Where

INRIA (Paris)
23, avenue d'Italie
75013 Paris

Meeting will take place in Room Bleu 1 (6 Floor)

INRIA (Place d'Italie)

Day One

Sessions

9:30am 10:00am Arrival / "Tour de table"
10:00am 11:00am Replication / Algorithms
11:00am 11:30am break
11:30am 12:30pm Replication / Algorithms 2
12:30pm 1:30pm lunch
1:30pm 3:00pm Replication / Theory
3:00pm 3:30pm break
3:30pm 5:00pm Replication / Theory 2

Participants

SCORE: Gérald Oster, Luc André, Pascal Urso, Mehdi-Ahmed Nacer, Hyun-Gul Roh
REGAL: Marc Shapiro, Marek Zawirski, Masoud Saeida Ardekani, Pierpaolo Cincilla, Lokesh Gidra, Mesaac Makpangou
CASSIS: Abdessamad Imine, Hoang Bao Thien
ASAP: Stéphane Weiss
XWiki SAS: Fabio Mancinelli
GDD: Pascal Molli
UNL: Nuno Preguica

Designing an advanced CRDT: a graph data structure for asynchronous processing of web data

Presenter: Nuno Preguiça Documents: PDF

Notes.

Graph CRDT
Web structure represented as directed graphs
Web evolves therefore the graph has to be updated
Web pages processed concurrently by multiple servers / incremental processing

State-based solution (based on observed-remove sets)
Two sets: nodes + arcs
Operations:

  • (updates): addNode(n), removeNode(n), addArc(n1, n2), removeArc(n1, n2)
  • query (reads): lookupArc((n1,n2))


Garbage collection mechanism based on state vectors to avoid tombstones
Snapshots management mechanism computed using state vectors

  • useful for? support access to consistent data in transactions and data evolution history

    Pascal U.: gc looks like the managenement in logoot? why don’t use URI/URL as unique identifier? because the referenced content can be added/removed multiple times, remove operation removes all observed uids associated to an URL.
    Marc: You cannot remove immediately, right?
    Nuno: No I can.
    Abdessamad: What about versions vectors limitations?
    Nuno: In our context, cloud computing, we know the limited number of clusters and their unique identifier
    Pascal M: So, basically, the scope of applications of CRDT has been reduced. At the beginning Woot/Logoot were proposed for peer-to-peer networks. You can use consensus in this context, no?
    Nuno: Well consensus might not be suitable. For instance Amazon does not use consensus (may be because of data-centers spread over the world).
    Marc: If you want high-performance you can’t put consensus in your loop
    Nuno: cloud computing literature states optimistic replication is used

C-Set: A Commutative Replicated Data Type for Semantic Stores

Presenter: Pascal Molli Documents: PDF

Notes.

Presented at REsource Discovery 2011 workshop (http://ldc.usb.ve/~mvidal/RED2011/) co-located with Extended Semantic Conference (ESWC 2011).

Context: Social web is adopting semantic technologies and is generating massive new semantic datasets.
Challenge: synchronizing semantic stores (very large data sets, autonomous participants, etc.)

CRDT for semantic store: semantic data can be represented as sets of triples.
Need a CRDT for sets.
Set (real semantic) is not a CRDT.

Proposal: C-Set
S = {(e, count) : e \in elements, count \in Z}
local operations: ins(e: element), del(e:element)
remote operations: rins(e:element, k: Z), rdel(e:element, k: Z)
Current proposal does not preserve intentions (see counter-example)
Marc: Did you try OR-set?
Pascal M.: yes, i think it will work, but we will loose on another point (vectors? tombstones?)

Telex Light: a platform for cooperative social applications

Presenter: Pierpaolo Cincilla Documents: PDF Δ

Notes.

Telex: A communication infrastructure for collaborative nomadic applications
Demo

The cost of consistency in large-scale replication

Presenter: Masoud Saeida Ardekani Documents: PDF Δ

Notes.

Full replication, partial replication (atomic broadcast), genuine replication (atomic multi-cast)
Snapshot isolation (read latest snapshot), generalized snapshot isolation (read any snapshot)
Consistent snapshots are determined using concurrent version vectors

Generalized snapshot isolation (GSI) : snapshot monotonicity

Read-write dependence vector (RWDV)

More scalable than other Genuine approach-based systems (due to relaxing of monotonicity), or partial replication-based (latency greater due to atomic broadcast requirement).

Asynchronous re-balancing of a replicated tree

Presenter: Marek Zawirski Documents: PDF

Notes.

Delta (previous work) : Novel catch-up mechanism based on symbolic positions

State of the art in using semantic information to ensure consistency

Presenter: Marek Zawirski Documents: PDF

Notes.

Bloom [Alvaro et al. 2011]: Use monotonic logic programming model to encourage create pieces of program can run concurrently. What about writing/expressing CRDT in Bloom? http://www.bloom-lang.net/

ESCOPADS: Earth-SCalewams sets. : Mares:eiv class='vspa))auea>: Marek Zawirski Notes.

Delta (previous work) :amye 0,xin es gtem/crawle06-09-M/iv ectors

State of the art in sions Replication / Theory

Participants

SCORE: Gérald Oster, Luc André, Pascal Urso, Mehdi-Ahmed Nacer, Hyun-Gul Roh
REGAL: Abdessamad Imine, HoanMilicëGALtionowi on/>ASAP: Stéphane Weiss
XWiki SAS: Fabio Mancinelli
GDD: Pascal Molli
UNL: Nuno Preguica

Designing an advanced EPDF

Notes.

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Telex: A communicationliteraogrrement, k: Zconcueft;nomd ic aptors

9:30am 10:00am Replication / AlgorithE 10:00am 10:00am break
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12:30pm
1:30pm lunch
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ESCOPADS: Earth-SCalewp (: Masoud Saeida Ardekani>GDD:Notes.

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Notes.

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Delta (previous work) http://www.bloom-lang.net/

Day One

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