超级账本官方教程第二章介绍（翻译）

超级账本在 edx 上的在线课程第二章，根据自己的理解进行了总结。对一些个人觉得学习区块链技术关系不大的章节进行了省略。

Hyperledger

Hyperledger is a group of open source projects focused around cross-industry distributed ledger technologies. Hosted by The Linux Foundation, collaborators include industry leaders in technology, finance, banking, supply chain management, manufacturing, and IoT.

As of October 2017, Hyperledger consists of eight projects, five of which are distributed ledger frameworks. The other three projects are modules that support these frameworks.

As Arnaud Le Hors, member of the Hyperledger Technical Steering Committee, emphasized,

“these projects show how broadly applicable blockchain technology really is. This goes way beyond cryptocurrencies”.

Hyperledger provides an alternative to the cryptocurrency-based blockchain model, and focuses on developing blockchain frameworks and modules to support global enterprise solutions. The focus of Hyperledger is to provide a transparent and collaborative approach to blockchain development.

超级账本是由Linux Foundation主导的开源项目，截止到2017年10月主要包含八个项目，其中包含五个框架以及三个为框架项目提供支持的组件项目。超级账本项目的目的是为全球企业提供一个商业化的区块链整体解决方案。

Comparing Hyperledger with Bitcoin and Ethereum

The following table explores the differences between Hyperledger’s permissioned distributed ledgers and the Bitcoin and Ethereum permissionless blockchains. If you are considering blockchain solutions for your business requirements, it is important to pay attention to all these elements and weigh in on those that are most important for your use case.

	Bitcoin	Ethereum	Hyperledger Frameworks
Cryptocurrency based	Yes	Yes	No
Permissioned	No	No	Yes (in general)*
Pseudo-anonymous	Yes	No	No
Auditable	Yes	Yes	Yes
Immutable ledger	Yes	Yes	Yes
Modularity	No	No	Yes
Smart contracts	No	Yes	Yes
Consensus protocol	PoW	PoW	Various**

*Sawtooth can be configured to be permissionless

**Key Hyperledger consensus protocols are Apache Kafka in Hyperledger Fabric, PoET in Hyperledger Sawtooth, RBFT in Hyperledger Indy, Tendermint in Hyperledger Burrow, and Yet Another Consensus (YAC) in Hyperledger Iroha. For more details, see the Hyperledger Architecture, Volume 1 paper.

超级账本与比特币及以太坊的区别：

1. 超级账本不是基于数字加密货币
2. 超级账本是基于授权的区块链网络（联盟链）（`Sawtooth框架也同时支持未授权）
3. 超级账本的整体设计趋于模块化，方便功能的插拔及定制化。
4. 超级账本的共识机制有多种选择，但都不同于其他两种公有链目前使用的 POW 算法。

Blockchain for Business

The cryptocurrency-based blockchain model, popularized by public blockchains like Bitcoin and Ethereum, currently falls short of fulfilling a host of requirements that many types of organizations would have to fulfill in order to be compliant when using blockchain and distributed ledger technologies - for instance, in the areas of financial services, healthcare, and government.

Hyperledger is a unique platform that is developing permissioned distributed ledger frameworks specifically designed for enterprises, including those in industries with strong compliance requirements. Enterprise use cases require capabilities such as scalability and throughput, built-in or interoperable identity modules for the parties involved in a transaction or a network, or even access to regulators who can access all data in the ledger as read-only to ensure compliance. The latter is particularly important because, regardless of the innovation, it has to operate within the current regulatory framework, as well as comply with any new rules that come into place specifically targeted at blockchain technologies.

The enterprise continues to be at the heart of this course.

对于基于加密货币的比特币，以太坊及其他类似的公有链而言，由于需要考虑公有链无需授权的特征带来的额外安全方面的隐患，公有链在性能上做出了比较大程度的牺牲，所以导致目前觉得部分公有链的性能都不能满足大型公司业务对区块链应用性能的要求。

超级账本由于基于授权的特征，安全隐患方面的降低使得超级账本的性能上较公有链有比较大的提升。另外对于企业应用的可扩展性，吞吐量，模块化等特性的需求，超级账本也提供了大量的支持。

