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+#+COLUMNS: %40ITEM %10BEAMER_env(Env) %9BEAMER_envargs(Env Args) %10BEAMER_act(Act) %4BEAMER_col(Col) %10BEAMER_extra(Extra) %8BEAMER_opt(Opt)
+#+TITLE: Software Heritage
+#+SUBTITLE: Analyzing the Global Graph of Public Software Development
+#+BEAMER_HEADER: \date[2021-05-19, ACES]{19 May 2021\\Team ACES --- Télécom Paris\\ (online)\\[-2ex]}
+#+AUTHOR: Stefano Zacchiroli
+#+DATE: 19 May 2021
+#+EMAIL: zack@upsilon.cc
+
+#+INCLUDE: "../../common/modules/prelude-toc.org" :minlevel 1
+#+INCLUDE: "../../common/modules/169.org"
+#+BEAMER_HEADER: \institute[UParis \& Inria]{Université de Paris \& Inria --- {\tt zack@upsilon.cc, @zacchiro}}
+#+BEAMER_HEADER: \author{Stefano Zacchiroli}
+
+# Syntax highlighting setup
+#+LATEX_HEADER_EXTRA: \usepackage{minted}
+#+LaTeX_HEADER_EXTRA: \usemintedstyle{tango}
+#+LaTeX_HEADER_EXTRA: \newminted{sql}{fontsize=\scriptsize}
+#+name: setup-minted
+#+begin_src emacs-lisp :exports results :results silent
+   (setq org-latex-listings 'minted)
+   (setq org-latex-minted-options
+         '(("fontsize" "\\scriptsize")
+           ("linenos" "")))
+   (setq org-latex-to-pdf-process
+         '("pdflatex -shell-escape -interaction nonstopmode -output-directory %o %f"
+           "pdflatex -shell-escape -interaction nonstopmode -output-directory %o %f"
+           "pdflatex -shell-escape -interaction nonstopmode -output-directory %o %f"))
+#+end_src
+# End syntax highlighting setup
+
+* About me                                                  :B_ignoreheading:
+  :PROPERTIES:
+  :BEAMER_env: ignoreheading
+  :END:
+  #+INCLUDE: "this/zack.org" :minlevel 2
+* Software Heritage
+#+INCLUDE: "../../common/modules/swh-goals-oneslide-vertical.org::#goals" :minlevel 2
+** An international, non profit initiative
+  :PROPERTIES:
+  :CUSTOM_ID: support
+  :END:
+*** Sharing the vision                                              :B_block:
+  :PROPERTIES:
+  :CUSTOM_ID: endorsement
+  :BEAMER_COL: .5
+  :BEAMER_env: block
+  :END:
+   #+LATEX: \begin{center}{\includegraphics[width=\extblockscale{.4\linewidth}]{unesco_logo_en_285}}\end{center}
+   #+LATEX: \vspace{-0.8cm}
+   #+LATEX: \begin{center}\vskip 1em \includegraphics[width=\extblockscale{1.4\linewidth}]{support.pdf}\end{center}
+   #+latex:\mbox{}~~~~~~~\tiny\url{www.softwareheritage.org/support/testimonials}
+*** Donors, members, sponsors                                       :B_block:
+    :PROPERTIES:
+    :CUSTOM_ID: sponsors
+    :BEAMER_COL: .5
+    :BEAMER_env: block
+    :END:
+   #+LATEX: \begin{center}\includegraphics[width=\extblockscale{.4\linewidth}]{inria-logo-new}\end{center}
+   #+LATEX: \begin{center}
+   #+LATEX: \colorbox{white}{\includegraphics[width=\extblockscale{1.4\linewidth}]{sponsors.pdf}}
+   #+latex:\mbox{}~~~~~~~\tiny\url{www.softwareheritage.org/support/sponsors}
+   #+LATEX: \end{center}
+** Status                                                   :B_ignoreheading:
+   :PROPERTIES:
+   :BEAMER_env: ignoreheading
+   :END:
+#+INCLUDE: "../../common/modules/status-extended.org::#archivinggoals" :minlevel 2
+#+INCLUDE: "../../common/modules/status-extended.org::#architecture" :minlevel 2 :only-contents t
+#+INCLUDE: "../../common/modules/status-extended.org::#merkletree" :minlevel 2
+#+INCLUDE: "../../common/modules/data-model.org::#merklestruct" :minlevel 2
+#+INCLUDE: "../../common/modules/status-extended.org::#dagdetailsmall" :minlevel 2 :only-contents t
+#+INCLUDE: "../../common/modules/status-extended.org::#archive" :minlevel 2
