2017-06-05 12:37:23 +00:00
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The ledger
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==========
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.. topic:: Summary
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* *The ledger is subjective from each peer's perspective*
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* *Two peers are always guaranteed to see the exact same version of any on-ledger facts they share*
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2018-06-13 08:43:16 +00:00
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.. only:: htmlmode
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Video
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-----
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.. raw:: html
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<iframe src="https://player.vimeo.com/video/213812040" width="640" height="360" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen></iframe>
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<p></p>
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2017-06-07 15:14:01 +00:00
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2017-06-05 12:37:23 +00:00
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Overview
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--------
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In Corda, there is **no single central store of data**. Instead, each node maintains a separate database of known
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facts. As a result, each peer only sees a subset of facts on the ledger, and no peer is aware of the ledger in its
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entirety.
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For example, imagine a network with five nodes, where each coloured circle represents a shared fact:
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.. image:: resources/ledger-venn.png
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2017-06-07 15:14:01 +00:00
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:scale: 25%
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:align: center
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2017-06-05 12:37:23 +00:00
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We can see that although Carl, Demi and Ed are aware of shared fact 3, **Alice and Bob are not**.
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Equally importantly, Corda guarantees that whenever one of these facts is shared by multiple nodes on the network, it evolves
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in lockstep in the database of every node that is aware of it:
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.. image:: resources/ledger-table.png
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2017-06-07 15:14:01 +00:00
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:scale: 25%
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:align: center
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2017-06-05 12:37:23 +00:00
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For example, Alice and Bob will both see the **exact same version** of shared facts 1 and 7.
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