Cyclical Dependencies Research Articles

Finding the Transitive Closure of Functional Dependencies using Strategic Port Graph Rewriting

We present a new approach to the logical design of relational databases, based on strategic port graph rewriting. We show how to model relational schemata as attributed port graphs and provide port graph rewriting rules to perform computations on functional dependencies. Using these rules we present a strategic graph program to find the transitive closure of a set of functional dependencies. This program is sound, complete and terminating, assuming that there are no cyclical dependencies in the schema.

Theories of Poverty: A Critical Review

The study reviewed literature on the theories of poverty. The theories reviewed included theory of individual deficiencies, theory of cultural beliefs, theory of economic, political and social distortions, theory of geographical disparities, and theory of cumulative and cyclical dependencies. The theories were analysed, criticised and measures that will bring the poor out of poverty were recommended. Some of the recommended solutions included: encouraging the poor to embrace self-help strategies, replacing the culture with one that encourages hard work and investment, changing the system for the better, improving infrastructure and local industries competitiveness, and developing comprehensive programmes that will help the poor to be self-sufficient. Key words: Poverty, Cultural beliefs, Individual deficiencies, Geographical disparities, Economic, political, and structural f actors, psychological theories, sociological theories. DOI : 10.7176/JPID/48-08

On the goodput of flows in heterogeneous mobile networks

In practice heterogeneous networks comprising of diverse nodes need to operate efficiently under a wide range of node mobility and link quality regimes. In this paper, we propose algorithms to determine the goodput of flows in heterogeneous mobile networks. We consider a scenario where some network nodes operate as routers while others operate as flooders, based on the underlying forwarding policy. When a node operates as a router, it forwards packets based on the routing table as determined by the underlying routing algorithm and when it operates as a flooder, it broadcasts packets to all its neighbors. We begin with the case of a single network flow and demonstrate that the problem of determining the goodput is challenging even for this simple setting. We construct a Bayesian network, and propose an algorithm based on the sum-product algorithm to determine the exact goodput. We extend the proposed Bayesian network model for exact goodput calculation to feed forward networks with multiple flows. For a general network with multiple flows, the problem becomes more challenging. The difficulty of the problem stems from the fact that node pairs can forward traffic to one another, resulting in cyclical dependencies. We propose a fixed-point approximation to determine the goodput in this case. Finally, we present an application scenario, where we leverage the fixed-point approximation to design a forwarding strategy adaptive-flood that adapts seamlessly to varying networking conditions. We perform simulations and show that adaptive-flood can effectively classify individual nodes as routers/flooders, achieving performance equivalent to, and in some cases significantly better than that of network-wide routing or flooding alone.

Causal Theories of Actions Revisited

It has been argued that causal rules are necessary for representing both implicit side-effects of actions and action qualifications, and there have been a number different approaches for representing causal rules in the area of formal theoriesof actions. These different approaches in general agree on rules without cycles. However, they differ on causal rules with mutual cyclic dependencies, both in terms of how these rules are supposed to be represented and their semantics. In this paper we show that by adding one more minimization to Lin's circumscriptive causal theory in the situation calculus, we can have a uniform representation of causal rules including those with cyclic dependencies. We also demonstrate that sometimes causal rules can be compiled into logically equivalent successor state axioms even in the presence of cyclical dependencies between fluents.

Product Architecture and Quality: A Study of Open-Source Software Development

We examine how the architecture of products relates to their quality. Using an architectural representation that accounts for both the hierarchical and dependency relationships between modules and components, we define a new construct, system cyclicality. System cyclicality recognizes component loops, which are akin to design iterations — a concept typically associated with models of product development processes rather than the products themselves. System cyclicality captures the fraction of mutually interdependent components in a system. Through a multilevel analysis of several open-source, Java-based applications developed by the Apache Software Foundation, we study the relationship between system cyclicality and the generation of bugs. At the system level, we examine 122 releases representing 19 applications and find that system cyclicality is positively associated with the number of bugs in a system. At the component level, we examine 28,395 components and find that components involved in loops are likely to be affected by a larger number of bugs. We find that, in order to identify the set of product components involved in cyclical dependencies that are detrimental to product quality, it is imperative to remove from consideration the architectural decisions by which components are assigned into modules: it is necessary to focus only on the patterns of dependencies among product components without considering how components are grouped together into modules. Our results suggest that new product development managers are likely to benefit from proactively examining the architecture of the system they develop and monitoring its cyclicality as one of their strategies to reduce defects.

Postroute Gate Sizing for Crosstalk Noise Reduction

Gate sizing is a practical and a feasible crosstalk noise correction technique in the post route design stage, especially for block level sea-of-gates designs. The difficulty in gate sizing for noise reduction is that, by increasing a driver size, noise at the driver output is reduced, but noise injected by that driver on other nets is increased. This can create cyclical dependencies between nets in the circuit with noise violations. In this paper, we propose a fast and effective heuristic postroute gate-sizing algorithm that uses a graph representation of the noise dependencies between nodes. Our method utilizes gate sizing in both directions and works in linear time as a function of the number of gates. The effectiveness of the algorithm is shown on several industrial high-performance designs.