Incubated Hyperledger Projects

超级账本项目孵化器

1. What are the projects currently being incubated by Hyperledger?
2. So, at Hyperledger, we have a total of eight different projects, actually, as of this week [October 2017].
3. Because we always have the door open to new projects joining.
4. And we evaluate those projects on, you know, how do they fit with the portfolio of other projects,
5. are they mature enough to really understand, you know, where they’re going to go and who the developers are around them…
6. But, every new project that comes in, comes in through something called the Incubator, right?
7. Because we figured there’s a period of time where we need to do a number of things:
8. we need to make sure that all of the intellectual property associated with that code is actually being contributed correctly,
9. and, more importantly, we need to make sure that the development team that is coming along with that code understands how to use the tools,
10. but also understands how to work collaboratively and publicly. Alright?
11. This is sometimes a new thing for many of these types of projects.
12. So, Fabric has graduated from the Incubator, to be an ordinary full-fledged project in Hyperledger.
13. Sawtooth has graduated as well. [Iroha has also graduated from the Incubator.]
14. The other projects are still working through that process, and the goal is to get every one of the projects through.
15. We don’t try to apply a flamethrower to, like, nudge them through too strongly, right?
16. But, you know, the hope is that, over time, that they do become that,
17. and that becomes yet another trademark, a signal to the public that this is now code that they can trust, right?
18. That this is now something they can build upon.
19. And so, that’s one of these stages. Another one is, for example, releasing as 1.0, which the Fabric community did a few months ago.
20. So, we have all these signals that we hope to be able to send to the public, and these other projects are still on that path.

超级账本项目目前有八个子项目（五个框架+三个模块），其中Fabric和Sawtooth已经发布1.0版本，标志着基本可以商用，其他项目还在不断完善中。

Components of Hyperledger Frameworks

Hyperledger business blockchain frameworks are used to build enterprise blockchains for a consortium of organizations. They are different than public ledgers like the Bitcoin blockchain and Ethereum. The Hyperledger frameworks include:

• • An append-only distributed ledger
  • A consensus algorithm for agreeing to changes in the ledger
  • Privacy of transactions through permissioned access
  • Smart contracts to process transaction requests.

超级账本商用项目致力于联盟链。与比特币的公有链不同。超级账本的框架包括：

• 一个增量的分布式账本
• 一个在账本内容发生变化时需要的共识协议
• 基于授权的交易隐私性管理机制
• 基于智能合约的交易收发流程（具体业务逻辑）

Hyperledger Iroha v0.95

Hyperledger Iroha is a blockchain framework contributed by Soramitsu, Hitachi, NTT Data, and Colu. Hyperledger Iroha is designed to be simple and easy to incorporate into infrastructure projects requiring distributed ledger technology. Hyperledger Iroha emphasizes mobile application development with client libraries for Android and iOS, making it distinct from other Hyperledger frameworks. Inspired by Hyperledger Fabric, Hyperledger Iroha seeks to complement Hyperledger Fabric and Hyperledger Sawtooth, while providing a development environment for C++ developers to contribute to Hyperledger.

In conclusion, Hyperledger Iroha features a simple construction, modern, domain-driven C++ design, along with the consensus algorithm YAC.

Iroha 项目是由几个日本（Soramitsu, Hitachi, NTT Data）和以色列（Colu）公司公司主导的，致力于移动端（Android 和 IOS）的框架。受 Fabric 和 Sawtooth 项目的启发,希望为使用 C++ 的开发者提供一个超级账本的框架。其默认的共识协议采用 YAC。

Introduction to Hyperledger Sawtooth (Courtesy of Sawtooth)

用海鲜食品溯源为例，介绍 Sawtooth 项目的应用场景

Meet Rich: he owns a popular seafood restaurant in Boston, Massachusetts.

Rich strives to serve only the freshest, highest quality fish to his patrons,

but he often has difficulty knowing exactly where it was caught, how it got to his restaurant, or if it’s even the right species of fish.

From ocean to table, the fish supply chain is difficult to track, and usually follows this pattern:

the fish is caught by a commercial fisherman in the ocean,

the fisherman then sells the fish to a market, processor, or broker,

a distributor then transports the fish to a restaurant or grocery store for a consumer to purchase.

Rich typically only buys from one or two fish distributors that he has built a foundation of trust and personal history with.

He’d like to expand his menu by adding some different kinds of seafood from other distributors,

but he worries about integrity, and for good reason.

He recently read a study by Oceana, which showed that 33% of fish purchased from retail outlets is incorrectly labeled,

and that illegal fishing represents losses between 10 to 23 billion dollars worldwide.

