[FAB-3830] Why Blockchain

High level concept view of blockchain
to start the story, hope to move to HL umbrella later
Adding 3 new images too for doc
slight change to wording
added why BC and temp images
added What is Hyperledger Fabric section and learn more
Edit updates
rebased on master

Change-Id: I76ceb47fc5403ae35f30bd0ee97044ae12227ccf
Signed-off-by: Mark Parzygnat <[email protected]>
Signed-off-by: Christopher Ferris <[email protected]>

Author: ibmmark

docs/source/blockchain.rst

@@ -1,4 +1,272 @@
-Why blockchain?
-===============
+Introduction
+============
+This section provides an introduction to blockchain that will allow you to
+quickly determine whether it might be useful for you or your business. It also
+explains the characteristics of the Hyperledger Fabric blockchain and suggests
+some ways to increase your knowledge and understanding.
 
-...coming soon
+What is a Blockchain?
+---------------------
+**A Distributed Ledger**
+
+At the heart of a blockchain network is a distributed ledger that records all
+the transactions that take place on the network.
+
+A blockchain ledger is often described as **decentralized** because it is replicated
+across many network participants, each of whom **collaborate** in its maintenance.
+We’ll see that decentralization and collaboration are powerful attributes that
+mirror the way businesses exchange goods and services in the real world.
+
+.. image:: images/basic_network.png
+
+In addition to being decentralized and collaborative, the information recorded
+to a blockchain is append-only, using cryptographic techniques that guarantee
+that once a transaction has been added
+to the ledger it cannot be modified. This property of immutability makes it
+simple to determine the provenance of information because participants can be
+sure information has not been changed after the fact. It’s why blockchains
+are sometimes described as **systems of proof**.
+
+ 
+**Smart Contracts**
+
+To support the consistent update of information – and to enable a whole host of
+ledger functions (transacting, querying, etc) – a blockchain network uses **smart
+contracts** to provide controlled access to the ledger.
+
+.. image:: images/Smart_Contract.png
+
+Smart contracts are not only a key mechanism for encapsulating information
+and keeping it simple across the network, they can also be written to allow
+participants to execute certain aspects of transactions automatically.
+
+A smart contract can, for example, be written to stipulate the cost of shipping
+an item that changes depending on when it arrives. With the terms agreed to
+by both parties and written to the ledger, the appropriate funds change hands
+automatically when the item is received.
+
+**Consensus**
+
+The process of keeping the ledger transactions synchronized across the network –
+to ensure that ledgers only update when transactions are approved by the appropriate
+participants, and that when ledgers do update, they update with the
+same transactions in the same order – is called **consensus**.
+
+.. image:: images/consensus.png
+
+We’ll learn a lot more about ledgers, smart contracts and consensus later. For
+now, it’s enough to think of a blockchain as a shared, replicated transaction
+system which is updated via smart contracts and kept consistently
+synchronized through a collaborative process called consensus.
+
+Why is a Blockchain useful?
+---------------------------
+
+**Today’s Systems of Record**
+
+The transactional networks of today are little more than slightly updated
+versions of networks that have existed since business records have been kept.
+The members of a **Business Network** transact with each other, but they maintain
+separate records of their transactions. And the things they’re transacting –
+whether it’s Flemish tapestries in the 16th century or the securities of today
+– must have their provenance established each time they’re sold to ensure that
+the business selling an item possesses a chain of title verifying their
+ownership of it.
+
+What you’re left with is a business network that looks like this:
+
+
+.. image:: images/current_network.png
+
+Modern technology has taken this process from stone tablets and paper folders
+to hard drives and cloud platforms, but the underlying structure is the same.
+Unified systems for managing the identity of network participants do not exist,
+establishing provenance is so laborious it takes days to clear securities
+transactions (the world volume of which is numbered in the many trillions of
+dollars), contracts must be signed and executed manually, and every database in
+the system contains unique information and therefore represents a single point
