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Introduction

Those having experience in developing chaincode in Fabric know well how a chaincode looks like. In a nutshell, we define the data structure (state) for some assets, and functions which one can query the state, or invoke if change of state is needed. Since v2.1, Fabric team also introduces Contract API (link) which simplifies the way chaincode is written. This still follows the same pattern.

Recently I see another attempt to change the way we develop smart contracts with classes and objects, which is a favourite model for many developers. Prasaga introduces Extensible Blockchain Object Model, XBOM, in which assets are defined as objects and owned by accounts. XBOM provides a coding environment and methodology, which is currently implemented in Hyperledger Fabric for a permissioned chain offering and will be available on DataGrid Blockchain (DGB), an open permissionless chain in the future. …


Introduction

In my previous work several important concepts like template, contract and transaction about DAML were introduced, with a very simple IOU demonstrating the relationship between them. We have seen how a new contract instance of the same template is created through choices. Here we make it more interesting and realistic: how two contracts are interacting with each other in DAML through choices.

DAML tutorial 6 gives us a good example, which is good for extending our previous IOU example. As it is needed to make owner as signatory (in addition to issuer), the transfer of IOU now is implemented as proposal-acceptance model, which means that one party proposes a transfer, and the other party can accept or reject it. …


Introduction

Early this July my article System Channel and Application Channel was about a tutorial “Adding an Org to a Channel” (link), driven by a question from my readers. I received another question this week which again led me to revisit this topic. The question was about modifying a batch timeout (amount of time to wait before creating a block) in Hyperledger Fabric. While it is quite clear that we can update configuration through the standard (and tedious) process, what puzzled me at the beginning is which channel I should work on: system channel or application channel.

My very first guess is that, as blocks are created in an orderer, the configuration update should be made on the system (orderer) channel, and then the orderer will honour this new timeout for all channels. After some experiments my guess is wrong! (Always learn new things in each hands-on practice.) …

About

KC Tam

Happy to share what I learn on blockchain. Visit http://www.ledgertech.biz/kcarticles.html for my works. or reach me on https://www.linkedin.com/in/ktam1/.

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