492 lines
15 KiB
TeX
492 lines
15 KiB
TeX
% $Header$
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% use lualatex for compilation
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\documentclass[aspectratio=169,navbar=false]{beamer}
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% This file is a solution template for:
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% - Talk at a conference/colloquium.
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% - Talk length is about 20min.
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% - Style is ornate.
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% Copyright 2004 by Till Tantau <tantau@users.sourceforge.net>.
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%
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% In principle, this file can be redistributed and/or modified under
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% the terms of the GNU Public License, version 2.
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%
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% However, this file is supposed to be a template to be modified
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% for your own needs. For this reason, if you use this file as a
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% template and not specifically distribute it as part of a another
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% package/program, I grant the extra permission to freely copy and
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% modify this file as you see fit and even to delete this copyright
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% notice.
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\mode<presentation>
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{
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\usetheme[cd2018,noddc,darktitlepage]{tud}
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\usecolortheme{tud}
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% or ...
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%\setbeamercovered{transparent}
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% or whatever (possibly just delete it)
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}
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% notes on 2nd screen:
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\usepackage{pgfpages}
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\setbeameroption{show notes on second screen}
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\usepackage[british]{babel}
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% or whatever
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\usepackage[backend=biber, sorting=none]{biblatex}
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\usepackage{ccicons}
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\usepackage{wrapfig}
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\usepackage{ifluatex}
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\ifluatex
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\usepackage{fontspec}
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%\setmainfont{TeX Gyre Pagella}
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%\RequirePackage{unicode-math}
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%\setmathfont{XITS Math}
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%\setmainfont{Open Sans}
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%\setsansfont{Open Sans}
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%\setmathfont[range={it}]{Open Sans:style=Italic}
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%\setmathfont[range={it}]{Open Sans}
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\else
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\usepackage[T1]{fontenc}
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\usepackage[utf8]{inputenc}
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% Or whatever. Note that the encoding and the font should match. If T1
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% does not look nice, try deleting the line with the fontenc.
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\fi
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\title[Decentralised Hashtag Federation] % (optional, use only with long paper titles)
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{Decentralised Hashtag Search and Subscription
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for Federated Social Networks}
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\author
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{Trolli Schmittlauch}
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% - Give the names in the same order as the appear in the paper.
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% - Use the \inst{?} command only if the authors have different
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% affiliation.
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\institute[] % (optional, but mostly needed)
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{
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Department of Computer Science\\
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Technical University Dresden
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}
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\date[APConf 2019] % (optional, should be abbreviation of conference name)
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{ActivityPubConf 2019}
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\datecity{Prague}
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% - Either use conference name or its abbreviation.
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% - Not really informative to the audience, more for people (including
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% yourself) who are reading the slides online
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%\subject{Privacy}
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% This is only inserted into the PDF information catalog. Can be left
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% out.
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% If you have a file called "university-logo-filename.xxx", where xxx
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% is a graphic format that can be processed by latex or pdflatex,
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% resp., then you can add a logo as follows:
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% \pgfdeclareimage[height=0.5cm]{university-logo}{university-logo-filename}
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% \logo{\pgfuseimage{university-logo}}
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% Delete this, if you do not want the table of contents to pop up at
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% the beginning of each subsection:
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%\AtBeginSubsection[]
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%{
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% \begin{frame}<beamer>{Outline}
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% \tableofcontents[currentsection,currentsubsection]
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% \end{frame}
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%}
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% If you wish to uncover everything in a step-wise fashion, uncomment
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% the following command:
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%\beamerdefaultoverlayspecification{<+->}
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\begin{document}
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\maketitle
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\note{introduce myself:\\
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known as schmittlauch on the Internet\\
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student of Computer Science @ TU Dresden\\
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interest in federated systems and unusual social networks\\
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presenting my work on a study paper from this year}
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\begin{frame}{Outline}
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\tableofcontents
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% You might wish to add the option [pausesections]
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\end{frame}
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% Structuring a talk is a difficult task and the following structure
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% may not be suitable. Here are some rules that apply for this
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% solution:
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% - Exactly two or three sections (other than the summary).
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% - At *most* three subsections per section.
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% - Talk about 30s to 2min per frame. So there should be between about
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% 15 and 30 frames, all told.