Rich knows that mislabeled and illegally sourced fish could hurt his customers,

his restaurant’s reputation, and the environment of our planet.

Fortunately for Rich and others in the seafood industry,

Sawtooth Lake blockchain technology can provide an immutable record of the provenance and lineage of various goods, like fish.

In combination with Internet of Things-enabled sensors, Sawtooth Lake can manage the ownership and journey of fish from ocean to table.

Sensors can be attached to fish the moment they are harvested,

immediately and continuously recording data such as the location and temperature of the fish.

Now, Rich can validate when and where his fish was caught, and that it was stored properly on ice while it was transported.

The Sawtooth Lake platform can also manage the Chain of Custody fish,

enabling ownership to be transferred and traded on the blockchain according to smart contracts.

With Sawtooth Lake as a traceability blockchain, Rich can easily see which fishermen meet his quality standards and feels comfortable doing business with new tradesmen.

When he serves up a new special to a cherished customer, he can confidently and accurately assure her

it’s the type of fish she ordered, it was stored at safe temperatures, when and where it was caught, how long it took to get to her plate, and the fish’s name… just kidding.

Sawtooth Lake blockchain technology can be used for a wide variety of applications,

from capital markets to international trade.

The Internet of Things ties the physical world to the digital world,

with Sawtooth Lake recording the generated data in a way that all parties can trust its accuracy and completeness.

This is extremely useful for tracking perishable goods, like fish.

These sensors can track many key parameters, such as location, temperature, humidity, motion, shock, and tilt.

This technology could be added to any package or sensitive good you’re entrusting to other parties.

The blockchain will ensure the data is secure and tamper-proof, so that you know what you’re getting, and that you get what you pay for.

Sawtooth Lake creates a digital platform enabling physical traceability in a trustless world.

用一个海鲜食品溯源的例子，介绍了Sawtooth框架的应用场景

Hyperledger Sawtooth

Hyperledger Sawtooth, contributed by Intel, is a blockchain framework that utilizes a modular platform for building, deploying, and running distributed ledgers. Distributed ledger solutions built with Hyperledger Sawtooth can utilize various consensus algorithms based on the size of the network. By default, it uses the Proof of Elapsed Time (PoET) consensus algorithm, which provides the scalability of the Bitcoin blockchain without the high energy consumption. PoET allows for a highly scalable network of validator nodes. Hyperledger Sawtooth is designed for versatility, with support for both permissioned and permissionless deployments.

Sawtooth是由Intel 公司主导的区块链框架， 基于Sawtooth框架的区块链项目可以根据业务的规模自行选择不同的共识机制。默认共识机制采用 PoET，减少了能量的消耗，可用于授权/非授权 区块链部署。

####Sawtooth的主要特征

sawtooth 的主要特征

Some unique characteristics of Hyperledger Sawtooth are: one, I think we are the only Hyperledger project that provides distributed state agreement, and that’s a mouthful. But what it means is that you can trust that every node in the system has the same understanding of information, that you don’t have nodes that are, say, computing interest differently than a different computer on the network, and are gradually changing their database so that it’s no longer really in agreement with the rest of them. Something else that’s unique about Sawtooth is we thought a lot about our transaction processing interface, and we’re now able to create adapters for any kind of transaction logic. This was evidenced recently by our integration with Hyperledger Burrow. And you can now run any kind of Ethereum Virtual Machine code, like Solidity, for example, you can compile that and run that on Sawtooth. So, when you think about where is a home for things inspired by Ethereum or Solidity code created for Ethereum, how would you deal with that in an enterprise environment, you think Sawtooth and Burrow is the answer for that.

主要特征：

1. 唯一一个采用分布式共识机制的框架。
2. 为不同交易的接口 api 提供了统一的适配器。（Hyperledger Burrow 由此也是由此产生的）。
3. 如果想在 Hyperledger 项目内运行 Ethereum 编译器的代码，Sawtooth 和 Burrow 框架是合适的选择。

####Hyperledger Sawtooth Characteristics Relative to Use Cases (Dan Middleton)

符合 Sawtooth 特性的相关用例

1. So, unique characteristics of Sawtooth… There’s several, but one that comes to mind for a provenance or supply chain use case,
2. is that that network will probably grow over time.
3. The reason that a lot of us are starting blockchain networks, a lot of companies are invested in looking at blockchain networks,
4. because we think that we’re going to be in them for a long time and they’re going to continue to grow.
5. Sawtooth is designed so that you can grow the size of the network,
6. you can actually change the consensus mechanism on the fly…
7. I think this is a unique characteristic of Sawtooth amongst all of the other ledgers…
8. you can submit as a transaction and then have a policy within your network to accept that new consensus,
9. and then, your network can move from say a PBFT-style consensus to something like PoET, or some sort of random leader election consensus…
10. It allows you to have tens, or hundreds, or potentially thousands of different nodes on your network,
11. and you really can’t beat that kind of availability and integrity guarantees, or that kind of flexibility for a network that needs to be up for years.

