Class-based Model Research Articles

Explaining Peasant-Farmer Hegemony in Redistributive Politics: Class-, Trade-, and Asset-Based Approaches

What are the most important cleavages created by political struggles over redistributive economic policies? What are the likely policy outcomes of these struggles? The classic answer to the first question is that the most important cleavage is that of class, dividing rich and poor. The class-based model is usually not taken to yield clear predictions about outcomes, because rich and poor would be expected to engage in an inconclusive bidding war for the support of the median voter or pivotal middle stratum. A more recent answer is that the most important cleavages will reflect the position of a given country in the international economy, pitting those benefiting from international trade against those hurt by it. This trade-based model yields stronger predictions about outcomes, since there is usually a clear majority that either does or does not benefit from international trade. Finally, there is a long, though loose, tradition that largely grows out of empirical observation. This emphasizes the pivotal role that the agricultural population appears to play in the more important political battles concerning institutional development and economic policy.

Optimizing channel allocation in a unified video-on-demand system

Unified video-on-demand (UVoD) is an architecture that integrates multicast transmission with unicast transmission to improve system efficiency. Streaming channels in a UVoD system are divided into unicast and multicast channels, with the multicast channels further divided equally among all videos. This uniform channel-allocation scheme is simple to design and implement, but the performance may not be optimal due to differences in video popularity. This paper investigates this channel-allocation problem with the goal of optimizing system efficiency. First, the uniform allocation assumption is removed and the channel-allocation problem formulated as a nonlinear integer optimization problem. This optimization model results in nonuniform channel allocations that can save up to 10% of channels. Second, to reduce the computational complexity in solving the nonlinear optimization model, an approximate model is derived and solved under small-latency conditions to obtain a closed-form solution. Third, a much simpler class-based popularity model is proposed and shown to achieve good efficiency, even if the precise popularity of each video is not known. Lastly, a zero-multicast channel-optimization algorithm is introduced that can further reduce channel requirement for systems with a large number of video selections. Numerical results show that optimized nonuniform channel-allocation policies can achieve channel reduction over uniform channel allocation by as much as 50% for a 1000-video system.

The Analysis and Performance of Multi-Rate Service in Distributed Video-on-Demand Systems

In this paper, we develop an end-to-end analysis of a distributed Video-on-Demand (VoD) system that includes an integrated model of the server and the network subsystems with analysis of its impact on client operations. The VoD system provides service to a heterogeneous client base at multiple playback rates. A class-based service model is developed where an incoming video request can specify a playback rate at which the data is consumed on the client. Using an analytical model, admission control conditions at the server and the network are derived for multi-rate service. We also develop client buffer requirements in presence of network delay bounds and delay jitter bounds using the same integrated framework of server and network subsystems. Results from an extensive simulation show that request handling policies based on limited redirection of blocked requests to other resources perform better than load sharing policies. The results also show that downgrading the service for blocked requests to a lower bitrate improves VoD system performance considerably. Combining the downgrade option with restrictions on access to high bitrate request classes is a powerful tool for manipulating an incoming request mix into a workload that the VoD system can handle.

The Politics of Retrenchment in a Social Democratic Welfare State

What explains the origins and pattern of retrenchment dynamics in Swedish old-age pensions and unemployment insurance during the 1990s? Although the economic crisis created pressure to scale back both programs, the author argues that retrenchment only occurred when and where the Social Democratic Party and some segments of the labor movement supported change. This finding suggests that the political importance of organized labor in retrenchment politics depends on the relationship between welfare-state programs and interest group structure. When interest group structure is characterized by solidaristic, centralized, encompassing organizations, the old class-based power resource model has more explanatory bite than Pierson's new politics of the welfare-state approach.

Using differentiated services to support Internet telephony

Internet telephony has been deemed as a promising candidate for the next generation telephone system. However, unstable voice quality is the main problem that prevents the Internet Telephone from competing with the traditional circuit switched telephone. Current Internet supports only a best-effort service class, which does not provide any bandwidth or delay guarantee for the voice packets. During congestion, consecutive packets get lost or miss the deadlines, which results in severe degradation in voice quality. In this paper, we introduce the concept of using differentiated service model to solve the problem. First, we propose a class-based model to separate the voice streams from the best-effort traffic. Then we use a selective dropping model to further prevent consecutive packet losses to satisfy the ( m, k) firm guarantee [9] requirement, and thereby enhance the voice quality in the Internet telephony services. The model is implemented using the ns simulator [18]. The performance of the proposed technique is evaluated through the simulator and the results justify the validity of using the model for Internet telephony.

Object-oriented systems: a cross-discipline overview

The object-oriented paradigm is characterized in a general sense by a grouping of information with the concept or entity to which it relates. Corresponding to this rather vague definition, there is a wide range of systems that can be classified as object-oriented. However, such systems may provide significantly different perspectives on the structure and manipulation of objects. This stems principally from the different motivations underlying the distinct fields from which object-oriented systems have emerged, such as Data Bases, Artificial Intelligence and Programming Languages. As a result, a myriad of systems have appeared in which diverse terminology is used. For example, are terms such as class, frame, term, actor and entity synonyms, related notions, or descriptions of distinct concepts? How is an object different from these terms? This paper proposes a classification of object-oriented systems based upon the conceptualization underlying an object and how such a conceptualization is described. Hence, the issue is more on modelling with objects rather than system idiosyncrasies. Four broad families are identified depending on whether systems follows either a class-based model, a frame-based model, a terminological model or an actor-based model. In the paper, for each category, a definition of the conceptualization is first presented, followed by a description of its characteristics together with some examples of its intended use. The classification serves both as a framework for comparison and as a context within which individual concepts can be described.

Evaluation of a class-based storage scheduling technique applied to dual-shuttle automated storage and retrieval systems

Abstract Research to improve the performance of automated storage and retrieval systems has concentrated on developing more effective system designs or scheduling control programs to reduce the time a shuttle spends travelling in a rack. Sarker et al. (1991) showed that a dual-shuttle AS/RS operating under a nearest-neighbour scheduling model would significantly improve system throughput performance over a single-load shuttle system. The study was limited in that it only considered dual-shuttle improvements under the nearest-neighbour model. This research exploits the benefits of a dual-shuttle system by integrating the technology with a more effective scheduling technique, the class-based storage model, for reducing the shuttle travel time. The dual-shuttle, class-based storage model produced a significant reduction in shuttle travel time and thus higher throughput results over the dual-shuttle, nearest-neighbour model. This study further supports the premise that a dual-capacity shuttle is an effective ...

Rosette: An object-oriented concurrent systems architecture

A number of concurrent computers have been designed, such as [Ametek 1988] and [NCUBE 1986]. Taking advantage of concurrency on these computers will require new languages, operating systems, and en...