+* Querying the archive
+** Use cases --- product needs
+   e.g., for https://archive.softwareheritage.org
+*** Browsing
+    - =ls=
+    - =git log= (Linux kernel: 800K+ commits)
+*** Wayback machine
+    - tarball
+    - =git bundle= (Linux kernel: 7M+ nodes)
+*** Provenance tracking
+    - commit provenance (one/all contexts) \hfill note: requires backtracking
+    - origin provenance (one/all contexts)
+*** Note                                                    :B_ignoreheading:
+    :PROPERTIES:
+    :BEAMER_env: ignoreheading
+    :END:
+    Note: we therefore need both the direct Merkle DAG graph and its
+    *transposed*
+
+** Use cases --- research questions
+*** For the sake of it
+    - local graph topology
+    - connected component size
+      - enabling question to identify the best approach (e.g., scale-up
+        v. scale-out) to conduct large-scale analyses
+    - any other emerging property
+*** Software Engineering topics
+    - software provenance analysis at this scale is pretty much unexplored yet
+    - industry frontier: increase granularity down to the individual line of
+      code
+    - replicate at this scale (famous) studies that have generally been
+      conducted on (much) smaller version control system samples to
+      confirm/refute their findings
+    - ...
+** Exploitation
+   #+BEAMER: \LARGE \centering
+   How do you query the Software Heritage archive?
+   #+BEAMER: \Large \\
+   (on a budget)
+
+** The Software Heritage Graph Dataset                      :B_ignoreheading:
+   :PROPERTIES:
+   :BEAMER_env: ignoreheading
+   :END:
+   #+INCLUDE: "../../common/modules/dataset.org::#main" :minlevel 2 :only-contents t
+   #+INCLUDE: "../../common/modules/dataset.org::#morequery" :minlevel 2 :only-contents t
+
+** Sample study --- 50 years of gender differences in code contributions
+   - start from the Software Heritage graph dataset
+   - detect gender of author names using standard tooling (=gender-guesser=)
+   # - caveat: how to identify /first/ name?
+   - analyze both authors and commits over time, bucketing by commit timestamp
+   #+BEAMER: \begin{center} \includegraphics[height=0.45\textheight]{this/commits-pie.pdf} \includegraphics[height=0.45\textheight]{this/ratio-female-authors.pdf} \\ \scriptsize total commits by author gender (left), ratio of active female commiters over time (right)\end{center}
+*** 
+   #+BEGIN_EXPORT latex
+   \vspace{-1mm}
+   \begin{thebibliography}{} \footnotesize
+   \bibitem{Zacchiroli2021} Stefano Zacchiroli
+   \newblock Gender Differences in Public Code Contributions: a 50-year Perspective
+   \newblock IEEE Softw. 38(2): 45-50 (2021)
+   \end{thebibliography}
+   #+END_EXPORT
+
+** Discussion
+   - one /can/ query such a corpus SQL-style
+   - but relational representation shows its limits at this scale
+     - ...at least as deployed on commercial SQL offerings such as Athena
+   - note: (naive) sharding is ineffective, due to the pseudo-random
+     distribution of node identifiers
+   - experiments with Google BigQuery are ongoing
+     - (we broke it at the first import attempt..., due to very large arrays in
+       directory entry tables)
+
+* Graph compression
+ #+INCLUDE: "../../common/modules/graph-compression.org::#main" :minlevel 2 :only-contents t
+
+* Security synergies and outlook
+  #+INCLUDE: "this/security.org" :minlevel 2
+  #+INCLUDE: "this/roadmap.org" :minlevel 2
+
+** Wrapping up
+  #+latex: \vspace{-1mm}
+*** 
