Keep track of graph operations

[bergie]

Currently we operate on the JSON graph format from NoFlo. That format is a good snapshot of the graph state, but what we really need is a format recording the graph state as a history of operations performed on it.

So instead of having a list of nodes, you'd have a history of operations like Add node Foo.

This would enable multiple useful things:

• Infinite undo
• Easier implementation of real-time collaboration
• "Replaying" graph creation as a teaching tool, consider flowcasts, maybe even synchronized with audio/video recorded from the collaboration session

Here is some argumentation for the importance of undo:

• http://sachagreif.com/undo/
• http://alistapart.com/article/neveruseawarning

In the case of NoFlo UI, having easy availability to undo would also have the benefit of making our various gestures a lot safer, as you can always step back.

On implementation:

• ShareJS JSON operations format: https://github.com/share/ottypes/wiki/JSON-operations
• dataflow operation logger: https://github.com/meemoo/dataflow/blob/master/src/plugins/log.js#L49
• JSON patch: http://tools.ietf.org/html/rfc6902
• Jsonary and especially the undo plugin
• Writing an Operational Transformation library, part 2, gist

[bergie]

@jonnor has put some thought into this with GEGL: https://git.gnome.org/browse/gegl/tree/docs/journal.txt

The text/event-stream format might be suitable for storage: https://developer.mozilla.org/en-US/docs/Server-sent_events/Using_server-sent_events#Event_stream_format

[bergie]

It might make sense to follow the same operations convention as in the Graph protocol

[alfa256]

A journal file is desirable for the purpose of documentation, e.g: How to add plug-ins to this program? And the recorded operations show the process of connecting a new plug-in component to the system step by step.
Another approach for existing flows can be a semantic diff between the json representations of them. Changes on iips, process names ( detected if the same component has the same connections as before ), component names ( detected if process name and connections stay the same), changes on connections, positions based on the metadata, icon, etc.

[jonnor]

Yes, we ideally want to enable playback of the creation of a graph in a viewer, and to allow annotations like audio/video commentary

[jonnor]

I've started prototyping a backend for this now: https://github.com/jonnor/noflo/tree/graph-journal

[bergie]

The initial Graph Journal has now been merged into NoFlo: noflo/noflo#139

[jonnor]

#93