區(qū)塊鏈技術(shù)一般用于構(gòu)建交易系統(tǒng)，而且要保證交易的信息真實(shí)可信，可追蹤且不可篡改。每一次交易的信息被確認(rèn)后存儲在一個區(qū)塊中，區(qū)塊信息通過散列技術(shù)加密，以保證信息不被篡改。這些區(qū)塊按時間順序構(gòu)成鏈條。Each node maintains complete blockchain information,and the information of individual nodes is damaged without affecting the blockchain information.This type of information recording method is called distributed ledger.

　　區(qū)塊鏈?zhǔn)且环N特殊的分布式數(shù)據(jù)庫，任何服務(wù)器都可以成為區(qū)塊鏈中的一個節(jié)點(diǎn)，且節(jié)點(diǎn)之間是平等的，無中心化，區(qū)塊鏈中的數(shù)據(jù)是經(jīng)過加密存儲，已經(jīng)存儲的數(shù)據(jù)無法修改，可以保證數(shù)據(jù)的準(zhǔn)確性。

　　

　　/// dev This emits when ownership of any NFT changes by any mechanism.

　　///This event emits when NFTs are created(`from`==0)and destroyed

　　///(`to`==0).Exception:during contract creation,any number of NFTs

　　///may be created and assigned without emitting Transfer.At the time of

　　///any transfer,the approved address for that NFT(if any)is reset to none.

　　event Transfer(address indexed _from,address indexed _to,uint256 indexed _tokenId);

　　/// dev This emits when the approved address for an NFT is changed or

　　///reaffirmed.The zero address indicates there is no approved address.

　　///When a Transfer event emits,this also indicates that the approved

　　///address for that NFT(if any)is reset to none.

　　event Approval(address indexed _owner,address indexed _approved,uint256 indexed _tokenId);

　　/// dev This emits when an operator is enabled or disabled for an owner.

　　///The operator can manage all NFTs of the owner.

　　event ApprovalForAll(address indexed _owner,address indexed _operator,bool _approved);

　　/// notice Count all NFTs assigned to an owner

　　/// dev NFTs assigned to the zero address are considered invalid,and this

　　///function throws for queries about the zero address.

　　/// param _owner An address for whom to query the balance

　　/// return The number of NFTs owned by`_owner`,possibly zero

　　function balanceOf(address _owner)external view returns(uint256);

　　/// notice Find the owner of an NFT

　　/// dev NFTs assigned to zero address are considered invalid,and queries

　　///about them do throw.

　　/// param _tokenId The identifier for an NFT

　　/// return The address of the owner of the NFT

　　function ownerOf(uint256 _tokenId)external view returns(address);

　　/// notice Transfers the ownership of an NFT from one address to another address

　　/// dev Throws unless`msg.sender`is the current owner,an authorized

　　///operator,or the approved address for this NFT.Throws if`_from`is

　　///not the current owner.Throws if`_to`is the zero address.Throws if

　　///`_tokenId`is not a valid NFT.When transfer is complete,this function

　　///checks if`_to`is a smart contract(code size>0).If so,it calls

　　///`onERC721Received`on`_to`and throws if the return value is not

　　///`bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`.

　　/// param _from The current owner of the NFT

　　/// param _to The new owner

　　/// param _tokenId The NFT to transfer

　　/// param data Additional data with no specified format,sent in call to`_to`

　　function safeTransferFrom(address _from,address _to,uint256 _tokenId,bytes calldata data)external payable;

　　/// notice Transfers the ownership of an NFT from one address to another address

　　/// dev This works identically to the other function with an extra data parameter,

　　///except this function just sets data to"".

　　/// param _from The current owner of the NFT

　　/// param _to The new owner

　　/// param _tokenId The NFT to transfer

　　function safeTransferFrom(address _from,address _to,uint256 _tokenId)external payable;

　　/// notice Transfer ownership of an NFT--THE CALLER IS RESPONSIBLE

　　///TO CONFIRM THAT`_to`IS CAPABLE OF RECEIVING NFTS OR ELSE

　　///THEY MAY BE PERMANENTLY LOST

　　/// dev Throws unless`msg.sender`is the current owner,an authorized

　　///operator,or the approved address for this NFT.Throws if`_from`is

　　///not the current owner.Throws if`_to`is the zero address.Throws if

　　///`_tokenId`is not a valid NFT.

　　/// param _from The current owner of the NFT

　　/// param _to The new owner

　　/// param _tokenId The NFT to transfer

　　function transferFrom(address _from,address _to,uint256 _tokenId)external payable;

　　/// notice Change or reaffirm the approved address for an NFT

　　/// dev The zero address indicates there is no approved address.

　　///Throws unless`msg.sender`is the current NFT owner,or an authorized

　　///operator of the current owner.

　　/// param _approved The new approved NFT controller

　　/// param _tokenId The NFT to approve

　　function approve(address _approved,uint256 _tokenId)external payable;

　　/// notice Enable or disable approval for a third party("operator")to manage

　　///all of`msg.sender`'s assets

　　/// dev Emits the ApprovalForAll event.The contract MUST allow

　　///multiple operators per owner.

　　/// param _operator Address to add to the set of authorized operators

　　/// param _approved True if the operator is approved,false to revoke approval

　　function setApprovalForAll(address _operator,bool _approved)external;

　　/// notice Get the approved address for a single NFT

　　/// dev Throws if`_tokenId`is not a valid NFT.

　　/// param _tokenId The NFT to find the approved address for

　　/// return The approved address for this NFT,or the zero address if there is none

　　function getApproved(uint256 _tokenId)external view returns(address);

　　/// notice Query if an address is an authorized operator for another address

　　/// param _owner The address that owns the NFTs

　　/// param _operator The address that acts on behalf of the owner

　　/// return True if`_operator`is an approved operator for`_owner`,false otherwise

　　function isApprovedForAll(address _owner,address _operator)external view returns(bool);

　　}