Inventories in the crisis.

At the end of 2008, a massive and worldwide drawdown of inventories contributed to the strong contraction in international trade and activity. This movement was no doubt exacerbated by the financial constraints on companies and the transmission of the shock along globalised production chains. Conversely, from mid-2009 onwards, destocking slowed, contributing to a V-shaped recovery.inventory cycle, just-in-time, great recession, bullwhip effect, financial constraints.

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

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

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 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

¿Cambiar la vida o cambiar el hombre?

Documento escrito en 1935 que sitúa los axiomas de Marx y Engels sobre el plano de la historia, comparando la dictadura de Stalin con los regímenes fascistas. Propone la continuidad de la actitud comunista, pero con la voluntad de cambiar el mundo, de transformar la historia con movimientos legítimos y creadores. F.I autor hace una confrontación entre las propuestas de los cristianos (Evangelio) y la doctrina marxista