91 research outputs found
Free access to the documents and information of the EU institutions from the point of view of Czech legislation
Free access to information is considered to be one of the most important fundamental political rights of citizens. Free access to information has a long history originating in Sweden in the 18th century and has since then been incrementally constitutionalised in most of the democratic countries. It is worth studying the fact that legislation regulating this question in European Union legal systems, and in the Czech Republic as well, started much later — fifteen years ago at the beginning of the millennium. Even though the age of both the acts — EU (the Regulation of the European Parliament and the Council (EC) No. 1049/2001 of 30 May 2001 regarding public access to European Parliament, Council and Commission documents) and Czech (the Act (CZ) on Free Access to Information No. 106/1999) is the same, the legislation itself differs significantly and they both have legal shortcomings.Free access to information is considered to be one of the most important fundamental political rights of citizens. Free access to information has a long history originating in Sweden in the 18th century and has since then been incrementally constitutionalised in most of the democratic countries. It is worth studying the fact that legislation regulating this question in European Union legal systems, and in the Czech Republic as well, started much later — fifteen years ago at the beginning of the millennium. Even though the age of both the acts — EU (the Regulation of the European Parliament and the Council (EC) No. 1049/2001 of 30 May 2001 regarding public access to European Parliament, Council and Commission documents) and Czech (the Act (CZ) on Free Access to Information No. 106/1999) is the same, the legislation itself differs significantly and they both have legal shortcomings
How to Cut a Ball Without Separating: Improved Approximations for Length Bounded Cut
The Minimum Length Bounded Cut problem is a natural variant of Minimum Cut: given a graph, terminal nodes s,t and a parameter L, find a minimum cardinality set of nodes (other than s,t) whose removal ensures that the distance from s to t is greater than L. We focus on the approximability of the problem for bounded values of the parameter L.
The problem is solvable in polynomial time for L ? 4 and NP-hard for L ? 5. The best known algorithms have approximation factor ? (L-1)/2?. It is NP-hard to approximate the problem within a factor of 1.17175 and Unique Games hard to approximate it within ?(L), for any L ? 5. Moreover, for L = 5 the problem is 4/3-? Unique Games hard for any ? > 0.
Our first result matches the hardness for L = 5 with a 4/3-approximation algorithm for this case, improving over the previous 2-approximation. For 6-bounded cuts we give a 7/4-approximation, improving over the previous best 3-approximation. More generally, we achieve approximation ratios that always outperform the previous ? (L-1)/2? guarantee for any (fixed) value of L, while for large values of L, we achieve a significantly better ((11/25)L+O(1))-approximation.
All our algorithms apply in the weighted setting, in both directed and undirected graphs, as well as for edge-cuts, which easily reduce to the node-cut variant. Moreover, by rounding the natural linear programming relaxation, our algorithms also bound the corresponding bounded-length flow-cut gaps
Towards Duality of Multicommodity Multiroute Cuts and Flows: Multilevel Ball-Growing
An elementary h-route flow, for an integer h ≥ 1, is a set of h edge-disjoint paths between a source and a sink, each path carrying a unit of flow, and an h-route flow is a non-negative linear combination of elementary h-route flows. An h-route cut is a set of edges whose removal decreases the maximum h-route flow between a given source-sink pair (or between every source-sink pair in the multicommodity setting) to zero. The main result of this paper is an approximate duality theorem for multicommodity h-route cuts and flows, for h ≤ 3: The size of a minimum h-route cut is at least f/h and at most O(log 3 k·f) where f is the size of the maximum h-route flow and k is the number of commodities. The main step towards the proof of this duality is the design and analysis of a polynomial-time approximation algorithm for the minimum h-route cut problem for h = 3 that has an approximation ratio of O(log 3 k). Previously, polylogarithmic approximation was known only for h-route cuts for h ≤ 2. A key ingredient of our algorithm is a novel rounding technique that we call multilevel ball-growing. Though the proof of the duality relies on this algorithm, it is not a straightforward corollary of it as in the case of classical multicommodity flows and cuts. Similar results are shown also for the sparsest multiroute cut problem
Approximating reversal distance for strings with bounded number of duplicates
AbstractFor a string A=a1…an, a reversal ρ(i,j), 1⩽i⩽j⩽n, transforms the string A into a string A′=a1…ai-1ajaj-1…aiaj+1… an, that is, the reversal ρ(i,j) reverses the order of symbols in the substring ai…aj of A. In the case of signed strings, where each symbol is given a sign + or -, the reversal operation also flips the sign of each symbol in the reversed substring. Given two strings, A and B, signed or unsigned, sorting by reversals (SBR) is the problem of finding the minimum number of reversals that transform the string A into the string B.Traditionally, the problem was studied for permutations, that is, for strings in which every symbol appears exactly once. We consider a generalization of the problem, k-SBR, and allow each symbol to appear at most k times in each string, for some k⩾1. The main result of the paper is an O(k2)-approximation algorithm running in time O(n). For instances with 3<k⩽O(lognlog*n), this is the best known approximation algorithm for k-SBRand, moreover, it is faster than the previous best approximation algorithm
Extension Complexity, MSO Logic, and Treewidth
We consider the convex hull P_phi(G) of all satisfying assignments of a given MSO_2 formula phi on a given graph G. We show that there exists an extended formulation of the polytope P_phi(G) that can be described by f(|phi|,tau)*n inequalities, where n is the number of vertices in G, tau is the treewidth of G and f is a computable function depending only on phi and tau.
In other words, we prove that the extension complexity of P_phi(G) is linear in the size of the graph G, with a constant depending on the treewidth of G and the formula phi. This provides a very general yet very simple meta-theorem about the extension complexity of polytopes related to a wide class of problems and graphs
Zjednodušení legislativy
Někdy se mi zdá, vážení akademičtí čtenáři, že pro jednotlivé stromy nevidíme celý les. Myslím, že nová vláda (s bezpečnou parlamentní většinou v zádech) by si měla dát za prioritní úkol zpřehlednění klíčových právních předpisů, které dopadají na každého. Chtěl jsem původně napsat na každého občana, ale přesnější je na každou fyzickou osobu, protože mnohdy dopadají i na cizince
Méně je někdy více
Jako učitel správního práva a správní vědy jsem si povšiml, že je stále častějším fenoménem, že si správní úřad (dělají to i soukromé firmy, ale to není předmětem tohoto článku) objedná externí společnost, která umí efektivně sledovat, co zaměstnanci úřadu dělají v pracovní době na počítači. Tedy na pracovním počítači
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