Open Multithreaded Transactions: A Transaction Model for Concurrent Object-Oriented Programming

To read the abstract, please go to my PhD home page

Exception Handling in Open Multithreaded Transactions

This paper describes a model for providing transaction support for object-oriented concurrent programming languages. In order to achieve seamless integration, the use of the concurrency features provided by the programming language should not be restricted inside a transaction. A transaction model that meets this requirement is presented. Threads inside such a transaction may spawn new threads, but also external threads are allowed to join an ongoing transaction. A blocking commit protocol ensures that no thread leaves the transaction before its outcome has been determined. Exceptions are used to inform all participants in case a transaction aborts

Combining Tasking and Transactions, Part II: Open Multithreaded Transactions

This position paper is a follow-up paper of the one presented at the last IRTAW workshop. The paper describes a model for providing transaction support for concurrent programming languages such as Ada 95. In order to achieve smooth integration, the use of the concurrency features provided by the Ada language should not be restricted inside a transaction. A transaction model that meets this requirement is presented. Tasks inside such a transaction may spawn new tasks, but also external tasks are allowed to join an ongoing transaction. A blocking commit protocol ensures that no task leaves the transaction before its outcome has been determined. Exceptions are used to inform all participants in case a transaction aborts. The design of a library that provides support for the transaction model is presented, and possible interfaces for the Ada programmer are discussed

Object Persistence: A Framework Based On Design Patterns

The poster presents a framework for providing object persistence in object-oriented programming languages without modifying the run-time system or the language itself. The framework does not rely on any kind of special programming language features. It only uses basic object-oriented programming techniques, and is therefore implementable in any object-oriented programming language

AOP: Does it Make Sense ? The Case of Concurrency and Failures

Concurrency and failures are fundamental problems in distributed computing. One likes to think that the mechanisms needed to address these problems can be separated from the rest of the distributed application: in modern words, these mechanisms could be aspectized. Does this however make sense? This paper relates an experience that conveys our initial and indeed biased intuition that the answer is in general no. Except for simple academic examples, it is hard and even potentially dangerous to separate concurrency control and failure management from the actual application. We point out the very facts that (1) an aspect-oriented language can, pretty much like a macro language, be beneficial for code factorization (but should be reserved to experienced programmers), and (2) concurrency and failures are particularly hard to aspectize because they are usually part of the phenomenon that objects should simulate. They are in this sense different than other concerns, like for instance tracing, which might be easier to aspectize

On Persistent and Reliable Streaming in Ada

Saving internal program data for further use is one of the most useful ideas in programming. Developing general features to provide such data saving/restoring is a very active research area. There are two application areas for such features we believe to be crucial: system fault tolerance and data persistence. Our analysis shows that the features used in these areas have a lot in common: they are to flatten data of different types and save them in a store which can be used later on. The recent revision of the Ada language standard, Ada 95, introduces a new mechanism called streams that allows structured data to be flattened. Streams are sequences of elements comprising values from possibly different types. Ada 95 allows programmers to develop their streams following the standard abstract class interface. In this paper we show how to use the stream concept for developing new features to provide internal program data saving suitable for fault tolerance and persistence. A hierarchy of different storage types, useful in different application domains, is introduced. The standard stream interface is extended, making it possible for programmers to have a better control of the way streams work by separating storage medium control from the actual stream type using the design patterns. The convenience of this new interface is demonstrated by developing a generic package allowing any non-limited object to be written into a storage device. It can be used for providing data persistence and as a state restoration feature in schemes used for tolerating software design faults

Facet-oriented Modelling

© ACM 2021. This is the author's version of the work. It is posted here for your personal use. Not for redistribution. The definitive Version of Record was published in ACM Transactions on Software Engineering and Methodology, http://dx.doi.org/10.1145/10.1145/3428076Models are the central assets in model-driven engineering (MDE), as they are actively used in all phases of software development. Models are built using metamodel-based languages, and so objects in models are typed by a metamodel class. This typing is static, established at creation time, and cannot be changed later. Therefore, objects in MDE are closed and fixed with respect to the class they conform to, the fields they have, and the well-formedness constraints they must comply with. This hampers many MDE activities, like the reuse of model-related artefacts such as transformations, the opportunistic or dynamic combination of metamodels, or the dynamic reconfiguration of models. To alleviate this rigidity, we propose making model objects open so that they can acquire or drop so-called facets. These contribute with a type, fields and constraints to the objects holding them. Facets are defined by regular metamodels, hence being a lightweight extension of standard metamodelling. Facet metamodels may declare usage interfaces, as well as laws that govern the assignment of facets to objects (or classes). This article describes our proposal, reporting on a theory, analysis techniques, and an implementation. The benefits of the approach are validated on the basis of five case studies dealing with annotation models, transformation reuse, multi-view modelling, multi-level modelling, and language product linesWork partially funded by the R&D programme of the Madrid Region (project FORTE, S2018/TCS-4314) and the Spanish Ministry of Science (project MASSIVE, RTI2018-095255-B-I00

A Framework Based on Design Patterns for Providing Persistence in Object-Oriented Programming Languages

This paper describes an approach to providing object persistence in object-oriented programming languages without modifying the run-time system or the language itself. By successively applying design patterns such as the Serializer, Factory Method, and Strategy patterns we develop an object-oriented framework for providing object persistence. The advantages of object-orientation are highlighted: structured classification through class-hierarchies, extensibility and promotion of reuse. The framework clearly separates persistence control from storage control. A hierarchy of different storage types, useful in different application domains, is introduced. The framework does not rely on any kind of special programming language features. It only uses basic object-oriented programming techniques, and is therefore implementable in any object-oriented programming language. An experimental implementation in Ada 95 is presented

Open Multithreaded Transactions: Keeping Threads and Exceptions under Control

Although transactional models have proved to be very useful for numerous applications, the development of new models to reflect the ever-increasing complexity and diversity of modern applications is a very active area of research. Analysis of the existing models of multithreaded transactions shows that they either give too much freedom to threads and do not control their participation in transactions, or unnecessarily restrict the computational model by assuming that only one thread can enter a transaction. Another important issue, which many models do not address properly, is providing adequate exception handling features. In this paper a new model of multithreaded transactions is proposed. Its detailed description is given, including rules of thread behaviour when transactions start, commit and abort, and rules of exception raising, propagation and handling. This model is supported by enhanced error detection techniques to allow for earlier error detection and for localised recovery. General approaches to implementing transaction support are discussed and a detailed description of an Ada implementation is given. Special attention is paid to outlining typical applications for which this model is suitable and to comparing it with several known approaches (Coordinated Atomic actions, CORBA, and Argus)

Porting OMTTs to CORBA

The Common Object Request Broker Architecture standardizes a platform- and programming-language-independent distributed object com-puting environment. It also provides a standard for several distributed servic-es. The Object Transaction Service provides an object-oriented framework for distributed transaction processing, especially for Online Transaction Pro-cessing in business applications. The current CORBA OTS allows multi-threading inside a transaction, leaving, however, thread coordination to the application programmer, which can be dangerous. Based on the Open Multi-threaded Transaction model, we present in this paper the design of a Thread Synchronization Coordinator, ThreadSyncCoordinator, which provides the desired thread control inside a multithreaded transaction. A blocking commit protocol ensures that once in a transaction, a thread cannot leave before the outcome of the transaction has been determined, guaranteeing the ACID properties for multithreaded transactions. We also show how the Thread-SyncCoordinator can be used to design and implement complex applications, e.g., an Online Auction System, in an elegant way