51,095 research outputs found
Making Name-Based Content Routing More Efficient than Link-State Routing
The Diffusive Name-based Routing Protocol (DNRP) is introduced for efficient
name-based routing in information-centric networks (ICN). DNRP establishes and
maintains multiple loop-free routes to the nearest instances of a name prefix
using only distance information. DNRP eliminates the need for periodic updates,
maintaining topology information, storing complete paths to content replicas,
or knowing about all the sites storing replicas of named content. DNRP is
suitable for large ICNs with large numbers of prefixes stored at multiple
sites. It is shown that DNRP provides loop-free routes to content independently
of the state of the topology and that it converges within a finite time to
correct routes to name prefixes after arbitrary changes in the network topology
or the placement of prefix instances. The result of simulation experiments
illustrates that DNRP is more efficient than link-state routing approaches
Revisiting Date and Party Hubs: Novel Approaches to Role Assignment in Protein Interaction Networks
The idea of 'date' and 'party' hubs has been influential in the study of
protein-protein interaction networks. Date hubs display low co-expression with
their partners, whilst party hubs have high co-expression. It was proposed that
party hubs are local coordinators whereas date hubs are global connectors. Here
we show that the reported importance of date hubs to network connectivity can
in fact be attributed to a tiny subset of them. Crucially, these few, extremely
central, hubs do not display particularly low expression correlation,
undermining the idea of a link between this quantity and hub function. The
date/party distinction was originally motivated by an approximately bimodal
distribution of hub co-expression; we show that this feature is not always
robust to methodological changes. Additionally, topological properties of hubs
do not in general correlate with co-expression. Thus, we suggest that a
date/party dichotomy is not meaningful and it might be more useful to conceive
of roles for protein-protein interactions rather than individual proteins. We
find significant correlations between interaction centrality and the functional
similarity of the interacting proteins.Comment: 27 pages, 5 main figures, 4 supplementary figure
Matching Dynamics with Constraints
We study uncoordinated matching markets with additional local constraints
that capture, e.g., restricted information, visibility, or externalities in
markets. Each agent is a node in a fixed matching network and strives to be
matched to another agent. Each agent has a complete preference list over all
other agents it can be matched with. However, depending on the constraints and
the current state of the game, not all possible partners are available for
matching at all times. For correlated preferences, we propose and study a
general class of hedonic coalition formation games that we call coalition
formation games with constraints. This class includes and extends many recently
studied variants of stable matching, such as locally stable matching, socially
stable matching, or friendship matching. Perhaps surprisingly, we show that all
these variants are encompassed in a class of "consistent" instances that always
allow a polynomial improvement sequence to a stable state. In addition, we show
that for consistent instances there always exists a polynomial sequence to
every reachable state. Our characterization is tight in the sense that we
provide exponential lower bounds when each of the requirements for consistency
is violated. We also analyze matching with uncorrelated preferences, where we
obtain a larger variety of results. While socially stable matching always
allows a polynomial sequence to a stable state, for other classes different
additional assumptions are sufficient to guarantee the same results. For the
problem of reaching a given stable state, we show NP-hardness in almost all
considered classes of matching games.Comment: Conference Version in WINE 201
Higher chordality: From graphs to complexes
We generalize the fundamental graph-theoretic notion of chordality for higher
dimensional simplicial complexes by putting it into a proper context within
homology theory. We generalize some of the classical results of graph
chordality to this generality, including the fundamental relation to the Leray
property and chordality theorems of Dirac.Comment: 13 pages, revised; to appear in Proc. AM
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