+    - Software Heritage archives all public source code as a huge Merkle DAG
+    - Querying and analyzing it at scale (20/200 B nodes/edges) is an open
+      problem
+    - Gold mine of research leads in sw. eng., big code, reproducibility,
+      security
+  #+latex: \vspace{-2mm}
+*** References (selected)
+  #+latex: \vspace{-1mm}
+  #+BEGIN_EXPORT latex
+  \begin{thebibliography}{}
+  \scriptsize
+
+  \bibitem{Abramatic2018} Jean-François Abramatic, Roberto Di Cosmo, Stefano Zacchiroli
+  \newblock Building the Universal Archive of Source Code
+  \newblock Communications of the ACM, October 2018
+
+  \bibitem{Pietri2019} Antoine Pietri, Diomidis Spinellis, Stefano Zacchiroli
+  \newblock The Software Heritage graph dataset: public software development under one roof
+  \newblock MSR 2019: 16th Intl. Conf. on Mining Software Repositories. IEEE
+
+  \bibitem{Boldi2020} Paolo Boldi, Antoine Pietri, Sebastiano Vigna, Stefano Zacchiroli
+  \newblock Ultra-Large-Scale Repository Analysis via Graph Compression
+  \newblock SANER 2020, 27th Intl. Conf. on Software Analysis, Evolution and Reengineering. IEEE
+
+  \end{thebibliography}
+  #+END_EXPORT
+*** Contacts
+    Stefano Zacchiroli / [[https://upsilon.cc/~zack/][upsilon.cc]] / [[mailto:zack@upsilon.cc][zack@upsilon.cc]] / [[https://twitter.com/zacchiro][@zacchiro]]
+
+* Appendix                                                       :B_appendix:
+  :PROPERTIES:
+  :BEAMER_env: appendix
+  :END:
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diff --git a/talks-public/2021-05-19-telecom-paris/this/roadmap.org b/talks-public/2021-05-19-telecom-paris/this/roadmap.org
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+** A (brief) research roadmap --- 1
+*** Graph compression
+    - incremental, amortized compression → ongoing UniMi collaboration
+    - graph query languages on top of the compressed representation → LIRIS
+      collaboration (early stages)
+  #+BEAMER: \vfill \pause
+*** Complex networks
+    - local topology of the global VCS graph
+    - emergent properties (the "classics": scale-free, small world, etc.)
+    - dynamic modeling of graph evolution over time → collab. with physics @
+      UParis
+*** 
+    #+BEGIN_EXPORT latex
+    \vspace{-2mm}
+    \begin{thebibliography}{}
+    \small
+    \bibitem{Pietri2019}  Antoine Pietri, Guillaume Rousseau, Stefano Zacchiroli\newblock
+    Determining the Intrinsic Structure of Public Software Development History\newblock
+    MSR 2020: 17th Intl. Conf. on Mining Software Repositories. IEEE\newblock
+    registered study protocol
+    \end{thebibliography}
+    #+END_EXPORT
+** A (brief) research roadmap --- 2
+  #+BEAMER: \vspace{-2mm}
+*** Very-large-scale "big code"
+    - /big code/ = apply ML/DL to source code and other development byproducts
+    - current results are language-specific and limited in scale; even the
+      simplest problems become challenging at this scale and heterogeneity
+      - lead: scalable language detection → collaboration with UniBo
+      - lead: project classification → collaboration with CELI
+    - the VCS graph remains largely unexplored in big code
+      - lead: use GNN for VCS node classification → ANR COREOGRAPHIE
+    #+BEAMER: \vspace{-1mm}
+***                                                         :B_ignoreheading:
+    :PROPERTIES:
+    :BEAMER_env: ignoreheading
+    :END:
+    #+BEAMER: \vspace{-1mm} \pause
+*** Very-large-scale source code indexing
+    - common AST-based approaches for code indexing are not viable here due do
