The Value of Sponsored Ads for XML Documents

We study how sponsored ads which are classically inserted in Web pages could also be inserted in XML documents such as Ebooks. Advertisers set prices for words and DTDs, and a Vickrey mechanism would select an ad for some price. The approximate distance between a document and any DTD, which is easy to compute, allows to associate a value to a new document in such a market, as a combination of the price and the distance. We describe a simple auction for one ad and its generalization to several ads

Approximate Analytics for The Cloud

We model the cloud as a network of servers holding large XML trees, where the communication costs between servers are high and the local computations costs are low. We propose a general method, StatsReduce, which combines some statistical information of the data on each server and construct a global statistics for the combination of the trees. We show how to use this global statistics to approximately answer Analytics queries on the global data, in the case of a composition of trees. The value of new services on the cloud is dependent on the efficient estimation of Analytics queries with methods such as StatsReduce

Streaming Property Testing of Visibly Pushdown Languages

In the context of language recognition, we demonstrate the superiority of streaming property testers against streaming algorithms and property testers, when they are not combined. Initiated by Feigenbaum et al., a streaming property tester is a streaming algorithm recognizing a language under the property testing approximation: it must distinguish inputs of the language from those that are $\varepsilon$-far from it, while using the smallest possible memory (rather than limiting its number of input queries). Our main result is a streaming $\varepsilon$-property tester for visibly pushdown languages (VPL) with one-sided error using memory space $\mathrm{poly}((\log n) / \varepsilon)$. This constructions relies on a (non-streaming) property tester for weighted regular languages based on a previous tester by Alon et al. We provide a simple application of this tester for streaming testing special cases of instances of VPL that are already hard for both streaming algorithms and property testers. Our main algorithm is a combination of an original simulation of visibly pushdown automata using a stack with small height but possible items of linear size. In a second step, those items are replaced by small sketches. Those sketches relies on a notion of suffix-sampling we introduce. This sampling is the key idea connecting our streaming tester algorithm to property testers.Comment: 23 pages. Major modifications in the presentatio

Streaming Property Testing of Visibly Pushdown Languages

In the context of formal language recognition, we demonstrate the superiority of streaming property testers against streaming algorithms and property testers, when they are not combined. Initiated by Feigenbaum et al., a streaming property tester is a streaming algorithm recognizing a language under the property testing approximation: it must distinguish inputs of the language from those that are eps-far from it, while using the smallest possible memory (rather than limiting its number of input queries). Our main result is a streaming eps-property tester for visibly pushdown languages (V_{PL}) with memory space poly(log n /epsilon). Our construction is done in three steps. First, we simulate a visibly pushdown automaton in one pass using a stack of small height but whose items can be of linear size. In a second step, those items are replaced by small sketches. Those sketches rely on a notion of suffix-sampling we introduce. This sampling is the key idea for taking benefit of both streaming algorithms and property testers in the third step. Indeed, the last step relies on a (non-streaming) property tester for weighted regular languages based on a previous tester by Alon et al. This tester can directly be used for streaming testing special cases of instances of V_{PL} that are already hard for both streaming algorithms and property testers. We then use it to decide the correctness of completed items, given their sketches, before removing them from the stack

Testing Membership for Timed Automata

Given a timed automata which admits thick components and a timed word $x$, we present a tester which decides if $x$ is in the language of the automaton or if $x$ is $\epsilon$-far from the language, using finitely many samples taken from the weighted time distribution $\mu$ associated with an input $x$. We introduce a distance between timed words, the {\em timed edit distance}, which generalizes the classical edit distance. A timed word $x$ is $\epsilon$-far from a timed language if its relative distance to the language is greater than $\epsilon$.Comment: 26 page

Complexité des dynamiques de jeux

La th eorie de la complexit e permet de classi er les problemes en fonction de leur di cult e. Le cadre classique dans lequel elle s applique est celui d un algorithme centralis e qui dispose de toutes les informations. Avec l essor des r eseaux et des architectures d ecentralis ees, l algo- rithmique distribu ee a et e etudi ee. Dans un grand nombre de problemes, en optimisation et en economie, les d ecisions et les calculs sont e ectu es par des agents ind ependants qui suivent des objectifs di erents dont la r ealisation d epend des d ecisions des autres agents. La th eorie des jeux est un cadre naturel pour analyser les solutions de tels problemes. Elle propose des concepts de stabilit e, le plus classique etant l equilibre de Nash.Une maniere naturelle de calculer de telles solutions est de faire r eagir les agents ; si un agent voit quelles sont les d ecisions des autres joueurs ou plus g en eralement un etat du jeu , il peut d ecider de changer sa d ecision pour atteindre son objectif faisant ainsi evoluer l etat du jeu. On dit que ces algorithmes sont des dynamiques .On sait que certaines dynamiques convergent vers un concept de solution. On s int eresse a la vitesse de convergence des dynamiques. Certains concepts de solutions sont m eme complets pour certaines classes de complexit e ce qui rend peu vraisemblable l existence de dynamiques simples qui convergent rapidement vers ces solutions. On a utilis e alors trois approches pour obtenir une convergence rapide : am eliorer la dynamique (en utilisant par exemple des bits al eatoires), restreindre la structure du probleme, et rechercher une solution approch ee.Sur les jeux de congestion, on a etendu les r esultats de convergence rapide vers un equilibre de Nash approch e aux jeux n egatifs. Cependant, on a montr e que sur les jeux sans contrainte de signe, calculer un equilibre de Nash approch e est PLS-complet. Sur les jeux d appariement, on a etudi e la vitesse de dynamiques concurrentes lorsque les joueurs ont une information partielle param etr ee par un r eseau social. En particulier, on a am elior e des dynamiques naturelles a n qu elles atteignent un equilibre enO(log(n)) tours (avec n le nombre de joueurs).Complexity theory allows to classify problems by their algorithmic hardness. The classical framework in which it applies is the one of a centralized algorithm that knows every informa- tion. With the development of networks and decentralized architectures, distributed dynamics was studied. In many problems, in optimization or economy, actions and computations are made by independant agents that don t share the same objective whose realization depends on the actions of other agents. Game theory is a natural framework to study solutions of this kind of problem. It provides solution concepts such as the Nash equilibrium.A natural way to compute these solutions is to make the agents react ; if an agent sees the actions of the other player, or more generally the state of the game, he can decide to change his decision to reach his objective and updates the state of the game. We call dynamics this kind of algorithms.We know some dynamics converges to a stable solution. We are interested by the speed of convergence of these dynamics. Some solution concepts are even complete for some complexity classes which make unrealistic the existence of fast converging dynamics. We used three ways to obtain a fast convergence : improving dynamics (using random bits), nding simple subcases, and nding an approximate solution.We extent fast convergence results to an approximate Nash equilibria in negative congestion games. However, we proved that nding an approximate Nash equilibrium in a congestion games without sign restriction is PLS-complete. On matching game, we studied the speed of concurrent dynamics when players have partial information that depends on a social network. Especially, we improved natural dynamics for them to reach an equilibrium inO(log(n)) rounds (with n is the number of players).PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

Kiri Karl Morgensternile, Paris

http://tartu.ester.ee/record=b1826371~S1*es