Minimizing and Computing the Inverse Geodesic Length on Trees

For any fixed measure H that maps graphs to real numbers, the MinH problem is defined as follows: given a graph G, an integer k, and a target tau, is there a set S of k vertices that can be deleted, so that H(G - S) is at most tau? In this paper, we consider the MinH problem on trees. We call H balanced on trees if, whenever G is a tree, there is an optimal choice of S such that the components of G - S have sizes bounded by a polynomial in n / k. We show that MinH on trees is Fixed-Parameter Tractable (FPT) for parameter n / k, and furthermore, can be solved in subexponential time, and polynomial space, whenever H is additive, balanced on trees, and computable in polynomial time. A particular measure of interest is the Inverse Geodesic Length (IGL), which is used to gauge the efficiency and connectedness of a graph. It is defined as the sum of inverse distances between every two vertices: IGL(G) = sum_{{u,v} subseteq V} 1/d_G(u,v). While MinIGL is W[1]-hard for parameter treewidth, and cannot be solved in 2^{o(k + n + m)} time, even on bipartite graphs with n vertices and m edges, the complexity status of the problem remains open in the case where G is a tree. We show that IGL is balanced on trees, to give a 2^O((n log n)^(5/6)) time, polynomial space algorithm. The distance distribution of G is the sequence {a_i} describing the number of vertex pairs distance i apart in G: a_i = |{{u, v}: d_G(u, v) = i}|. Given only the distance distribution, one can easily determine graph parameters such as diameter, Wiener index, and particularly, the IGL. We show that the distance distribution of a tree can be computed in O(n log^2 n) time by reduction to polynomial multiplication. We also extend the result to graphs with small treewidth by showing that the first p values of the distance distribution can be computed in 2^(O(tw(G))) n^(1 + epsilon) sqrt(p) time, and the entire distance distribution can be computed in 2^(O(tw(G))) n^{1 + epsilon} time, when the diameter of G is O(n^epsilon\u27) for every epsilon\u27 > 0

Algorithms and Hardness for Multidimensional Range Updates and Queries

Traditional orthogonal range problems allow queries over a static set of points, each with some value. Dynamic variants allow points to be added or removed, one at a time. To support more powerful updates, we introduce the Grid Range class of data structure problems over arbitrarily large integer arrays in one or more dimensions. These problems allow range updates (such as filling all points in a range with a constant) and queries (such as finding the sum or maximum of values in a range). In this work, we consider these operations along with updates that replace each point in a range with the minimum, maximum, or sum of its existing value, and a constant. In one dimension, it is known that segment trees can be leveraged to facilitate any n of these operations in O?(n) time overall. Other than a few specific cases, until now, higher dimensional variants have been largely unexplored. Despite their tightly-knit complexity in one dimension, we show that variants induced by subsets of these operations exhibit polynomial separation in two dimensions. In particular, no truly subquadratic time algorithm can support certain pairs of these updates simultaneously without falsifying several popular conjectures. On the positive side, we show that truly subquadratic algorithms can be obtained for variants induced by other subsets. We provide two general approaches to designing such algorithms that can be generalised to online and higher dimensional settings. First, we give almost-tight O?(n^{3/2}) time algorithms for single-update variants where the update and query operations meet a set of natural conditions. Second, for other variants, we provide a general framework for reducing to instances with a special geometry. Using this, we show that O(m^{3/2-?}) time algorithms for counting paths and walks of length 2 and 3 between vertex pairs in sparse graphs imply truly subquadratic data structures for certain variants; to this end, we give an O?(m^{(4?-1)/(2?+1)}) = O(m^1.478) time algorithm for counting simple 3-paths between vertex pairs

KK-theory of co-existentially closed continua

We describe the possible values of $K$-theory for $C(X)$ when $X$ is a co-existentially closed continuum. As a consequence we also show that all pseudo-solenoids, except perhaps the universal one, are not co-existentially closed.Comment: 15 page

An Ontology-based Collaborative Knowledge Management Network to Enhance the Reusability of Inter-organizational Knowledge

A number of knowledge management (KM) approaches based on individual organizational KM strategies and business requirements have been developed without taking system interoperation into consideration. In this paper, a collaborative inter-organizational KM network is proposed to allow various organizations to access and retrieve inter-organizational knowledge. While knowledge engineers can reuse the inter-organizational knowledge to create and evaluate its own organizational knowledge, general users benefit from the effectiveness and efficiency of searching for relevant inter-organizational knowledge within the networ

Environmental justice in coastal systems: perspectives from communities confronting change

