Assemblies

Making one item pull others along with it, so measuring the parent measures the build-up.

An item can include others. Measure the parent and the children come with it: draw 100 SF of a paving assembly and the stone, the binder and the tack coat under it are all measured at once.

Attaching a child

Attach the child to the parent from the item list, then set the rate: how much of the child there is per unit of the parent, plus an adjust multiplier for waste on that relationship alone.

Two rules decide whether the attach is allowed:

• Compatible geometry. The two must share a geometry, or one of them must be Count. An Area parent takes Area or Count children; a Count parent takes anything.
• No cycles. An item cannot include itself, directly or round a chain. The attach is refused rather than accepted and left to loop.

The rate belongs to the relationship

This is the part worth understanding, because it is what makes assemblies usable on a real job.

The rate is stored on the relationship, not on the child. The same aggregate can therefore ride one rate under a road section and a different one under a pad - one item in the list, included twice, at two rates. Editing one does not touch the other.

Pinning a unit

By default the relationship reports in the child's own unit and follows it: change the child's unit and the inclusion changes too. Pin a unit on the relationship to stop that, so a change to the child no longer ripples into this one parent.

Notes

• A child's own drawings and its included quantity are separate numbers. An item can be both measured directly and pulled in by a parent.
• Removing the relationship does not delete the child; it stops the parent pulling it.