communication data marts, the team may be r
eady to tackle the most challenging data mart of all: the Web profitability data mart.
We can build the Web profitability data mart as an extension of the sales transaction data mart. Fundamentally, we are going to allocate all the activity costs
and infrastructure costs down to each sales transaction. We could, as an alternative, try to build the Web profitability data mart on top of the clickstream,
but this would involve an even more controversial allocation process in which
we allocated costs down to each session. It would be hard to assign activity
and infrastructure costs to a session that had no obvious product involvement
and led to no immediate sale.
A big benefit of extending the sales transaction fact table is that we will get a
view of profitability over all our sales channels, not just the Web. In a way, this
should be obvious, because we know that we have to sort out the costs and
assign them to the various channels anyway. For this reason, we will call the
main fact table in our new data mart simply
profitabilityThus the grain of the profitability fact table is each individual product sold on
a sales ticket to a customer at a point in time. This sounds familiar, doesn’t it?
This grain is nearly identical to the grain of the first dimensional model we
designed. The primary difference is that Chapter 2’s schema was limited to the
grocer’s brick-and-mortar store. In this section the model will include profitability metrics across all channels, including store sales, telesales, and Web sales.
We explored a profitability data mart extensively in Chapter 5. We enumerated
a lengthy list of profit and loss (P&L) facts from gross revenue to contribution
profit. Figure 14.7 illustrates these same facts in a somewhat broader context.
As we saw in Chapter 5, the fact table is organized as a simple P&L statement.
The first fact is our now-familiar quantity sold. The rest of the facts are dollar
values, beginning with gross revenue, which is the value of the item as if it
were sold at list or catalog price. We account for allowances and promotions to
arrive at net revenue, which is the true net price the customer pays times the
quantity purchased.
The rest of the P&L table consists of a series of subtractions, where we calculate progressively for more far-reaching versions of profit. We begin by subtracting the product manufacturing cost (if we manufacture it) or, equivalently,
the product acquisition cost (if we acquire it from a supplier). We then subtract
the product storage cost. At this point many enterprises refer to this partial
result as the
gross profit
. One can divide this gross profit by the gross revenue
to get the gross margin ratio.