+      maximum heterogeneity
+    - alternative: treat code as text and full-text index it
+      - previous exp.: 3-gram based indexing in Debsources, supporting regexp
+        matching
+    - goal: find a sweet spot between the two
+    #+BEAMER: \vspace{-1mm}
+** Recent results on (visual) programming language identification  :noexport:
+   #+BEGIN_EXPORT latex
+   \begin{thebibliography}{}
+   \small
+
+   \bibitem{DelBonifro2021a} Francesca Del Bonifro, Maurizio Gabbrielli, Stefano Zacchiroli
+   \newblock Content-Based Textual File Type Detection at Scale
+   \newblock ICMLC 2021: The 13th International Conference on Machine Learning and Computing. ACM, 2021 
+
+   \bibitem{DelBonifro2021b} Francesca Del Bonifro, Maurizio Gabbrielli, Antonio Lategano, Stefano Zacchiroli
+   \newblock Image-based many-language programming language identification
+   \newblock (under review)
+
+   \end{thebibliography}
+   #+END_EXPORT
+** A (brief) research roadmap --- 3
+*** Very-large-scale reproducibility in software engineering
+    - most results in empirical software engineering are determined on corpuses
+      significantly smaller than Software Heritage\\
+      → external validity threat; do results generalize to the full body of
+      public code?
+    - 2-year research plan
+      1) identify impactful sw. eng. studies that can be reproduced using
+         Software Heritage
+	 - selected topics (tentative): code reuse, code quality, project
+           classification, technical debt, developer productivity
+      2) reproduce selected studies one-by-one, at Software Heritage scale
+      3) document findings, e.g., via RENE (REproducibility Studies and
+         NEgative Results) scientific initiatives
+    - collaboration with Microsoft Research (just started)
diff --git a/talks-public/2021-05-19-telecom-paris/this/security.org b/talks-public/2021-05-19-telecom-paris/this/security.org
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+** Securing the open source supply chain
+
+   *Software supply chain attacks* are becoming more and more popular and
+   raising in profile. → Cf. /SolarWindws attacks/ (2021), breaching several US
+   govt. branches
+
+*** Definition --- Reproducible Builds (R-B)
+    The build process of a software product is *reproducible* if, after
+    designating a specific version of its source code and all of its build
+    dependencies, every build produces *bit-for-bit identical artifacts*, no
+    matter the environment in which the build is performed.
+
+*** 
+    - R-B allows to *increase trust in binary executables* built from trusted
+      (open source) code by untrusted 3rd-party software vendors (e.g., app
+      stores, distros)
+
+    - The *[[https://reproducible-builds.org/][reproducible-builds.org project]]* has popularized the notion, is
+      backed by major open source industry players, and has made large open
+      source software collections reproducible (e.g., 95% of Debian packages)
+
+*** References                                              :B_ignoreheading:
+    :PROPERTIES:
+    :BEAMER_env: ignoreheading
+    :END:
+    #+BEGIN_EXPORT latex
+    \begin{thebibliography}{}
+    \footnotesize
+    \bibitem{Lamb2021RB} Chris Lamb, Stefano Zacchiroli 
+    \newblock Reproducible Builds: Increasing the Integrity of Software Supply 
+    \newblock IEEE Software 2021 (to appear, DOI 10.1109/MS.2021.3073045)
+    \end{thebibliography}
+    #+END_EXPORT
+
+** Securing the open source supply chain (cont.)
