Blockchain metadata
Trials volume 18 , Article number: Cite this article. Metrics details. Reproducibility, data sharing, personal data privacy concerns and patient enrolment in clinical trials are huge medical challenges for contemporary clinical research. A new technology, Blockchain, may be a key to addressing these challenges and should draw the attention of the whole clinical research community. Blockchain brings the Internet to its definitive decentralisation goal.
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Content:
- Adding Metadata to the Blockchain, part 1
- Trade secret metadata and blockchain evidence: a perfect combination
- Azure Blockchain Workbench configuration reference
- Banking Is Only The Beginning: 58 Big Industries Blockchain Could Transform
- How Blockchain Can Help Combat Disinformation
- We apologize for the inconvenience...
- New Report: What use is Blockchain for journalism?
- blockchain database, cata metadata query
Adding Metadata to the Blockchain, part 1
The blockchain data structure is an ordered, back-linked list of blocks of transactions. The blockchain can be stored as a flat file, or in a simple database. Blocks are linked "back," each referring to the previous block in the chain. The blockchain is often visualized as a vertical stack, with blocks layered on top of each other and the first block serving as the foundation of the stack.
The visualization of blocks stacked on top of each other results in the use of terms such as "height" to refer to the distance from the first block, and "top" or "tip" to refer to the most recently added block. Each block within the blockchain is identified by a hash, generated using the SHA cryptographic hash algorithm on the header of the block.
Each block also references a previous block, known as the parent block, through the "previous block hash" field in the block header. In other words, each block contains the hash of its parent inside its own header. The sequence of hashes linking each block to its parent creates a chain going back all the way to the first block ever created, known as the genesis block.
Although a block has just one parent, it can temporarily have multiple children. Each of the children refers to the same block as its parent and contains the same parent hash in the "previous block hash" field. Multiple children arise during a blockchain "fork," a temporary situation that occurs when different blocks are discovered almost simultaneously by different miners see [forks].
Eventually, only one child block becomes part of the blockchain and the "fork" is resolved. Even though a block may have more than one child, each block can have only one parent.
This is because a block has one single "previous block hash" field referencing its single parent. This cascade effect ensures that once a block has many generations following it, it cannot be changed without forcing a recalculation of all subsequent blocks.
One way to think about the blockchain is like layers in a geological formation, or glacier core sample. The surface layers might change with the seasons, or even be blown away before they have time to settle. But once you go a few inches deep, geological layers become more and more stable. By the time you look a few hundred feet down, you are looking at a snapshot of the past that has remained undisturbed for millions of years.
In the blockchain, the most recent few blocks might be revised if there is a chain recalculation due to a fork. The top six blocks are like a few inches of topsoil. But once you go more deeply into the blockchain, beyond six blocks, blocks are less and less likely to change. After blocks back, there is so much stability that the coinbase transaction—the transaction containing newly mined bitcoin—can be spent.
A few thousand blocks back a month and the blockchain is settled history, for all practical purposes. While the protocol always allows a chain to be undone by a longer chain and while the possibility of any block being reversed always exists, the probability of such an event decreases as time passes until it becomes infinitesimal. A block is a container data structure that aggregates transactions for inclusion in the public ledger, the blockchain.
The block is made of a header, containing metadata, followed by a long list of transactions that make up the bulk of its size. The block header is 80 bytes, whereas the average transaction is at least bytes and the average block contains more than transactions. A complete block, with all transactions, is therefore 10, times larger than the block header.
The structure of a block describes the structure of a block. The block header consists of three sets of block metadata. First, there is a reference to a previous block hash, which connects this block to the previous block in the blockchain. The second set of metadata, namely the difficulty , timestamp , and nonce , relate to the mining competition, as detailed in [mining]. The third piece of metadata is the merkle tree root, a data structure used to efficiently summarize all the transactions in the block.
The structure of the block header describes the structure of a block header. The nonce, difficulty target, and timestamp are used in the mining process and will be discussed in more detail in [mining]. The primary identifier of a block is its cryptographic hash, a digital fingerprint, made by hashing the block header twice through the SHA algorithm. The resulting byte hash is called the block hash but is more accurately the block header hash , because only the block header is used to compute it.
For example, dcaeeffae46a2a6cb3f1b60a8ce26f is the block hash of the first bitcoin block ever created. The block hash identifies a block uniquely and unambiguously and can be independently derived by any node by simply hashing the block header. A second way to identify a block is by its position in the blockchain, called the block height.
The first block ever created is at block height 0 zero and is the same block that was previously referenced by the following block hash dcaeeffae46a2a6cb3f1b60a8ce26f. A block can thus be identified in two ways: by referencing the block hash or by referencing the block height. Each subsequent block added "on top" of that first block is one position "higher" in the blockchain, like boxes stacked one on top of the other.
