BIM-chain

Blockchain & Tokens

TBD

• Property token
• Possession token

Data layer exercises

The following is a short excercise on how to put data onto ipfs and retrieve it again. The idea is to put the reference (ipfs hash) to this data somewhere onto the blockchain and given that reference, retrieve the data from anywhere.

Precondition (installation instructions for ubuntu):

• ipfs (data layer technology) installed & running. sudo snap install ipfs && ipfs init && ipfs daemon
• jq (data extraction tool for JSON) installed. sudo apt install jq

prepare, publish data & save reference hash

split 5 objects and save the first in data.json

1. jq '.[0]' test/mocks/5objects.json > data.json

add the data to ipfs, which returns a hash to retrieve the data from the network later, (which we will save in a database/blockchain)

2. ipfs add data.json

save the reference that was output (Qme... is the format of your ipfs hash)

3. echo Qme5GawkhEceihJYYccGPvK5MzatwcAifa85qhNmMowcb2 > ref

prepare, publish data & save reference hash (alternative command)

Alternatively you can do 1, 2 & 3 in 1 command like this:

1. jq '.[0]' test/mocks/5objects.json | ipfs add - | awk '{ print $NF }' > ref

fetch data & extract a value

get the data from data layer back, e.g. cpi property

1. ipfs cat `cat ref` | jq '.cpi'

download data from ipfs

ipfs deamon
ipfs cat Qme5GawkhEceihJYYccGPvK5MzatwcAifa85qhNmMowcb2 > data/block1.json