+of failure.
+
+It’s impossible with today’s fractured approach to information and
+process sharing to build a system of record that spans a business network, even
+though the needs of visibility and trust are clear.
+
+
+**The Blockchain Difference**
+
+What if instead of the rat’s nest of inefficiencies represented by the “modern”
+system of transactions, business networks had standard methods for establishing
+identity on the network, executing transactions, and storing data? What
+if establishing the provenance of an asset could be determined by looking
+through a list of transactions that, once written, cannot be changed, and can
+therefore be trusted?
+
+That business network would look more like this:
+
+.. image:: images/future_net.png
+
+This is a blockchain network. Every participant in it has their own replicated
+copy of the ledger. In addition to ledger information being shared, the processes
+which update the ledger are also shared. Unlike today’s systems, where a
+participant’s **private** programs are used to update their **private** ledgers,
+a blockchain system has **shared** programs to update **shared** ledgers.
+
+With the ability to coordinate their business network through a shared ledger,
+blockchain networks can reduce the time, cost, and risk associated with private information and
+processing while improving trust and visibility.
+
+You now know what blockchain is and why it’s useful. There are a lot of other
+details that are important, but they all relate to these fundamental ideas of
+the sharing of information and processes.
+
+
+What is Hyperledger Fabric?
+---------------------------
+
+The Linux Foundation founded the Hyperledger Project in 2015 to advance
+cross-industry blockchain technologies. Rather than declaring a single
+blockchain standard, it encourages a collaborative approach to developing
+blockchain technologies via a community process, with intellectual property
+rights that encourage open development and the adoption of key standards over
+time.
+
+Hyperledger Fabric is a one of the blockchain projects within Hyperledger.
+Like other blockchain technologies, it has a ledger, uses smart contracts,
+and is a system by which participants manage their transactions.
+
+Where Hyperledger Fabric breaks from some other blockchain systems is that
+it is **private** and **permissioned**. Rather than the “proof of work” some 
+blockchain networks use to verify identity (allowing anyone who meets those 
+criteria to join the network), the members of a Fabric network enroll through 
+a **membership services provider**.
+
+Fabric also offers several pluggable options. Ledger data can be stored in
+multiple formats, consensus mechanisms can be switched in and out,
+and different membership service providers are supported.
+
+Fabric also offers the ability to create **channels**, allowing a group of
+participants to create a separate ledger of transactions. This is an especially
+important option for networks where some participants might be competitors and not
+want every transaction they make - a special price they're offering to some participants
+and not others, for example - known to every participant. If two
+participants form a channel, then those participants – and no others – have copies
+of the ledger for that channel.
+
+The following diagram outlines the four building blocks of Hyperledger Fabric:
+
+.. image:: images/Requirements.png
+
+**Shared Ledger**
+
+Hyperledger Fabric has a ledger subsystem comprising two components: the **world
+state** and the **transaction log**. Each participant has a copy of the ledger to
+every Fabric network they belong to.
+
+.. image:: images/what.png
+
+The world state component describes the state of the ledger at a given point
+in time. It’s the database of the ledger. The transaction log component records
+all transactions which have resulted in the current value of the world state.
+It’s the update history for the world state. The ledger, then, is a combination
+of the world state database and the transaction log history.
+
+The ledger has a replaceable data store for the world state. By default, this
+is a LevelDB key-value store database. The transaction log does not need to be
+pluggable. It simply records the before and after values of the ledger database
+being used by the blockchain network.
+
+**Smart Contracts**
+
+Hyperledger Fabric smart contracts are written in **chaincode** and are invoked
+by an application external to the blockchain when that
+application needs to interact with the ledger. In most cases chaincode only
+interacts with the database component of the ledger, the world state (querying