The block height on January 1, was approximately ,, meaning there were , blocks stacked on top of the first block created in January Unlike the block hash, the block height is not a unique identifier. Although a single block will always have a specific and invariant block height, the reverse is not true—the block height does not always identify a single block. Two or more blocks might have the same block height, competing for the same position in the blockchain.
This scenario is discussed in detail in the section [forks]. The block height might also be stored as metadata in an indexed database table for faster retrieval. A block also always has a specific block height. However, it is not always the case that a specific block height can identify a single block.
Rather, two or more blocks might compete for a single position in the blockchain. The first block in the blockchain is called the genesis block and was created in It is the common ancestor of all the blocks in the blockchain, meaning that if you start at any block and follow the chain backward in time, you will eventually arrive at the genesis block.
Every node always starts with a blockchain of at least one block because the genesis block is statically encoded within the bitcoin client software, such that it cannot be altered. Thus, every node has the starting point for the blockchain, a secure "root" from which to build a trusted blockchain. See the statically encoded genesis block inside the Bitcoin Core client, in chainparams.
You can search for that block hash in any block explorer website, such as blockchain. The genesis block contains a hidden message within it. Bitcoin full nodes maintain a local copy of the blockchain, starting at the genesis block. The local copy of the blockchain is constantly updated as new blocks are found and used to extend the chain.
As a node receives incoming blocks from the network, it will validate these blocks and then link them to the existing blockchain. To establish a link, a node will examine the incoming block header and look for the "previous block hash. The last block the node knows about is block ,, with a block header hash of:. Looking at this new block, the node finds the previousblockhash field, which contains the hash of its parent block. It is a hash known to the node, that of the last block on the chain at height , Therefore, this new block is a child of the last block on the chain and extends the existing blockchain.
The node adds this new block to the end of the chain, making the blockchain longer with a new height of , Blocks linked in a chain by reference to the previous block header hash shows the chain of three blocks, linked by references in the previousblockhash field. Each block in the bitcoin blockchain contains a summary of all the transactions in the block using a merkle tree. A merkle tree , also known as a binary hash tree , is a data structure used for efficiently summarizing and verifying the integrity of large sets of data.
Merkle trees are binary trees containing cryptographic hashes. The term "tree" is used in computer science to describe a branching data structure, but these trees are usually displayed upside down with the "root" at the top and the "leaves" at the bottom of a diagram, as you will see in the examples that follow.
Merkle trees are used in bitcoin to summarize all the transactions in a block, producing an overall digital fingerprint of the entire set of transactions, providing a very efficient process to verify whether a transaction is included in a block. A merkle tree is constructed by recursively hashing pairs of nodes until there is only one hash, called the root , or merkle root.
The merkle tree is constructed bottom-up. In the following example, we start with four transactions, A, B, C, and D, which form the leaves of the merkle tree, as shown in Calculating the nodes in a merkle tree. The transactions are not stored in the merkle tree; rather, their data is hashed and the resulting hash is stored in each leaf node as H A , H B , H C , and H D :. Consecutive pairs of leaf nodes are then summarized in a parent node, by concatenating the two hashes and hashing them together.
For example, to construct the parent node H AB , the two byte hashes of the children are concatenated to create a byte string. The process continues until there is only one node at the top, the node known as the merkle root. That byte hash is stored in the block header and summarizes all the data in all four transactions.
Calculating the nodes in a merkle tree shows how the root is calculated by pair-wise hashes of the nodes. Because the merkle tree is a binary tree, it needs an even number of leaf nodes. If there is an odd number of transactions to summarize, the last transaction hash will be duplicated to create an even number of leaf nodes, also known as a balanced tree. This is shown in Duplicating one data element achieves an even number of data elements , where transaction C is duplicated.
The same method for constructing a tree from four transactions can be generalized to construct trees of any size. In bitcoin it is common to have several hundred to more than a thousand transactions in a single block, which are summarized in exactly the same way, producing just 32 bytes of data as the single merkle root.
In A merkle tree summarizing many data elements , you will see a tree built from 16 transactions. Note that although the root looks bigger than the leaf nodes in the diagram, it is the exact same size, just 32 bytes. Whether there is one transaction or a hundred thousand transactions in the block, the merkle root always summarizes them into 32 bytes. This is especially important as the number of transactions increases, because the base-2 logarithm of the number of transactions increases much more slowly.
This allows bitcoin nodes to efficiently produce paths of 10 or 12 hashes — bytes , which can provide proof of a single transaction out of more than a thousand transactions in a megabyte-sized block.
In A merkle path used to prove inclusion of a data element , a node can prove that a transaction K is included in the block by producing a merkle path that is only four byte hashes long bytes total.
