The firm's risk-analytics layer. Limit-checking tells you if the book is inside the box; this tells you what the book is actually betting on. A Barra-style model decomposes the consolidated firm book onto six tradable factors — market, size, value, momentum, quality, low-vol — by time-series regression, then splits risk into systematic vs idiosyncratic, estimates VaR / Expected Shortfall, stress-tests the book against historical scenarios and sizes the factor hedges that would neutralise an unwanted bet.