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% - A conference audience is likely to know very little of what you
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% are going to talk about. So *simplify*!
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% - In a 20min talk, getting the main ideas across is hard
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% enough. Leave out details, even if it means being less precise than
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% you think necessary.
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% - If you omit details that are vital to the proof/implementation,
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% just say so once. Everybody will be happy with that.
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\section{Motivation}
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\begin{frame}{Welcome to ActivityPubConf!}{Motivation}
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\only<1>{
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\includegraphics[width=\textwidth]{figures/toot_nohashtags.png}
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\note{Who has been posting about this Conference?}
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}
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\only<2>{
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\includegraphics[width=\textwidth]{figures/toot_hashtags.png}
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\note{And who used \#ActivityPubConf?}
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}
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\end{frame}
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\subsection{Importance of \#Hashtags}
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\begin{frame}{Importance of \#Hashtags}{}
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Hashtags are used for marking posts about certain topics or events:
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\note{mark topics of posts, make them discoverable by content. No full text search in fediverse}
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\begin{columns}
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\begin{column}{0.47\textwidth}
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\begin{itemize}
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\item<1-> \textbf{events}: \#ActivityPubConf, \#CCCamp19
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\item<2-> \textbf{political topics}: \#SaveTheInternet
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\item<3-> \textbf{general topics}: \#mastoadmin, \#Tusky
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\item<4-> \textbf{ongoing demonstrations}: \#GeziPark, \#WomensMarch
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\item<5-> \textbf{social movements}: \#MeToo
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\end{itemize}
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\end{column}
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\begin{column}{0.5\textwidth}
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\begin{overlayarea}{\textwidth}{0.6\paperheight}
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\center
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\only<1>{
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\includegraphics[width=\textwidth]{figures/APConfLogo.png}
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}
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\only<2>{
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\includegraphics[height=0.58\paperheight]{figures/hashtag_savetheinternet.jpg}\\
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\tiny{\href{https://www.flickr.com/photos/8183946@N05/14733648892}{"Obama in the Backseat: Rally to Save the Internet"} by \href{https://www.flickr.com/photos/8183946@N05}{Free Press Pics} is licensed under \href{https://creativecommons.org/licenses/by-sa/2.0/?ref=ccsearch&atype=rich}{CC BY-SA 2.0} \ccbysa}
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}
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\only<3>{
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\includegraphics[height=0.6\paperheight]{figures/Elephant_Friend_(Greeting).png}
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}
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\only<4>{
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\includegraphics[width=\textwidth]{figures/hashtag_gezipark.jpg}
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}
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\only<5>{
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\includegraphics[height=0.6\paperheight]{figures/hashtag_metoo.jpg}\\
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\tiny{\href{https://www.flickr.com/photos/50612692@N04/28039368079}{"IMG\_4263"} by \href{https://www.flickr.com/photos/50612692@N04}{GGAADD} is licensed under \href{https://creativecommons.org/licenses/by-sa/2.0/?ref=ccsearch&atype=rich}{CC BY-SA 2.0} \ccbysa}
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}
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\end{overlayarea}
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\end{column}
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\end{columns}
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\end{frame}
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\subsection{State of Hashtags in the Fediverse}
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\begin{frame}{State of Hashtags on the Fediverse}{}
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{\center \Large Hashtags are used in the fediverse}
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\pause
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\vspace{2em}
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{\large But do they behave as expected?}
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\end{frame}
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\begin{frame}
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\begin{columns}
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\begin{column}{0.5\textwidth}
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\begin{figure}
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\includegraphics[height=0.65\paperheight]{figures/{activitypubconf_toot.matereal.eu}.png}
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\caption{\#activitypubconf on the single-user instance \textit{toot.matereal.eu}}
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\end{figure}
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\end{column}
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\begin{column}{0.5\textwidth}
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\begin{figure}
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\includegraphics[height=0.65\paperheight]{figures/{activitypubconf_mastodon.social}.png}
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\caption{\#activitypubconf on the large instance \textit{mastodon.social}}
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\end{figure}
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\end{column}
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\end{columns}
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\end{frame}
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\begin{frame}{State of Hashtags on the Fediverse}{Fragmentation}
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\begin{itemize}
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\item fragmented view on hashtag posts depending on user's instance
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\item hashtag search only on locally known posts
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\item Result: incentive to cluster on large nodes \(\Leftarrow\) centralisation
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\end{itemize}
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\end{frame}
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\begin{frame}{Reason}{Push-Federation}
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\begin{columns}
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\begin{column}{0.55\textwidth}
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\includegraphics[height=0.6\paperheight]{figures/push_federation.pdf}
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\end{column}
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\begin{column}{0.45\textwidth}
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\begin{itemize}
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\only<1>{\item subscription to \texttt{@alice@cyber.space} by contacting instance \texttt{cyber.space}}
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\only<2>{\item all future posts by alice are delivered to instances of subscribers, but \textit{not} instances without any subscriber}
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\only<3>{\item other ways for posts to reach an instance:\\ boosts, thread resolution}
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\end{itemize}
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\end{column}
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\end{columns}
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\end{frame}
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\begin{frame}{Current Solutions}
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\begin{itemize}
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\item Mastodon PubRelay or Pleroma lite-pub relay:
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\begin{itemize}
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\item centralised actor relaying all incoming posts
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\item single point of failure, which relay to choose?
