1,686 research outputs found
Typing Copyless Message Passing
We present a calculus that models a form of process interaction based on
copyless message passing, in the style of Singularity OS. The calculus is
equipped with a type system ensuring that well-typed processes are free from
memory faults, memory leaks, and communication errors. The type system is
essentially linear, but we show that linearity alone is inadequate, because it
leaves room for scenarios where well-typed processes leak significant amounts
of memory. We address these problems basing the type system upon an original
variant of session types.Comment: 50 page
Modular session types for objects
Session types allow communication protocols to be specified
type-theoretically so that protocol implementations can be verified by static
type checking. We extend previous work on session types for distributed
object-oriented languages in three ways. (1) We attach a session type to a
class definition, to specify the possible sequences of method calls. (2) We
allow a session type (protocol) implementation to be modularized, i.e.
partitioned into separately-callable methods. (3) We treat session-typed
communication channels as objects, integrating their session types with the
session types of classes. The result is an elegant unification of communication
channels and their session types, distributed object-oriented programming, and
a form of typestate supporting non-uniform objects, i.e. objects that
dynamically change the set of available methods. We define syntax, operational
se-mantics, a sound type system, and a sound and complete type checking
algorithm for a small distributed class-based object-oriented language with
structural subtyping. Static typing guarantees that both sequences of messages
on channels, and sequences of method calls on objects, conform to
type-theoretic specifications, thus ensuring type-safety. The language includes
expected features of session types, such as delegation, and expected features
of object-oriented programming, such as encapsulation of local state.Comment: Logical Methods in Computer Science (LMCS), International Federation
for Computational Logic, 201
Session Types as Generic Process Types
Behavioural type systems ensure more than the usual safety guarantees of
static analysis. They are based on the idea of "types-as-processes", providing
dedicated type algebras for particular properties, ranging from protocol
compatibility to race-freedom, lock-freedom, or even responsiveness. Two
successful, although rather different, approaches, are session types and
process types. The former allows to specify and verify (distributed)
communication protocols using specific type (proof) systems; the latter allows
to infer from a system specification a process abstraction on which it is
simpler to verify properties, using a generic type (proof) system. What is the
relationship between these approaches? Can the generic one subsume the specific
one? At what price? And can the former be used as a compiler for the latter?
The work presented herein is a step towards answers to such questions.
Concretely, we define a stepwise encoding of a pi-calculus with sessions and
session types (the system of Gay and Hole) into a pi-calculus with process
types (the Generic Type System of Igarashi and Kobayashi). We encode session
type environments, polarities (which distinguish session channels end-points),
and labelled sums. We show forward and reverse operational correspondences for
the encodings, as well as typing correspondences. To faithfully encode session
subtyping in process types subtyping, one needs to add to the target language
record constructors and new subtyping rules. In conclusion, the programming
convenience of session types as protocol abstractions can be combined with the
simplicity and power of the pi-calculus, taking advantage in particular of the
framework provided by the Generic Type System.Comment: In Proceedings EXPRESS/SOS 2014, arXiv:1408.127
Dynamic Role Authorization in Multiparty Conversations
Protocol specifications often identify the roles involved in communications.
In multiparty protocols that involve task delegation it is often useful to
consider settings in which different sites may act on behalf of a single role.
It is then crucial to control the roles that the different parties are
authorized to represent, including the case in which role authorizations are
determined only at runtime. Building on previous work on conversation types
with flexible role assignment, here we report initial results on a typed
framework for the analysis of multiparty communications with dynamic role
authorization and delegation. In the underlying process model, communication
prefixes are annotated with role authorizations and authorizations can be
passed around. We extend the conversation type system so as to statically
distinguish processes that never incur in authorization errors. The proposed
static discipline guarantees that processes are always authorized to
communicate on behalf of an intended role, also covering the case in which
authorizations are dynamically passed around in messages.Comment: In Proceedings BEAT 2014, arXiv:1408.556
A Systematic Aspect-Oriented Refactoring and Testing Strategy, and its Application to JHotDraw
Aspect oriented programming aims at achieving better modularization for a
system's crosscutting concerns in order to improve its key quality attributes,
such as evolvability and reusability. Consequently, the adoption of
aspect-oriented techniques in existing (legacy) software systems is of interest
to remediate software aging. The refactoring of existing systems to employ
aspect-orientation will be considerably eased by a systematic approach that
will ensure a safe and consistent migration.
In this paper, we propose a refactoring and testing strategy that supports
such an approach and consider issues of behavior conservation and (incremental)
integration of the aspect-oriented solution with the original system. The
strategy is applied to the JHotDraw open source project and illustrated on a
group of selected concerns. Finally, we abstract from the case study and
present a number of generic refactorings which contribute to an incremental
aspect-oriented refactoring process and associate particular types of
crosscutting concerns to the model and features of the employed aspect
language. The contributions of this paper are both in the area of supporting
migration towards aspect-oriented solutions and supporting the development of
aspect languages that are better suited for such migrations.Comment: 25 page
A type system for components
In modern distributed systems, dynamic reconfiguration, i.e.,
changing at runtime the communication pattern of a program, is chal-
lenging. Generally, it is difficult to guarantee that such modifications will
not disrupt ongoing computations. In a previous paper, a solution to this
problem was proposed by extending the object-oriented language ABS
with a component model allowing the programmer to: i) perform up-
dates on objects by means of communication ports and their rebinding;
and ii) precisely specify when such updates can safely occur in an object
by means of critical sections. However, improper rebind operations could
still occur and lead to runtime errors. The present paper introduces a
type system for this component model that extends the ABS type system
with the notion of ports and a precise analysis that statically enforces
that no object will attempt illegal rebinding
A Historical Perspective on Runtime Assertion Checking in Software Development
This report presents initial results in the area of software testing and analysis produced as part of the Software Engineering Impact Project. The report describes the historical development of runtime assertion checking, including a description of the origins of and significant features associated with assertion checking mechanisms, and initial findings about current industrial use. A future report will provide a more comprehensive assessment of development practice, for which we invite readers of this report to contribute information
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