+it, for example), and not the transaction log.
+
+.. image:: images/sContracts.png
+
+You can write chaincode in several programming languages. Currently supported
+languages include GOLANG and Java with others coming soon.
+
+**Privacy**
+
+Depending on the needs of a network, participants in a Business-to-Business
+(B2B) network might be extremely sensitive about how much information they share.
+For other networks, privacy will not be a top concern.
+
+.. image:: images/Lock.png
+
+Hyperledger Fabric supports networks where privacy (using channels) is a key
+operational requirement as well as networks that are comparatively open.
+
+**Consensus**
+
+Transactions must be written to the ledger in the order in which they occur,
+even though they might be between different sets of participants within the
+network. For this to happen, the order of transactions must be established
+and a method for rejecting bad transactions that have been inserted into the
+ledger in error (or maliciously) must be put into place.
+
+.. image:: images/handshake.png
+
+
+This is a thoroughly researched area of computer science, and there are many
+ways to achieve it, each with different trade-offs. For example, PBFT (Practical
+Byzantine Fault Tolerance) can provide a mechanism for file replicas to
+communicate with each other to keep each copy consistent, even in the event
+of corruption. Alternatively, in Bitcoin, ordering happens through a process
+called mining where competing computers race to solve a cryptographic puzzle
+which defines the order that all processes subsequently build upon.
+
+Hyperledger Fabric has been designed to allow network starters to choose a
+consensus mechanism that best represents the relationships that exist between
+participants. As with privacy, there is a spectrum of needs; from networks
+that are highly structured in their relationships to those that are more 
+peer-to-peer.
+
+We’ll learn more about the Hyperledger Fabric consensus mechanisms, which
+currently include SOLO, Kafka, and will soon extend to SBFT (Simplified
+Byzantine Fault Tolerance), in another document.
+
+
+Where can I learn more?
+-----------------------
+
+:doc:`getting_started`
+
+Where you learn how to set up a sample network on your local machine. You’ll be
+introduced to most of the key components within a blockchain network, learn
+more about how they interact with each other, and then you’ll actually get the
+code and run some simple query and update transactions.
+
+:doc:`fabric_model`
+
+A deeper look at the components and concepts brought up in this introduction as
+well as a few others and describes how they work together in a sample
+transaction flow.
+
+:doc:`marbles`
+
+Where you can learn how to write a sample smart contract in GOLANG and invoke
+it from an application written in JavaScript. You’ll become comfortable with
+the key APIs used by both smart contract developers and application developers
+and ready to write your own application using the Hyperledger Fabric API
+reference information.
+
+Designing a Business Network (coming soon)
+
+Takes you through how to design a business network using a standard process.
+You’ll start by defining the business network and identify the participants
+and the goods and services that move between them. You’ll think about the key
+lifecycles and how they are impacted by the activities of the key participants.
+By the time you’re through, you’ll be ready to start working with key
+stakeholders in your company to design a business network that uses Hyperledger
+Fabric.
+
+:doc:`planning_guide`
+
+Deals with the practical concerns of setting up and managing a production
+Hyperledger Fabric blockchain. You’ll understand the key factors to consider
+when planning a blockchain solution, such as compute, storage and network
+requirements. You’ll also understand the key non-functional requirements,
+including maintainability, performance, availability and disaster recovery.

docs/source/images/Smart_Contract.png

@@ -17,7 +17,8 @@ It's recommended for first-time users to begin by going through the
 components and the basic transaction flow.  Once comfortable, continue
 exploring the library for demos, technical specifications, APIs, etc.
 
-Before diving in, watch how Fabric is `Building a Blockchain for Business <https://www.youtube.com/watch?v=EKa5Gh9whgU>`__ .
+Before diving in, watch how Fabric is `Building a Blockchain for Business
+<https://www.youtube.com/watch?v=EKa5Gh9whgU>`__ .
 
 
 
@@ -40,6 +41,7 @@ Before diving in, watch how Fabric is `Building a Blockchain for Business <https
    :caption: Key Concepts
 
    overview
+   blockchain
    capabilities
    fabric_model
    usecases