Stable identity
Assignments refer to player IDs, so IDs must be unique inside a play and remain stable when descriptive labels or coordinates change.
Football meaning
Position and alignment are separate: position identifies a roster role, while alignment explains where and how that player begins this play.
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Football meaning example
{
"id": "x",
"position": "WR",
"label": "X",
"initialCoordinate": {
"x": 5,
"y": -1
},
"alignment": "Wide left",
"side": "offense"
}