5/tagungen/ecoop_2000/workshop_papers.htm},
year = 2000
}
@inproceedings{AZD-FTfJP00,
author = {D.~Ancona and E.~Zucca and S.~Drossopoulou},
title = {Overloading and Inheritance in {J}ava ({E}xtended
{A}bstract)},
booktitle = {2nd Intl. Workshop on Formal Techniques for Java Programs 2000},
abstract = {The combination of overloading and inheritance in Java
introduces questions about function selection, and
makes some function calls ambiguous. We believe that
the approach taken by Java designers is
counterintuitive. We explore an alternative, and argue
that it is more intuitive and agrees with the Java
rules for the cases where Java considers the function
calls unambiguous, but gives meaning to more calls than
Java does.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/FTfJP00b.pdf},
keywords = {objects, types},
url = {http://www.informatik.fernuni-hagen.de/pi5/tagungen/ecoop_2000/workshop_papers.htm},
year = 2000
}
@inproceedings{ACZ-WADT00,
author = {D. Ancona and M. Cerioli and E. Zucca},
title = {Extending {C}asl with Late Binding},
booktitle = {W{ADT}'99 - 14th {W}orkshop on {A}lgebraic
{D}evelopment {T}echniques - {S}elected {P}apers},
editor = {Bert, D. and Choppy, C.},
volume = {1827},
series = {Lecture Notes in Computer Science},
pages = {53--72},
publisher = {Springer Verlag},
abstract = {We define an extension of CASL, the standard language
for algebraic specification, with a late binding
mechanism. More precisely, we introduce a special kind
of functions called methods, for which, differently to
what happens for usual functions, overloading
resolution is delayed at evaluation time and not
required to be conservative. The extension consists, at
the semantic level, in the definition of an institution
LB supporting late binding which is defined on top of
the standard subsorted institution of CASL and, at the
linguistic level, in the enrichment of the CASL
language with appropriate constructs for dealing with
methods.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/DISI-TR-99-14.ps.gz},
keywords = {semantics, objects},
year = 2000
}
@inproceedings{ACZ-FASE99,
author = {D. Ancona and M. Cerioli and E. Zucca},
title = {A formal framework with late binding},
booktitle = {F{ASE}'99 - {F}undamental {A}pproaches to {S}oftware
{E}ngineering},
editor = {Finance, J.-P.},
volume = {1577},
series = {Lecture Notes in Computer Science},
pages = {30--44},
publisher = {Springer Verlag},
abstract = {We define a specification formalism (formally, an
institution) which provides a notion of dynamic type
(the type which is associated to a term by a particular
evaluation) and late binding (the fact that the
function version to be invoked in a function
application depends on the dynamic type of one or more
arguments). Hence, it constitutes a natural formal
framework for modeling object-oriented and other
dynamically-typed languages and a basis for adding to
them a specification level. In this respect, the main
novelty is the capability of writing axioms related to
a given type which are not required to hold for
subtypes, hence can be ``overridden'' in further
refinements, thus lifting at the specification level
the possibility of reusing code which is offered by the
object-oriented approach. },
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/FASE99.ps.gz},
keywords = {semantics, objects},
year = 1999
}
@phdthesis{Anc98,
author = {D.~Ancona},
title = {Modular Formal Frameworks for Module Systems},
school = {Dipartimento di Informatica, Universit\`a di Pisa},
abstract = {In this thesis we present two formal frameworks for
modeling modular languages. Following a modular
approach, we separate the module and the core level of
a modular language. On the linguistic side, this
corresponds to define a kernel module language
parametric in the underlying core language. On the
semantic side, this corresponds to build a model part
(in the sense of institutions), on top of a standard
module framework. The standard module framework is a
model part, too, satisfying some additional properties
and intended as the formal counterpart of the core
language. The first formal framework we propose deals
with the notion of state, an essential component of
modules in imperative languages. The second one is
concerned with a notion of module, called mixin, which
includes those of generic module and abstract class. In
both cases, we present two canonical constructions
yielding a formal framework where models denote modules
with state and mixins, respectively, and we define a
set of primitive operations over them. },
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/PhDthesis.ps.gz},
keywords = {semantics, components, objects},
number = {TD-1/98},
year = 1998
}
@inproceedings{AZ-PLILP97,
author = {D.~Ancona and E.~Zucca},
title = {Overriding Operators in a Mixin-Based Framework},
booktitle = {P{LILP} '97 - 9th {I}ntl. {S}ymp. on {P}rogramming
{L}anguages, {I}mplementations, {L}ogics, and
{P}rograms},
editor = {H.~Glaser and P.~Hartel and H.~Kuchen},
volume = {1292},
series = {Lecture Notes in Computer Science},
pages = {47--61},
publisher = {Springer Verlag},
abstract = {We show that many different overriding operators
present in programming languages can be expressed,
adopting a mixin-based framework, in terms of three
basic operators. In particular we propose two
orthogonal classifications: strong (the overridden
definition is canceled) or weak (the overridden
definition still remains significant, as in Smalltalk's
super feature), and preferential (priority to one of
the two arguments) or general. We formalize the
relation between all these versions. Our analysis and
results are not bound to a particular language, since
they are formulated within an algebraic framework for
mixin modules which can be instantiated over different
core languages.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/PLILP97.ps.gz},
keywords = {semantics, objects, components},
year = 1997
}
@inproceedings{AAZ-ISCORE93,
author = {D. Ancona and E. Astesiano and E. Zucca},
title = {Towards a Classification of Inheritance Relations},
booktitle = {Proc. {ISCORE} '93 ({I}nternational {W}orkshop on
{I}nformation {S}ystems - {C}orrectness and
{R}eusability)},
editor = {U.W. Lipeck and G. Koschorreck},
number = {01/93},
series = {Informatik-Berichte},
pages = {90--113},
publisher = {Universitaet Hannover},
abstract = {We address the problem of providing a rigorous formal
model for classes of objects and the variety of
inheritance relations. Classes are modelled by a new
structure, called d-oid, which corresponds to see
objects as data with state. The approach we take is a
rather abstract one and so we model representation
independent configurations of an object system by
algebras, object identities by so called tracking map,
and method calls as transformations of algebras. Seeing
classes as d-oids allows us to define a hierarchy of
inheritance relations, modelled by relations between
d-oids and corresponding to different liberty levels in
redefining methods. The classification we present
distinguish essentially three levels of inheritance:
minimal, regular and conservative.},
ftp = {ftp://ftp.disi.unige.it/pub/person/AnconaD/IWIS93.ps.gz},
keywords = {semantics, objects},
year = 1993
}
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