Automatic Tag Propagation Policies and Forwarding Policy Updates

[drslebedev]

This is a follow-up issue to #407.

Automatic Tag Propagation Policy

• Relevant only for blocks with `non-N_in=1:M_out=1' chunked data constraints.
• Introduce an optional block attribute (similar to Resampling or BlockingIO) to define tag propagation policies.
• Proposed policies:
  • Forward-propagate (default): Treat the tag as if it belongs to the first sample of the next processBulk(..) invocation.
  • Backward-propagate: Treat the tag as if it belongs to the first sample of the current processBulk(..) invocation.
  • Ignore: Tag propagation must be handled manually by the user within the processBulk(..) function (see Forwarding Policy below).
  • Action Items:
    • Implement proposed above Automatic Tag Propagation Policy

Forwarding Policy

• Currently, we have all-to-all and one-to-one strategies defined, but only the all-to-all strategy is implemented.
• (The idea of providing a customization point for users to plug in predefined or custom strategies has been abandoned.)
• Instead, tag forwarding should be managed within the custom processBulk(..) function using the new InputSpan and OutputSpan API.
• Action Items:
  • Implement a way to suppress automatic tag forwarding.
  • Modify the existing Selector block to demonstrate how to explicitly forward the correct tags to the appropriate output samples.

Related issues

• Tags forwarding when some ports are not connected or Aync #444
• Redesign of InputSpan and OutputSpan #439
• Improve handling of tags with the processBulk Consumable/PublishableRange API #407