Subsystems and edge groups

"The graph canvas" covered selecting more than one node at a time. This page covers the two things a multi-node selection is actually for: edge groups, which let several relationships share one equation, and subsystems, which collapse a selection into a single navigable unit. Both continue on the bundled "Thermal Management" example, three nodes: a battery module, its enclosed air volume and its electrical losses.

Edge groups

The example starts with two relationships: Battery module drives both Enclosed air and Electrical losses, but Enclosed air and Electrical losses have no direct relationship of their own yet. Select both of them and the toolbar's Create edge group icon lights up.

An edge group doesn't ask which one is the source. With more than two members it builds a full mesh, one directed relationship each way between every pair, and applies a single equation across every edge in it at once.

There are no clickable reference chips here, unlike a hand-authored relationship's own equation field. With a group, the exact set of available states depends on which members are previewed, so the editor states them as plain text instead ("Available references: ...") for you to type into the equation.

Saving closes a fresh mesh edge onto the canvas: the relationship count jumps from 3 to 5 for a two-member group (one pair, both directions).

A member can be detached from its group later without losing its edges. They just become ordinary, independently-editable relationships instead of shared ones. Deleting the group only removes the mesh edges still shared by whatever members remain in it.

Subsystems

Select two (or more) nodes and the Create subsystem icon enables the same way. Unlike an edge group, a subsystem doesn't touch any equations. It's purely organizational, collapsing the selection into one proxy you can navigate into.

Wrapping Battery module and Enclosed air together collapses both into a single "Thermal enclosure" proxy. Every relationship that used to cross between a wrapped node and something outside it becomes a boundary port instead of disappearing. The proxy here reports 3, matching the battery's link to Electrical losses plus the new two-way mesh from the edge group above.

Clicking the proxy enters it: a breadcrumb replaces the usual node/relationship count, and the wrapped members reappear, editable exactly as before.

Wrapping and unwrapping are each a single undoable step, same as everything else on the canvas. There's no separate "flatten this subsystem" action to look for; undo does it.

Where to go from here

Both features so far have been about organizing a model that's already valid and already runnable. Next: actually running one, offline and paced, and reading back more than a single number from the result.