1. Sawtooth特别适合供应链溯源等领域，他对整个应用的扩展性支持特别好，可以随意的增加节点的个数。
2. 可以轻易的通过构建并发送交易的形式更改整个应用的共识机制。
3. 可以允许整个网络存在数以千计的节点，同时依旧保证区块链网络的可扩展性，稳定性，完整性以及弹性。

Hyperledger Fabric v1.0

Hyperledger Fabric was the first proposal for a codebase, combining previous work done by Digital Asset Holdings, Blockstream’s libconsensus, and IBM’s OpenBlockchain. Hyperledger Fabric provides a modular architecture, which allows components such as consensus and membership services to be plug-and-play. Hyperledger Fabric is revolutionary in allowing entities to conduct confidential transactions without passing information through a central authority. This is accomplished through different channels that run within the network, as well as the division of labor that characterizes the different nodes within the network. Lastly, it is important to remember that, unlike Bitcoin, which is a public chain, Hyperledger Fabric supports permissioned deployments.

"If you have a large blockchain network and you want to share data with only certain parties, you can create a private channel with just those participants. It is the most distinctive thing about Fabric right now."

Brian Behlendorf, Executive Director of Hyperledger, The Linux Foundation

Fabric是由Digital Asset, Blockstream 和 IBM 公司相关的部分主导的框架。特点如下：

1. 所有的组件（例如共识机制，成员管理）都是优先考虑可插拔的形式，便于使用者选择不同的实现方式。
2. 采用通道（channel）的形式，实现了数据通信的隐私性处理，在一个通道里传播的交易，只有该通道授权过的参与方才能接收到。
3. Fabric 只支持基于授权的区块链网络。

What Is Unique about Hyperledger Fabric? (Chris Ferris)

Fabric 的特点

1. Well, I think, again, the primary distinction that we have with Hyperledger Fabric is that it is an implementation of a permissioned blockchain distributed ledger technology.
2. And this is independent, or distinguished from implementations such as Bitcoin and Ethereum,
3. and various others, that are essentially public, permissionless networks, where everybody can join anonymously.

Hyperledger Indy (Nathan George)

Indy 项目介绍

1. The Hyperledger consortium has many different projects that focus on different aspects of how ledgers can work and what use cases they can be applied for.
2. Hyperledger Indy is a distributed ledger purpose-built for doing distributed identity,
3. and what that means is, it allows you to have a route of trust to manage the keys, schemas, proofs, and other information that you need to,
4. in order to enable trusted peer interactions between different identities, as stored on a Hyperledger Indy blockchain instance.
5. So, if you have an identity it belongs to you, and only you, and no one can pull the plug on you.
6. And you can use that identity to manifest different correlatable pieces of data between you and other identities you want to interact with,
7. without leaking private information or disclosing information that you don’t want shared across all those different aspects of who you are.
8. And when you control your identity, it makes it so that you are also a party to the kinds of data sharing, claims, and proofs that can be made about you,
9. as information is shared across all the different interactions you might do online.
10. One of the main use cases of Hyperledger Indy is to create a global public utility for identity that’s being created by the Sovrin Foundation,
11. which allows us to take these identifiers, and to anchor them on a public ledger,
12. so that different pieces of truth or pieces of information can be trusted and shared with other people across the world,
13. and they can be trusted and validated, so that self-attested data can be shared, as well as third-party attestations can be shared across all kinds of interactions and across all kinds of data silos,
14. and what this makes possible is the ability to no longer have to function as an identity provider as a business,
15. but to rather let users authenticate based on the attributes that they’re willing to store and share themselves,
16. which allows for GDPR-compliant use cases, where you’re expressing consent on behalf of the user, and also reducing the amount of liability contained within a business,
17. because the data can be kept with the user and presented to you again in a way that you can trust and validate,
18. that what has been said, really was said, and is trusted by the other parties you do business with.