The code in Building a merkle tree demonstrates the process of creating a merkle tree from the leaf-node hashes up to the root, using the libbitcoin library for some helper functions. Compiling and running the merkle example code shows the result of compiling and running the merkle code. The efficiency of merkle trees becomes obvious as the scale increases.
Trade secret metadata and blockchain evidence: a perfect combination
Since an NFT can't be easily changed after it's been created, it's a good idea to think about how the data for your NFTs is stored, addressed, and made persistent over time. That's why we'll be getting into the specifics of how to prepare your NFT metadata , and we'll also look at the different kinds of links to IPFS content and when you should use each one. Finally, we'll see why making a plan for your data's persistence is important for a good user experience. By following these recommendations, you can help ensure a long and healthy future for your NFT data.
Azure Blockchain Workbench configuration reference
A ledger is a key concept in Hyperledger Fabric; it stores important factual information about business objects; both the current value of the attributes of the objects, and the history of transactions that resulted in these current values. A ledger contains the current state of a business as a journal of transactions. If you want to see how your balance was derived, then you can look through the transaction credits and debits that determined it. This is a real life example of a ledger — a state your bank balance , and a set of ordered transactions credits and debits that determine it. Hyperledger Fabric is motivated by these same two concerns — to present the current value of a set of ledger states, and to capture the history of the transactions that determined these states. While the facts about the current state of a business object may change, the history of facts about it is immutable , it can be added to, but it cannot be retrospectively changed. In Hyperledger Fabric, a ledger consists of two distinct, though related, parts — a world state and a blockchain. Each of these represents a set of facts about a set of business objects. The world state makes it easy for a program to directly access the current value of a state rather than having to calculate it by traversing the entire transaction log. The world state can change frequently, as states can be created, updated and deleted.
Banking Is Only The Beginning: 58 Big Industries Blockchain Could Transform
Welcome to Reuters Legal News beta. Please enjoy and provide us with your feedback as we continue to improve the Reuters Legal News experience. Representations of cryptocurrencies Bitcoin and Ethereum are placed on PC motherboard in this illustration taken, June 29, The company and law firm names shown above are generated automatically based on the text of the article. We are improving this feature as we continue to test and develop in beta.
How Blockchain Can Help Combat Disinformation
Any data file stored on IPFS can be easily accessed from Drill's query interface, just like a file stored on a local disk. Moreover, with Drill's capability of distributed execution, other instances who are also running Minerva can help accelerate the execution: the data stays where it was, and the queries go to the most suitable nodes which stores the data locally and from there the operations can be performed most efficiently. Note that it's still in early stages of development and the overall stability and performance is not satisfactory. PRs are very much welcome! Drill 1.
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JAAK, like others in the field IBM, Dot Blockchain and Blokur are just a few , aims to use the tech to build a comprehensive decentralized IP database that will solve many of the inconsistencies, omissions and errors that currently litter the music rights landscape. The missed opportunity of having lots of different types of music experiences is the real cost. McKenzie-Landell is confident that using blockchain tech is a big part of the solution. Other participants in the music-focused pilot include Beijing-based consultancy Outdustry, independent publisher Sentric and Phoenix Music International, who all provided product and rights data to JAAK, which were then fed into a private version of its blockchain network KORD. From there, JAAK was able to identify any conflicts in the rights data, for example royalty splits, enabling rights owners to collaborate and hopefully come to a resolution. Although still early days, the pilot, which launched in September, has been hailed a success by its partner members. The large number of rival companies using blockchain tech to achieve the same goal can only be a good thing, says the CEO. Daily newsletters straight to your inbox.
New Report: What use is Blockchain for journalism?
Skip to search form Skip to main content Skip to account menu You are currently offline. Some features of the site may not work correctly. These data cannot be processed by the traditional database systems. Hadoop is a distributed and massively parallel processing system for big data whereby the storage is based on the distributed file system called HadoopDistributed File System HDFS.
blockchain database, cata metadata query
RELATED VIDEO: Set up an ScPrime Storage Provider on Windows for Passive IncomeJanuary 31, 5 min read The non-fungible token NFT industry has grown at a rapid pace in the past few years. It began as a crazy idea, but then all of a sudden, boom! It became the next big thing. People were still processing the idea behind blockchain, but now, the industry is finally ready to take the blockchain to the next level. The figures are maddening, especially for such a brand new art form.
Blockchains will create immense amounts of immutable data—and how that data is stored can make or break the success of blockchain-based apps. Carey Wodehouse. Carey Wodehouse is a tech content writer based in Richmond, VA. This is part two in a three-part series covering blockchain technologies. Read part one to learn how blockchain is modernizing enterprise apps.
This is a guest post from the. Hello we are the. Your experience on the Flow Blockchain is about to get even better. It was founded by Bjartek, who many of you will know from all over the Flow community.
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