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\item relaying all incoming posts \(\Rightarrow\) huge load on small instances
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\item only access to posts sent after initial subscribtion
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\end{itemize}
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\item Diaspora* SocialRelay
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\begin{itemize}
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\item similar, but allows subscribing to certain tags only
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\end{itemize}
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\end{itemize}
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\end{frame}
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\section{System Architecture}
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\begin{frame}{System Architecture}{Goals}
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\begin{itemize}
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\item \textbf{relay \& subscribe}: instances can subscribe to all public posts of a hashtag
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\item \textbf{store \& query}: instances can retrieve 1 year of history for a hashtag without subscription
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\item fully decentralised, no single point of authority for all tags
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\end{itemize}
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\end{frame}
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\begin{frame}{System Architecture}{adding a DHT backend to the fediverse}
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core idea: distribute responsibility for tags among instances using a \textbf{D}istributed \textbf{H}ash \textbf{T}able, \note{distribute responsibility for posts of a hashtag = relaying \& storage}
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based on Chord
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\note[item]{DHT: structured P2P networks providing efficient (log N) key-value storage and lookup}
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\note[item]{self-organising, no central authority}
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\end{frame}
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\begin{frame}{System Architecture}{adding a DHT backend to the fediverse}
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\begin{columns}
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\begin{column}{0.4\textwidth}
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\begin{itemize}
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\item calculate hash value of keys and node IDs
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\item place these hashes onto the same circular name space
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\item each node keeps routing table of \(\log \#number\_nodes\) entries\note[item]{joining and leaving covered in paper}
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\end{itemize}
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\end{column}
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\begin{column}{0.6\textwidth}
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\includegraphics[height=0.62\paperheight]{figures/finger_table_routing_1.pdf}
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\end{column}
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\end{columns}
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\end{frame}
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\begin{frame}{System Architecture}{adding a DHT backend to the fediverse}
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\begin{columns}
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\begin{column}{0.55\textwidth}
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\begin{itemize}
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\item next nodeID \(\geq\) \texttt{hash(hashtag)} (mod keyspace size) is responsible for handling posts containing \texttt{hashtag}
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\item DHT used for iterative lookup of responsible relay/ storage node
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\end{itemize}
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\end{column}
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\begin{column}{0.45\textwidth}
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\includegraphics[height=0.62\paperheight]{figures/finger_table_routing_2.pdf}
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\end{column}
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\end{columns}
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\end{frame}
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\begin{frame}{Publishing, Relaying and Storage}{lifecycle of posts}
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\begin{enumerate}
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\item publishing instance looks up responsible relay instance on DHT for each included hashtag
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\item publishing instance sends post to responsible relay instance
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\item relay instance looks up responsible storage node on DHT
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\item relay instance verifies incoming post's signature, then relays post URI (ID) to all subscribers + storage node\note[item]{only post ID relayed, but not full post content. Reasons: LDSignatures not supported everywhere, deniability \& revocation}
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\item subscribing instances can now retrieve the full authenticated post from received post URI
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\end{enumerate}
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\end{frame}
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\begin{frame}{Publishing, Relaying and Storage}
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\begin{itemize}
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\item separate DHTs for relay and storage instances
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\item all actions after DHT lookup supposed to be done using ActivityPub via HTTPS
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\item subscription to hashtags/ querying posts is done at the responsible instance
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\end{itemize}
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\end{frame}
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\begin{frame}
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\note{so far so easy. But load distribution issues}
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\begin{itemize}
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\item node ID determines set of hashtags handled by instance
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\item problem: for security reasons, node \textbf{must not} choose their IDs freely
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\item Can instances be overloaded by their assigned hashtag posts?