Indy 框架致力于基于区块链技术的分布式身份认证体系，以及基于身份认证的其他业务应用。

Hyperledger Indy

Hyperledger Indy is a distributed ledger purpose-built for decentralized identity. Hyperledger Indy’s goal is to achieve this by developing a set of

“(…) decentralized identity specs and artifacts that are independent of any particular ledger and will enable interoperability across any DLT that supports them.”

Contributed by the Sovrin Foundation, Hyperledger Indy allows individuals to manage and control their digital identities. Rather than having businesses store huge amounts of personal data of individuals, Hyperledger Indy allows businesses to store pointers to identity. Once the company verifies the other party’s identity, it throws it away.

According to Brian Behlendorf,

“(…) identity is a toxic asset that could present a liability to organizations.”

Indeed, since 2013, over 9 billion data records were lost or stolen. What is striking is that, out of these, only 4% were encrypted, and hence, rendered useless after being stolen (also called ‘secure breaches’). You can find detailed statistics at http://breachlevelindex.com/.

One of the key principles of Hyperledger Indy is its ‘Privacy by Design’ approach. Given the immutable nature of the DLT, it is all the more important that digital identities be handled with the utmost care, keeping human values front and center.

“Hyperledger Indy lets users authenticate identity based on the attributes they are willing to store and share themselves. This can reduce the amount of liability contained within a business because the data can be kept with the user and presented to you again in a way that you can trust and validate that what has been said really was said and is trusted by the other parties you do business with.”

- Nathan George, Maintainer, Hyperledger Indy

Further information about the history of the project can be found at https://sovrin.org/.

同上介绍，Indy 框架致力于基于区块链的加密数字身份。

Hyperledger Burrow v0.16.1

Formally known as eris-db, Hyperledger Burrow was released in December 2014. Currently under incubation, Hyperledger Burrow is a permissionable smart contract machine that provides a modular blockchain client with a permissioned smart contract interpreter built- in part to the specification of the Ethereum Virtual Machine (EVM). It is the only available Apache-licensed EVM implementation.

Following are the major components of Burrow:

• • The Gateway provides interfaces for systems integration and user interfaces
  • The Smart contract application engine facilitates integration of complex business logic
  • The Consensus Engine serves the dual purpose of:
    a. Maintaining the networking stack between the nodes, and,
    b. Ordering transactions
  • The Application Blockchain Interface (ABCI) provides interface specification for the consensus engine and smart contract application engine to connect.

You can learn more about Hyperledger Burrow at https://monax.io/platform/db/.

Burrow 框架是一个基于授权的智能合约虚拟机，其模块化的区块链客户端提供了针对以太坊虚拟机的内置解释器。具体的特性… 懒得翻译了，自己看。

Hyperledger Modules

The Hyperledger frameworks which we examined in the previous section are used to build blockchains and distributed ledgers. The Hyperledger modules, which we will look at next, are auxiliary softwares used for things like deploying and maintaining blockchains, examining the data on the ledgers, as well as tools to design, prototype, and extend blockchain networks.

超级账本的框架项目用于开发真正的区块链项目，而组件项目则定位于为区块链项目提供开发便利的模块化应用。

Hyperledger Cello

For businesses that want to deploy Blockchain-as-a-Service, Hyperledger Cello provides a toolkit that fulfills this need. Particularly for lean businesses and small enterprises, who want to reduce or eliminate the effort required in creating, managing, and terminating blockchains, Hyperledger Cello allows blockchains deployment to the cloud. Operators can create and manage such blockchains through a dashboard, and users (typically, chaincode developers) can obtain a blockchain instance immediately.

As a Hyperledger module, “Cello aims to bring the on-demand ‘as-a-service’ deployment model to the blockchain ecosystem”, thus helping in furthering the development and deployment of Hyperledger’s frameworks. Hyperledger Cello was initially contributed by IBM, with sponsors from Soramitsu, Huawei, and Intel.

Application developers and system administrators using Cello can provision and maintain Hyperledger networks. For instance, you can create a group of distributed ledger networks in virtual clouds known as ‘container clusters’, and then, manage and monitor those networks with a configurable dashboard. Additionally, you can build a Blockchain-as-a-Service (BaaS) platform.

