Querying ActivityPub collections

I don’t know the applicability of this, but just wanted to mention the Meld protocol here (project will be presenting at @j8ter NGI Linked Data webinar at 9.30 CEST).

At the heart of m-ld is a decentralised protocol for distributing live state among clones . Using m-ld , every app instance has read-write access to the shared information via its local clone, with zero network latency. Changes to the information are propagated to all other app instances, so they are all eventually consistent .

The specification includes a query language json-rql that is is a superset of JSON-LD, designed for query expressions.

  1. It’s JSON: straightforward to construct in code, manipulate and serialize, and also to constrain . Use standard JSON tooling such as JSON schema to limit your API to the queries that your back-end has been designed and tested for.
  2. It’s SPARQL: in context , all queries can be translated to the W3C standard language for directed, labeled graph data. This means that your API can be extended to cover future query requirements, without breaking changes.

With Meld, apps use one of available Message-layer adapters to synchronise clones of ‘domain’ data. It seems like this layer may as well be an ActivityPub adapter. A Java platform implementation is apparently in the works.

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