23 lines
1.2 KiB
Markdown
23 lines
1.2 KiB
Markdown
# A Flow is a node; Source/Sink clouds are materialised nodes
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_Part of [meadows](../../README.md) · see [DESIGN.md](../../DESIGN.md)._
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In the domain `Model`, a **Flow** is a _node_ carrying `source` and `target`
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references (each to a Stock or Cloud), not an edge. The pipe you see is _rendered_
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from those references. The **Source/Sink** boundary is a **materialised Cloud
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node**, so every Flow connects node→node uniformly — no `null` ends.
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We rejected modelling a Flow as an edge (it breaks "an Information Link targets a
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Flow," since edges can't be edge endpoints, and it muddies the simulator) and
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rejected `null`-ended flows (special-casing in every graph walk and in rendering).
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## Consequences
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- The only stored edge type is the **Information Link**. Flows and Clouds are
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nodes. A reader seeing a "node that renders as a pipe" and "phantom cloud nodes"
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should look here.
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- **Cloud lifecycle** must be auto-managed: spawn a Cloud when a Flow is left
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open-ended; remove it when the Flow attaches to a Stock; never leave orphans.
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- Loop detection and the future simulator both walk a uniform node graph
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(info-links + flow→stock edges), with no boundary special cases.
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