Hyperledger Cello (Source: https://www.hyperledger.org/blog/2017/01/17/hyperledger-says-hello-to-cello)

Cello 组件为 BaaS（blockchain as a service） 提供了一个云服务解决方案。使得开发者不用在服务器上自己部署超级账本，取而代之可以直接以可视化面板的方式来操作云服务的区块链系统。

Hyperledger Explorer

Hyperledger Explorer is a tool for visualizing blockchain operations. It is the first ever blockchain explorer for permissioned ledgers, allowing anyone to explore the distributed ledger projects being created by Hyperledger’s members from the inside, without compromising their privacy. The project was contributed by DTCC, Intel, and IBM.

Designed to create a user-friendly web application, Hyperledger Explorer can view, invoke, deploy, or query:

• • Blocks
  • Transactions and associated data
  • Network information (name, status, list of nodes)
  • Smart contracts (chain codes and transaction families)
  • Other relevant information stored in the ledger.

The ability to visualize data is of critical importance, in order to extract business value from it. Hyperledger Explorer provides this much needed functionality. Key components include a web server, a web UI, web sockets, a database, a security repository, and a blockchain implementation.

Explorer 组件为超级账本项目提供了区块链浏览器，可以为基于授权的区块链项目内部的每个成员提供服务。数据的可视化包括：区块，交易，网络状态，智能合约的等各个方面。

Hyperledger Composer

Hyperledger Composer provides a suite of tools for building blockchain business networks. These tools allow you to:

• • Model your business blockchain network
  • Generate REST APIs for interacting with your blockchain network
  • Generate a skeleton Angular application.

Built in Javascript, Hyperledger Composer provides an easy-to-use set of components that developers can quickly learn and implement. The project was contributed by Oxchains and IBM.

Composer 提供了一组用于构建区块链网络的工具，包括对具体应用的建模，供区块链网络通信的REST-API，以及生成基于Angular的应用框架。

####Hyperledger Composer (Simon Stone & Kathryn Harrison)

Hyperledge Composer 介绍

1. So, Hyperledger Composer includes a set of components that will be familiar to a wide range of Javascript developers,
2. whether you are a frontend developer, working on UIs, or a backend developer working on service or code.
3. And these components should make it really familiar and easy for Javascript developers to get going building blockchain applications.
4. We’ve got a data modeling language, that allows you to quickly describe your blockchain business network.
5. You can implement your business logic using standard Javascript code.
6. We have a web-based playground for learning the concepts of Composer, trying it out, testing it,
7. looking at our set of sample business networks and extending them,
8. we have some client libraries for building Javascript applications, editor plugins for your favorite editor, whether it’s Atom or Visual Studio Code,
9. we have some command line utilities for your administrative system, to create scripts to automate tasks within the blockchain.
10. We can also generate skeleton applications.
11. So, once you have taken the time to model your blockchain business network, model the assets and participants,
12. in a couple of minutes, we can generate a UI application for you.
13. All you have to do is run one command, answer a set of simple questions,
14. and then you have a fully functional UI app that you can start tailoring to your user experience.
15. And finally, we are big on APIs.
16. We really want to make it easy to expose your blockchain applications via RESTful APIs that you can use in your client applications, or for integrating with your existing systems.
17. And so, again, we provide a simple command, you run it, you connect it to your blockchain business network, and out pops this REST API that you can start building against.
18. Hyperledger Composer is a developer tool that makes it very easy to create applications on blockchain.
19. If you think about the blockchain world, you have multiple organizations that need to come together and agree on what types of participants, assets, and transactions are taking place.
20. And so, Composer allows developers to very quickly and easily model out the key components of their business use case,
21. in a way that both business and technical teams can align around, to create APIs that make developing applications very simple.
22. Not only does it make it easy to create applications for blockchain,
23. but it also makes frontend and full stack developers that have Javascript skills into blockchain developers.

Composer组件为了解js的开发者提供了一个便捷的开发工具，无论是前端应用开发，还是后台的开发，都可以方便的用Composer组件进行基于超级账本的应用开发。其还提供了一种数据建模语言方便开发者快速的描述特定的业务逻辑。

Hyperledger Composer (Continued)

Hyperledger Composer has created a modelling language that allows you to define the assets, participants, and transactions that make up your business network using business vocabulary. In addition, the transaction logic is then written by developers using Javascript. This simple interface allows business people and technologists to work together on defining their business network.

