21 Matching Annotations
  1. Last 7 days
    1. So what can we do? }Alternative? Synchronous models? BUT REAL, PRACTICAL SYSTEMS ARE NOT SYNCHRONUS !!! }Use randomization, probabilistic guarantees }Process groups: sacrifice liveness under the assumption that retransmissions will eventually be received from good participants, the protocol eventually terminates }Avoid consensus, use quorum systems

      resolução do problema de consenso em sistemas distribuídos assíncronos

    2. }Agreement: all non-faulty processes decide on the same value }Validity: if a process decides on a value, then there was a process that started with that value }Termination: A non-faulty process decides in a finite time

      propriedades de um algoritmo de consenso

    3. In an asynchronous system, a process pi cannot tell whether a non-responsive process pj has crashed or it is just slow

      o problema de consenso em sistemas assíncronos

    1. Technically, solving the asynchronous distributed consensus problem in bounded time is impossible. As proven by the Dijkstra Prize–winning FLP impossibility result [Fis85], no asynchronous distributed consensus algorithm can guarantee progress in the presence of an unreliable network.

      o problema de consenso em sistemas distribuídos assíncronos é impossível de resolver

    2. Distributed consensus algorithms may be crash-fail (which assumes that crashed nodes never return to the system) or crash-recover. Crash-recover algorithms are much more useful, because most problems in real systems are transient in nature due to a slow network, restarts, and so on. Algorithms may deal with Byzantine or non-Byzantine failures. Byzantine failure occurs when a process passes incorrect messages due to a bug or malicious activity, and are comparatively costly to handle, and less often encountered.

      modelos de falha considerados

    3. asynchronous distributed consensus, which applies to environments with potentially unbounded delays in message passing

      interesse apenas em sistemas assíncronos

    4. The logic is intuitive: if two nodes can’t communicate (because the network is partitioned), then the system as a whole can either stop serving some or all requests at some or all nodes (thus reducing availability), or it can serve requests as usual, which results in inconsistent views of the data at each node.

      Resume a lógica do teorema CAP

    5. CAP Theorem

      Descreve propriedades fundamentais de um sistema distribuído.

  2. Jun 2019
    1. EthereumEthereum is a distributed computer; each node in the network executes some bytecode (hint: Smart Contracts), and then stores the resulting state in a blockchain. Due to the properties of the blockchain representing application state, this results in “applications that run exactly as programmed without any possibility of downtime, censorship, fraud or third party interference”.

      This is a decent little explanation for how smart contracts execute on blockchains. Author missed in "Due to the properties of the blockchain" to say that all nodes must also come to consensus about how the code was executed and therefore "applications that run exactly...". We will later discuss deterministic code execution in relation to this

  3. Jan 2019
    1. The great thing about proof is that it requires no belief. Don't believe, verify!

      <big>评:</big><br/><br/>比特币工程师 Lopp 的此番回应是一件很刺激的事情,就像听到尼采说「上帝死了」一样令人激动。在 19 世纪,便有人说:「上帝是一个无用而且很花钱的假设,因此我们不需要他」。200 年后,依然有人扛着如是的观点大旗在卖力宣扬革命。这说明什么?<br/><br/>说明后资本主义时代,人的精神依然处于被压迫、剥削、异化的状态。价值是必须能够被验证的东西,and that's why we have fewer and fewer nice things.

    1. Second, the majority cannot change the rules of Bitcoin. In a sense, they can create new consensus rules, but that would be a hard fork, which requires everyone to upgrade. They’re free to try to convince the rest of the network that their rules are better, but as sovereign individuals, Bitcoin users have no obligation to follow such rules. The power of whom to follow lies entirely with the owner of the node.

      <big>评:</big><br/><br/>What did Jimmy specifically mean when he talked about the group of “Bitcoin users”? And similarly, how to define the gap between the military and the civilian when we talk about some certain power to follow?<br/><br/>可供参考的是,在《人性的弱点》一书里,作者卡耐基反复强调着「人始终只关注自己的利益」。更好的规则?更好的秩序?在利益面前皆为浮云。选择站队的权力确实由个体掌握,但这并不影响到权力是否会被团体以违背个体意志的方式行使。更何况个体意志并不总是「弱者」的代名词,「作恶」也绝非市场垄断者一家之嫌。

  4. Aug 2018
    1. visualizations are more than just ‘‘prettypictures’’: rather, precisely in virtue of their bringinginto play oursharedcognitive and aesthetic frame-works as human beings, they thereby catalyze theepistemological – but also aesthetic and therebysocial, if not also political – processes that create ashared intersubjective framework in the first place,one that then makes possible trust-building and asharedsensus communiswithin which the enterpriseof collaborative science may take place
  5. Jun 2018
    1. By requiring a lock up period for the DCR to obtain tickets, Decred hopes that only users invested in the long-term growth of the network will be involved in the consensus process. Short-term speculators and day traders of DCR will not be able to participate in consensus or governance without making their holdings illiquid.
  6. May 2018
  7. Feb 2018
    1. The Bottom Line is that you will benefit from using the community group

      Unlike other approaches to learning new PM concepts that span many disciplines and competencies, we help you focus on your strengths and concerns within groups, while developing a holistic solution, that optimally increases your competitive advantage.

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  8. Jul 2016
    1. The problem, said Ward, was that wiki was a relentless consensus engine. And for certain things (e.g. encyclopedias) that might not be a bad thing, but as a way of working it had its drawbacks.

      I'm fascinated by this point.

      This was/is one of the critiques of (Rap) Genius as well: hip as its authoritative voice was, it nonetheless moved toward the encyclopedia. Though the company has since pivoted to allow more individual commentary than encyclopedic exposition--I don't think they've quite worked this out in the UI yet--the original site, and the part I think that is still most compelling was the Wikipedia for rap lyrics.

      But from a pedagogical perspective, that expository mode of analysis was really only one, and perhaps not even the most important, use of collaborative annotation. For my part, I allowed teachers to duplicate texts and create their own versions, instructing their students to annotate however thy wanted them to: authoritatively, discursively, inquisitively, with GIFs.

  9. Apr 2016
  10. Nov 2015
  11. Aug 2015
    1. The Aspen Consensus, in a nutshell, is this: the winners of our age must be challenged to do more good. But never, ever tell them to do less harm.

      Spot on.