Four Lessons in Versatility or How Query Languages Adapt to the Web

Exposing not only human-centered information, but machine-processable data on the Web is one of the commonalities of recent Web trends. It has enabled a new kind of applications and businesses where the data is used in ways not foreseen by the data providers. Yet this exposition has fractured the Web into islands of data, each in different Web formats: Some providers choose XML, others RDF, again others JSON or OWL, for their data, even in similar domains. This fracturing stifles innovation as application builders have to cope not only with one Web stack (e.g., XML technology) but with several ones, each of considerable complexity. With Xcerpt we have developed a rule- and pattern based query language that aims to give shield application builders from much of this complexity: In a single query language XML and RDF data can be accessed, processed, combined, and re-published. Though the need for combined access to XML and RDF data has been recognized in previous work (including the W3C’s GRDDL), our approach differs in four main aspects: (1) We provide a single language (rather than two separate or embedded languages), thus minimizing the conceptual overhead of dealing with disparate data formats. (2) Both the declarative (logic-based) and the operational semantics are unified in that they apply for querying XML and RDF in the same way. (3) We show that the resulting query language can be implemented reusing traditional database technology, if desirable. Nevertheless, we also give a unified evaluation approach based on interval labelings of graphs that is at least as fast as existing approaches for tree-shaped XML data, yet provides linear time and space querying also for many RDF graphs. We believe that Web query languages are the right tool for declarative data access in Web applications and that Xcerpt is a significant step towards a more convenient, yet highly efficient data access in a “Web of Data”

Assessing the Effects of Mergers and Acquisitions on Firm Performance, Plant Productivity, and Workers: New Evidence from Matched Employer-Employee Data

Studies of the effects of mergers and acquisitions focus on a single unit of analysis: firms, plants, or workers. In contrast, we model these events as transactions that simultaneously have cross-levels effects. Based on the theory of human capital, we generate a set of predictions regarding the antecedents and consequences of firm, plant, and worker turnover. Our empirical analysis is based on longitudinal, linked employer-employee data for virtually the entire population of Swedish manufacturing firms and employees for the period 1985-1998. These data allow us to assess the effects of mergers and acquisitions on firm performance, plant productivity, levels of employment, and compensation. Consistent with human capital theory, we find that mergers and acquisitions lead to improvements in firm performance and plant productivity, although they also result in the downsizing of establishments and firms. These transactions also appear to enhance the careers of workers because they provide a mechanism for improving the sorting and matching or workers and managers to firms and industries that best suit their skills.

Before-Commit Client State Management Services for AJAX Applications

Heavily script-based browser applications change the manner in which users interact with Web browsers. Instead of downloading a succession of HTML pages, users download a single application and use that application for a long period of time. The application is not a set of HTML pages, but rather a single page that can possible modify its own presentation based on data exchanged with a server. In such an environment, it is necessary to provide some means for the client to manage its own state. We describe the initial results of our work in providing client-side state management services for these script-based applications. We focus on browser-based services that can help the user before any data is committed on the server. Our services include state checkpointing, property binding, operation logging, operational replay, ATOM/RSS data updates, and application-controlled persistence

Security for Cloud Environment through Information Flow Properties Formalization with a First-Order Temporal Logic

The main slowdown of Cloud activity comes from the lack of reliable security. The on-demand security concept aims at delivering and enforcing the client's security requirements. In this paper, we present an approach, Information Flow Past Linear Time Logic (IF-PLTL), to specify how a system can support a large range of security properties. We present in this paper how to control those information flows from lower system events. We give complete details over IF-PLTL syntax and semantics. Furthermore, that logic enables to formalize a large set of security policies. Our approach is exemplified with the Chinese Wall commercial-related policy. Finally, we discuss the extension of IF-PLTL with dynamic relabeling to encompass more realistic situations through the dynamic domains isolation policy.La principale cause de ralentissement de l'adoption du Cloud est le manque de sécurité fiable. Le concept de sécurité à la demande est de déployer et d'appliquer les demandes de sécurité d'un client. Dans ce papier, nous présentons une approche, Information Flow Past Linear Time Logic (IF-PLTL), qui permet de spécifier comment un système peut supporter un large ensemble de propriétés de sécurité. Nous présentons dans ce papier comment ces flux d'information peuvent être contrôler en utilisant les événements systèmes de bas niveau. Nous donnons une description compléte de la syntaxe de IF-PLTL ainsi que sa sémantique. De plus, cette logique permet de formaliser un large ensemble de politiques de sécurité. Notre approche est illustrée par la politique de sécurité de la muraille de Chine orienté vers le monde commercial. Finalement, nous montrons comment nous avons étendu notre langage pour supporter la relabélisation dynamique qui permet de supporter la dynamicité inhérante des systèmes. Nous illustrons cette extension par la formalisation d'une propriété de sécurité pour l'isolation dynamique de domaines

Sector Switching: An Unexplored Dimension of Firm Dynamics in Developing Countries

Much of the literature on industry evolution has found firm dynamics to be an important source of sector-level productivity growth. In this paper, we ask whether the delineation of entry and exit firms matters in assessing the impact of firm turnover. Using detailed firm level data from Vietnam, it emerges that efficiency differences between sector switchers and exit/entry firms exist. Distinguishing between switchers and firm entry/exit is crucial for understanding the contribution of firm turnover to overall productivity growth. Moreover, we uncover distinct and illuminating firm and sector-level determinants of firm exit and switching, which need to be carefully considered in the search for effective policy.

Sector Switching: An Unexplored Dimension of Firm Dynamics in Developing Countries

Much of the literature on industry evolution has found firm dynamics to be an important source of sector-level productivity growth. In this paper, we ask whether the delineation of entry and exit firms matters in assessing the impact of firm turnover. Using detailed firm level data from Vietnam, it emerges that efficiency differences between sector switchers and exit/entry firms exist. Distinguishing between switchers and firm entry/exit is crucial for understanding the contribution of firm turnover to overall productivity growth. Moreover, we uncover distinct and illuminating firm and sector-level determinants of firm exit and switching, which need to be carefully considered in the search for effective policy.firm dynamics; sector switching; efficiency; Vietnam

Sector Switching: An Unexplored Dimension of Firm Dynamics in Developing Countries

Much of the literature on industry evolution has found firm dynamics to be an important source of sector-level productivity growth. In this paper, we ask whether the delineation of entry and exit firms matters in assessing the impact of firm turnover. Using detailed firm level data from Vietnam, it emerges that efficiency differences between sector switchers and exit/entry firms exist. Distinguishing between switchers and firm entry/exit is crucial for understanding the contribution of firm turnover to overall productivity growth. Moreover, we uncover distinct and illuminating firm and sector-level determinants of firm exit and switching, which need to be carefully considered in the search for effective policy.Firm dynamics, sector switching, efficiency, Vietnam