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Taking MultiChain streams to a whole new level

Today we’re delighted to share the first preview release of MultiChain 2.0, which implements one major part of the MultiChain 2.0 roadmap published earlier this year – a richer data model for streams.

Streams have proven to be a popular feature in MultiChain, providing a natural abstraction for general purpose data storage and retrieval on a blockchain. A MultiChain chain can contain any number of named streams, each of which can have individual write permissions or be open for writing by all. In MultiChain 1.0, each stream item has one or more publishers (who sign it), an optional key for efficient retrieval, a binary data payload up to 64 MB in size, and a timestamp derived from the block in which it’s embedded.

This preview release of MultiChain 2.0, numbered alpha 1, takes streams functionality to a whole new level:

  • JSON items. As an optional alternative to raw binary data, stream items can now contain any JSON structure, which is stored on the blockchain in the efficient UBJSON serialization format. Since the MultiChain API already uses JSON throughout, these JSON structures can be read and written in a natural and obvious way.
  • Text items. Stream items may also contain Unicode text, stored efficiently on the blockchain in UTF-8 encoding. Text items can also be read and written directly via the MultiChain API.
  • Multiple keys. Each stream item can now have multiple keys instead of only one. This enables much more flexible schemes for tagging, indexing and retrieval.
  • Multiple items per transaction. Multiple items can now be written to the same stream in a single atomic transaction. This allows multiple stream items to: (a) be naturally grouped together under a single transaction ID, (b) take up less space on the blockchain and (c) require fewer signature verifications.
  • JSON merging. There are new APIs to summarize the items in a stream with a particular key or publisher. The first type of summary offered is a merge of all of the JSON objects in those items. The outcome of the merge is a new object containing all the JSON keys from the individual objects, where the value corresponding to each JSON key is taken from the last item in which that key appears. The merge can be customized in various ways, e.g. to control whether sub-objects are merged recursively and if null values should be included.

The purpose of JSON merging is to enable a stream to serve as a flexible database for applications built on MultiChain, with the stream key or publisher (as appropriate) acting as a “primary key” for each database entry. The advantage over a regular database is that the stream contains a fully signed and timestamped history of how each entry was changed over time, with the blockchain securing this history immutably through multiparty consensus.

As in previous versions, each node can freely decide which streams to subscribe to, or can subscribe to all streams automatically. If a node is subscribed to a stream, it indexes that stream’s content in real time, allowing efficient retrieval by publisher, key, block, timestamp or position – and now summarization by key or publisher.

Aside from stream items, MultiChain 2.0 alpha 1 also supports JSON and text in raw transaction metadata, as alternatives to the raw binary data supported in MultiChain 1.0.

Finally, this release allows the custom fields of issued assets and created streams to contain any JSON object, instead of the text-only key/value pairs offered in MultiChain 1.0. For forwards compatibility, MultiChain 1.0.2 includes the ability to read (but not write) these richer asset and stream custom fields.

To try out these new features, visit the MultiChain 2.0 preview releases page and download alpha 1. The page also provides detailed documentation on the new APIs and parameters available.

We’d love to hear your feedback on this new functionality. And of course we’re already hard at work on the next major set of enhancements for MultiChain 2.0, scheduled for release early next year.


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