Life in the Pacific is characterised by interconnected, fast and slow socio-ecological change. These changes inevitably involve navigating questions of justice, as they shift who benefits from, owns, and governs resources, and whose claims and rights are recognized. Thus, greater understanding of perceptions of environmental justice within communities will be crucial to support fair adaptation. We contend that an environmental justice approach offers a theoretical foundation to help illuminate key concerns and trade-offs as communities navigate global change. Here, we apply an empirical environmental justice lens to the use and customary management of coastal resources in Papua New Guinea. Through two case studies, we examine perceptions of distributional, procedural and recognitional justice. We find similarities and differences. There were common concerns about the injustice of unequal fishing pressure and destructive methods, but in one case, concerns about people’s material needs overrode concerns about non-compliance and unequal costs. In the other case, deliberative decision-making served as a platform for not only negotiating and re-defining the distribution of costs and benefits, but also airing grievances, thereby strengthening recognition of different people’s values and concerns. In addition, we find that as coastal developing communities face increasing social and environmental changes, the procedures for governing resources and thus the means to make fair decisions about distribution, is inextricably connected to recognitional aspects of justice, such as respect, that can confer or undermine legitimacy. The heterogeneity of justice criteria in our cases emphasizes the need to elicit and understand plural justice perceptions in different contexts

What matters to whom and why? Understanding the importance of coastal ecosystem services in developing coastal communities

Coastal ecosystems support the livelihoods and wellbeing of millions of people worldwide. However, the marine and terrestrial ecosystem services that coastal ecosystems provide are particularly vulnerable to global environmental change, as are the coastal communities who directly depend on them. To navigate these changes and ensure the wellbeing of coastal communities, policy-makers must know which coastal ecosystem services matter to whom, and why. Yet, in developing coastal settings, capturing people's perceptions of the importance of ecosystem services is challenging for several reasons. Firstly, coastal ecosystem services encompass both terrestrial and marine services across multiple categories (i.e. provisioning, supporting, and cultural) that are difficult to value together. Secondly, widely used monetary valuation techniques are often inappropriate because of culturally specific attributions of value, and the intangible nature of key cultural ecosystem services. Thirdly, people within communities may hold different ecosystem services values. In this paper, we examine how people ascribe and explain the importance of a range of marine and terrestrial ecosystem services in three coastal communities in Papua New Guinea. We use a mixed-methods approach that combines a non-monetary ranking and rating assessment of multiple ecosystem services, with a socio-economic survey (N = 139) and qualitative explanations of why ecosystem services matter. We find that people uniformly ascribe the most importance to marine and terrestrial provisioning services that directly support their livelihoods and material wellbeing. However, within communities, gender, wealth, and years of formal schooling do shape some differences in how people rate ecosystem services. In addition, although cultural ecosystem services were often rated lower, people emphasized that they ranked provisioning services highly, in part, because of their contribution to cultural values like bequest. People also expressed concern about extractive ecosystem services, like fuelwood, that were perceived to be destructive, and were rated low. We contend that comprehensive ecosystem services assessments that include narratives can capture the broad importance of a range of ecosystem services, alongside relational values and normative judgements. This exploratory approach is a useful step towards understanding the complexities of ecosystem services in developing coastal settings

An Ontology-Based Collaborative Interorganizational Knowledge Management Network

Web contents can be represented in a structural form by a finite list of vocabularies and their relationships using ontologies. The concept of ontology and its related mediation methods is capable of enhancing the collaboration among Knowledge Management (KM) approaches that only focus on managing organizational knowledge. Those KM approaches are developed in accordance with organizational KM strategies and business requirements without the concern of system interoperation. In this research, an ontology-based collaborative inter-organizational KM network is proposed to provide a platform for organizations to access and retrieve inter-organizational knowledge in a similar domain

An experimental look at trust, bargaining, and public goods in fishing communities

Pro-social behavior is crucial to the sustainable governance of common-pool resources such as fisheries. Here, we investigate how key socioeconomic characteristics influence fishers’ pro-social and bargaining behavior in three types of experimental economic games (public goods, trust, and trade) conducted in fishing associations in Chile. Our games revealed high levels of cooperation in the public goods game, a high degree of trust, and that sellers rather than buyers had more bargaining power, yet these results were strongly influenced by participants’ socioeconomic characteristics. Specifically, gender, having a secondary income source, age, and being the main income provider for the household all had a relationship to multiple game outcomes. Our results highlight that engagement in pro-social behaviors such as trust and cooperation can be influenced by people’s socioeconomic context