+*** 
+    - Software Heritage provides key ingredients for R-B pipelines: on-demand
+      archival (e.g., of VCS commits referenced by build recipes) + long-term
+      availability
+    - We have implemented this by integrating the GNU Guix package manager with
+      Software Heritage
+
+***                                                         :B_ignoreheading:
+    :PROPERTIES:
+    :BEAMER_env: ignoreheading
+    :END:
+    #+BEAMER: \begin{center}\hfill\includegraphics[height=0.4\textheight]{swh-guix-1}\hfill\includegraphics[height=0.4\textheight]{swh-guix-2}\hfill~\end{center}
+    #+BEAMER: \scriptsize
+    - \url{https://www.softwareheritage.org/2019/04/18/software-heritage-and-gnu-guix-join-forces-to-enable-long-term-reproducibility/}
+    - \url{https://guix.gnu.org/blog/2019/connecting-reproducible-deployment-to-a-long-term-source-code-archive/}
+
+** Tracking of vulnerable source code artifacts
+
+*** 
+    Software Heritage provides a unique observatory on the (best approximation
+    of) the entire /Software Commons/, i.e., all software published in source
+    code form
+
+*** Software provenance tracking at the scale of the world
+    - by following the /transposed/ Software Heritage graph we can locate *all
+      known public occurrences* of source code artifacts (individual source
+      files, entier source tree, commits) in other commits or repositories
+
+    - we have developed two approaches to do that:
+
+      1. database-based (Rousseau et al. EMSE 2020): incremental, answers a
+         fixed set of queries, requires significant disk space
+
+      2. compressed-graph-base (Boldi et al. SANER 2020): non-incremental,
+         flexible graph-base querying, fits in RAM
+
+    - current applications: "intellectual property"/prior art, open source
+      license compliance, software composition analysis (SCA)
+
+** Tracking of vulnerable source code artifacts (cont.)
+
+*** Adding in-memory commit timestamps (experimental)
+    Idea: in-memory timestamp array (us precision, 8 bytes each), indexed by
+    revision node id. This enables to efficiently exploit timestamp information
+    during graph visits.
+
+*** Finding the /earliest/ commit referencing a source file/dir
+    Early experiment: finding the earliest revision containing a given file
+    using in-memory commit timestamps, on 10 M randomly selected blobs.
+
+    Mean lookup time: 4.1 ms (avg on 95% percentile: 2.2 ms)
+
+*** Tracking vulnerable source code files/trees
+    Given a source file/tree affected by a known vulnerability (e.g.,
+    identified by a CVE) we can efficiently identify /all/ commits (and
+    repositories, extending the traversals) that reference it, triggering
+    further inspection. Furthermore, we can efficiently select which commits to
+    filter out during visits, based on commit timestamps of other attributes
+    that can be made to fit in memory (or memory mapped to disk).
+
+** Tracking of vulnerable source code artifacts (cont.)
+
+*** v. State-of-the-art industry offerings
+    Similar to what GitHub/GitLab offer as a service, but:
+
+    - without having to rely on repository scanning, because the "big picture"
+      is already present in the Software Heritage archive by design
+
+    - independent from the development platform vendor (e.g., a "vulnerable
+      file" primarily hosted on GitHub can be spotted in GitLab repositories
+      and vice-versa)
+
+    - complementary and synergistic with analyses of vulnerable dependency
+      information (which are also available in Software Heritage via metadata
+      mining)
+
+*** Caveats
+
+    - current granularity stops at the file level and traceability breaks with
+      even just whitespace changes. Increasing tracking granularity to the
+      snippet/line of code level is possible, but untested at this scale yet
+      (cf. research roadmap)
diff --git a/talks-public/2021-05-19-telecom-paris/this/zack.org b/talks-public/2021-05-19-telecom-paris/this/zack.org
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+
+** About me
+   - Associate Professor (/Maître de conférences/), Université de Paris
+   - on leave (/délégation/) at Inria
+   - Free/Open Source Software activist (20+ years)
+   - Debian Developer & Former 3x Debian Project Leader
+   - Former Open Source Initiative (OSI) director
+   - Software Heritage co-founder & CTO
+
+  #+BEAMER: \vfill \pause
+
+*** Research path
+    1) Formal methods for ensuring the quality of software upgrades (Mancoosi
+       project)
+
+       Industry adoption: Debian, OPAM, Eclipse P2
+    2) Formal methods for automated upgrade planning in the cloud (Aeolus
+       project)
+
+       Industry adoption: Mandriva, Kyriba
+    3) Large-scale software evolution analysis (Debsources platform)
+    4) Very-large-scale source code analysis and preservation (Software
+       Heritage)
+
+       → this talk