The Complexity of Change

Many combinatorial problems can be formulated as "Can I transform configuration 1 into configuration 2, if certain transformations only are allowed?". An example of such a question is: given two k-colourings of a graph, can I transform the first k-colouring into the second one, by recolouring one vertex at a time, and always maintaining a proper k-colouring? Another example is: given two solutions of a SAT-instance, can I transform the first solution into the second one, by changing the truth value one variable at a time, and always maintaining a solution of the SAT-instance? Other examples can be found in many classical puzzles, such as the 15-Puzzle and Rubik's Cube. In this survey we shall give an overview of some older and more recent work on this type of problem. The emphasis will be on the computational complexity of the problems: how hard is it to decide if a certain transformation is possible or not?Comment: 28 pages, 6 figure

Algorithmic aspects of a chip-firing game

Algorithmic aspects of a chip-firing game on a graph introduced by Biggs are studied. This variant of the chip-firing game, called the dollar game, has the properties that every starting configuration leads to a so-called critical configuration. The set of critical configurations has many interesting properties. In this paper it is proved that the number of steps needed to reach a critical configuration is polynomial in the number of edges of the graph and the number of chips in the starting configuration, but not necessarily in the size of the input. An alternative algorithm is also described and analysed

Loan maturity aggregation in interbank lending networks obscures mesoscale structure and economic functions

Since the 2007-2009 financial crisis, substantial academic effort has been dedicated to improving our understanding of interbank lending networks (ILNs). Because of data limitations or by choice, the literature largely lacks multiple loan maturities. We employ a complete interbank loan contract dataset to investigate whether maturity details are informative of the network structure. Applying the layered stochastic block model of Peixoto (2015) and other tools from network science on a time series of bilateral loans with multiple maturity layers in the Russian ILN, we find that collapsing all such layers consistently obscures mesoscale structure. The optimal maturity granularity lies between completely collapsing and completely separating the maturity layers and depends on the development phase of the interbank market, with a more developed market requiring more layers for optimal description. Closer inspection of the inferred maturity bins associated with the optimal maturity granularity reveals specific economic functions, from liquidity intermediation to financing. Collapsing a network with multiple underlying maturity layers or extracting one such layer, common in economic research, is therefore not only an incomplete representation of the ILN's mesoscale structure, but also conceals existing economic functions. This holds important insights and opportunities for theoretical and empirical studies on interbank market functioning, contagion, stability, and on the desirable level of regulatory data disclosure

Transversals of subtree hypergraphs and the source location problem in hypergraphs

A hypergraph $H=(V,E)$ is a subtree hypergraph if there is a tree~$T$ on~$V$ such that each hyperedge of~$E$ induces a subtree of~$T$. Since the number of edges of a subtree hypergraph can be exponential in $n=|V|$, one can not always expect to be able to find a minimum size transversal in time polynomial in~$n$. In this paper, we show that if it is possible to decide if a set of vertices $W\subseteq V$ is a transversal in time~$S(n)$ (\,where $n=|V|$\,), then it is possible to find a minimum size transversal in~$O(n^3\,S(n))$. This result provides a polynomial algorithm for the Source Location Problem\,: a set of $(k,l)$-sources for a digraph $D=(V,A)$ is a subset~$S$ of~$V$ such that for any $v\in V$ there are~$k$ arc-disjoint paths that each join a vertex of~$S$ to~$v$ and~$l$ arc-disjoint paths that each join~$v$ to~$S$. The Source Location Problem is to find a minimum size set of $(k,l)$-sources. We show that this is a case of finding a transversal of a subtree hypergraph, and that in this case~$S(n)$ is polynomial

Educating the Next Generation of Global Information Managers

In this paper we examine the only T-Shaped,Atlantis-supported global dual degree program inInformation Management, the International Bachelor’sin Information Management. Atlantis promotes astudent-centered, transatlantic dimension to a highereducation and training in a wide range of academic andprofessional disciplines and funds collaborative efforts todevelop programs of study leading to joint or dualundergraduate or graduate degrees. The Atlantisprogram, jointly administered and funded by the U.S.Department of Education’s Fund for the Improvement ofPostsecondary Education and the European Union’sEducation, Audiovisual and Culture Executive Agency,supports the level of international educational immersionrecommended here

Transformation of the Software Components and Web Services Market

The Service Oriented Computing paradigm, with as its main manifestation web-service technology, holds high promises, but exploits its full potential only when third-party web-services are traded in a service market to enable effective development of net-enhanced organizations and business networks. After the introduction of software source code libraries and the rise of Software Component Markets (SCMs) since 1999, Web Service Markets (WSM) represent the third wave in the trade of reusable software components. However, very little is known about the current status, structure and trends within the WSM. We present a longitudinal study of the structure of the SCM in 1999, 2000, and 2006 and a study of the WSM in 2006. The SCM has grown into a large, polluted, and un-transparent market of around 30,000 software components, offered by 28 producers, 28 catalogues, and 8 intermediaries. Our study shows that the WSM is emerging and in the early stage of development in 2006. SCM and WSM still have a long way to become transparent and effective mechanisms for organizations to obtain powerful, re-usable, and interoperable components for business networking