Tuning the Level of Concurrency in Software Transactional Memory: An Overview of Recent Analytical, Machine Learning and Mixed Approaches

Synchronization transparency offered by Software Transactional Memory (STM) must not come at the expense of run-time efficiency, thus demanding from the STM-designer the inclusion of mechanisms properly oriented to performance and other quality indexes. Particularly, one core issue to cope with in STM is related to exploiting parallelism while also avoiding thrashing phenomena due to excessive transaction rollbacks, caused by excessively high levels of contention on logical resources, namely concurrently accessed data portions. A means to address run-time efficiency consists in dynamically determining the best-suited level of concurrency (number of threads) to be employed for running the application (or specific application phases) on top of the STM layer. For too low levels of concurrency, parallelism can be hampered. Conversely, over-dimensioning the concurrency level may give rise to the aforementioned thrashing phenomena caused by excessive data contention—an aspect which has reflections also on the side of reduced energy-efficiency. In this chapter we overview a set of recent techniques aimed at building “application-specific” performance models that can be exploited to dynamically tune the level of concurrency to the best-suited value. Although they share some base concepts while modeling the system performance vs the degree of concurrency, these techniques rely on disparate methods, such as machine learning or analytic methods (or combinations of the two), and achieve different tradeoffs in terms of the relation between the precision of the performance model and the latency for model instantiation. Implications of the different tradeoffs in real-life scenarios are also discussed

A compositional method for reliability analysis of workflows affected by multiple failure modes

We focus on reliability analysis for systems designed as workflow based compositions of components. Components are characterized by their failure profiles, which take into account possible multiple failure modes. A compositional calculus is provided to evaluate the failure profile of a composite system, given failure profiles of the components. The calculus is described as a syntax-driven procedure that synthesizes a workflows failure profile. The method is viewed as a design-time aid that can help software engineers reason about systems reliability in the early stage of development. A simple case study is presented to illustrate the proposed approach

A Model-Driven Approach for Business Process Management

The Business Process Management is a common mechanism recommended by a high number of standards for the management of companies and organizations. In software companies this practice is every day more accepted and companies have to assume it, if they want to be competitive. However, the effective definition of these processes and mainly their maintenance and execution are not always easy tasks. This paper presents an approach based on the Model-Driven paradigm for Business Process Management in software companies. This solution offers a suitable mechanism that was implemented successfully in different companies with a tool case named NDTQ-Framework.Ministerio de Educación y Ciencia TIN2010-20057-C03-02Junta de Andalucía TIC-578

Study on the use of metadata for digital learning objects in university institutional repositories (MODERI)

Metadata is a core issue for the creation of repositories. Different institutional repositories have chosen and use different metadata models, elements and values for describing the range of digital objects they store. Thus, this paper analyzes the current use of metadata describing those Learning Objects that some open higher educational institutions' repositories include in their collections. The goal of this work is to identify and analyze the different metadata models being used to describe educational features of those specific digital educational objects (such as audience, type of educational object, learning objectives, etc.). Also discussed is the concept and typology of Learning Objects (LO) through their use in University Repositories. We will also examine the usefulness of specifically describing those learning objects, setting them apart from other kind of documents included in the repository, mainly scholarly publications and research results of the Higher Education institution.En prens

Describing Scholarly Works with Dublin Core: A Functional Approach

This article describes the development of the Scholarly Works Application Profile (SWAP)—a Dublin Core application profile for describing scholarly texts. This work provides an active illustration of the Dublin Core Metadata Initiative (DCMI) “Singapore Framework” for Application Profiles, presented at the DCMI Conference in 2007, by incorporating the various elements of Application Profile building as defined by this framework—functional requirements, domain model, description set profile, usage guidelines, and data format. These elements build on the foundations laid down by the Dublin Core Abstract Model and utilize a preexisting domain model (FR-BR—Functional Requirements for Bibliographic Records) in order to support the representation of complex data describing multiple entities and their relationships. The challenges of engaging community acceptance and implementation will be covered, along with other related initiatives to support the growing corpus of scholarly resource types, such as data objects, geographic data, multimedia, and images whose structure and metadata requirements introduce the need for new application profiles. Finally, looking to other initiatives, the article will comment on how Dublin Core relates to the broader scholarly information world, where projects like Object Re-use and Exchange are attempting to better equip repositories to exchange resources

Distribution pattern-driven development of service architectures

Distributed systems are being constructed by composing a number of discrete components. This practice is particularly prevalent within the Web service domain in the form of service process orchestration and choreography. Often, enterprise systems are built from many existing discrete applications such as legacy applications exposed using Web service interfaces. There are a number of architectural configurations or distribution patterns, which express how a composed system is to be deployed in a distributed environment. However, the amount of code required to realise these distribution patterns is considerable. In this paper, we propose a distribution pattern-driven approach to service composition and architecting. We develop, based on a catalog of patterns, a UML-compliant framework, which takes existing Web service interfaces as its input and generates executable Web service compositions based on a distribution pattern chosen by the software architect