The benefits of Hyperledger Composer are:

• • Faster creation of blockchain applications, eliminating the massive effort required to build blockchain applications from scratch
  • Reduced risk with well-tested, efficient design that aligns understanding across business and technical analysts
  • Greater flexibility as the higher-level abstractions make it far simpler to iterate.

You can watch an introduction to Hyperledger Composer here.

Composer组件创建了一种模型化语言，其允许开发者用贴近具体业务的描述语句来定义区块链应用中的资产，参与方，交易等元素。交易逻辑则是用JS来实现。整体而言，对于刚接触区块链的开发者或业务人员而言，Composer提供了更便利的应用区块链技术的工具。

A Key Feature of Hyperledger Fabric, Hyperledger Sawtooth, and Hyperledger Iroha

Fabric,Sawtooth,Iroha框架各自的主要特点

1. Could you highlight a key feature for each of the three Hyperledger frameworks: Hyperledger Fabric, Sawtooth, and Iroha?
2. So, Fabric, is one of the most mature technology projects in Hyperledger.
3. It was the first to hit a 1.0 release, and that release, the architecture, the version 1 architecture reflects a tremendous amount of trial, proof of concept and pilot trial, of Fabric,
4. with a lot of different companies out there.
5. And they discovered things like, for scalability reasons, you wanted to separate out the ordering service into a separate set of nodes.
6. Or, you might want to be able to support subsets of exchanges, so that is why there is a feature called private channels, right?
7. And so, those are some of the distinctive parts of Fabric.
8. For Sawtooth, there is a number of distinctive features, but the two that stand out are a consensus mechanism called Proof of Elapsed Time,
9. which takes advantage of some special features on Intel’s chips, and then, an approach to smart contracts called transaction families,
10. where you essentially predefine a set of acceptable templates for smart contracts that, then, the rest of the network can use.
11. And that is a safer approach to doing smart contracts than a fully programmable, general purpose programming language.
12. Finally, Iroha, Hyperledger Iroha, the really distinctive thing about that is it’s written in C++, it’s very tiny and tightly coded,
13. and it’s got a terrific set of mobile libraries, as well.
14. These are all slight differences.
15. Our hope is that, over time, as the projects evolve and mature, and all of them get to a 1.0,
16. that we find ways to bring them even closer together, and make them more compatible and modular and find ways for them to work with each other.

1. Fabric: 目前最成熟的项目，特点一是各个功能插件化，便于开发者按照需求定制；特点二是基于信道的技术，让不同业务的参与方之间的交互相对隔离，提高了区块链上业务传送的安全性。
2. Sawtooth：主要特点有二。特点一是基于PoET的共识机制，利用了Intel芯片的特性；特点二是利用了一种叫做 transaction families的智能合约处理方法，该方法较普适性的程序语言安全性更高。
3. Iroha: 用C++实现的框架，其代码结构短小紧凑，是一个面向移动端应用的框架。

Interoperability between Hyperledger Frameworks

不同框架之间的交互与协作

What do you think will help foster interoperability between these three different Hyperledger frameworks?

So, there’s a number of things that we can do to assist in the interoperability between the different projects at Hyperledger.

One thing we’re working on is kind of an overall architectural view of all the different projects, right?

What are the technologies that sit at kind of the DLT layer, at the smart contract layer, where does identity sit in, right?

And then, we can start to look at these projects and go, “Okay, could we put Fabric down here, could we put Burrow up here?”

Maybe we start to tease apart the distributed ledger part of Fabric from the smart contract part of Fabric, right,

into separate components, so that, when somebody new arrives at the project, or they take a training course like this,

they can start to pick and choose, you know, as building blocks, as appropriate for whatever use case that they want to target, right?

And so, that’s something over time, this kind of modularity approach… Along with that, defining standardized APIs between these different levels, right,

so that we can get to an ideal, where you could pick the Ethereum virtual machine from Burrow, and run that on top of Fabric or on top of Sawtooth,

and, in fact, the Sawtooth and Burrow communities have now actually progressed, and you can now run Ethereum smart contracts on top of Sawtooth, which is pretty cool.

So, I think we’ll see more activity like that.

大概就是说不同的框架将来都会可以利用彼此擅长的部分作为对方的组件共同出现在一个超级账本的应用里。结合上一章节最后的部分，将来各个框架之前的联系会更加的紧密，各个框架间的兼容性和模块化会更优化，最终使得各个框架之前的协同工作会更方便。