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\end{itemize}
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\end{frame}
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\begin{frame}{Distribution of Posts per Tag}
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\includegraphics[width=0.49\textwidth]{statistics/twitter_hashtags_total.png}
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~
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\includegraphics[width=0.49\textwidth]{statistics/geraspora_hashtags_total.png}
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\note{analysis of a 1 month dump of Twitter, Geraspora (Diaspora) and Friendica posts\\
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Twitter: 70\% of posts used just once\\
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note the logarithmic axis!}
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distribution of posts per hashtag follows a steep power law
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\note{So what if a small node gets several large hashtags? => need for load balancing}
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\end{frame}
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\begin{frame}{Load Balancing}{of hashtags between nodes}
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\begin{itemize}
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\item \textit{k-choices} algorithm by Ledlie and Seltzer
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\item each node can choose from \(\kappa\) possible IDs
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\item nodes have a \textbf{capacity} and choose set of active IDs according to lowest mismatch of own and neighbour node capacity
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\item querying load of potential IDs before joining, periodic re-balancing
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\item independent load balancing of relay and storage nodes due to independent DHTs
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\end{itemize}
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% for Kolloquium, add simulation result
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\end{frame}
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\begin{frame}{Redundancy}
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\begin{columns}
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\begin{column}{0.55\textwidth}
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\begin{itemize}
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\item store redundant copies of hashtag data at equal distances on Chord ring\note{resilience against node failure, allows data validation through cross-checking}
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\item default redundancy: \(2^2 = 4\), scalable in powers of 2
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\item \textbf{relay nodes}: hot standby nodes take over in overload situations (load spikes)
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\item \textbf{storage nodes}: overloaded nodes can split stored posts by content hash and double redundancy set
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\end{itemize}
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\end{column}
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\begin{column}{0.45\textwidth}
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\includegraphics[width=\textwidth]{figures/redundancy_ring.pdf}
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\end{column}
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\end{columns}
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\end{frame}
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why even still use classic push federation?
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\section{Discussion}
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\begin{frame}{Discussion}{I need YOUR feedback}
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I want feedback from all of you, no matter whether it's from a \textit{\LARGE technical} or from a \textit{\LARGE social perspective}.
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\end{frame}
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\subsection{Social Considerations}
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\subsection{Technical Considerations}
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CloudFlare
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load and capacity factor
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performance: batching, exponential back-off, no relayable sigs
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security: node ID derivation scheme
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\section{Summary}
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\begin{frame}{Summary}
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% Keep the summary *very short*.
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\begin{itemize}
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\item
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things can be \alert{highlighted}.
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\end{itemize}
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% The following outlook is optional.
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\vskip0pt plus.5fill
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\begin{itemize}
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\item
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Outlook
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\end{itemize}
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\end{frame}
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% All of the following is optional and typically not needed.
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\appendix
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\section<presentation>*{\appendixname}
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\subsection<presentation>*{For Further Reading}
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\begin{frame}[allowframebreaks]
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\frametitle{References}
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%\bibliography{literature}
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\end{frame}
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\begin{frame}{Complete Paper}
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\center
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\includegraphics[height=0.45\paperheight]{figures/qr_paper.png}\\
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\url{https://git.orlives.de/schmittlauch/paper_hashtag_federation/src/branch/master/paper_hashtag_federation.pdf}
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\end{frame}
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\begin{frame}
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\center\huge{Thank you for your attention!}
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%\includegraphics[height=0.5\textheight]{figures/nomnompingu.png}\tiny\footnote{CC-BY-SA 3.0 by Elektroll}
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\end{frame}
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\end{document}
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