Oracle9i OLAP Developer's Guide to the OLAP DML Release 2 (9.2) Part Number A9529801 

Working with Models, 2 of 8
A model is a set of interrelated equations that can assign results either to a variable or to a dimension value. For example, in a financial model, you can assign values to specific line items, such as gross.margin
or net.income
.
gross.margin = revenue  cogs
If an =
command assigns data to a dimension value or refers to a dimension value in its calculations, then it is called a dimensionbased equation. A dimensionbased equation does not refer to the dimension itself, but only to the values of the dimension. Therefore, if the model contains any dimensionbased equations, then you must specify the name of each of these dimensions in a DIMENSION
command at the beginning of the model.
If a model contains any dimensionbased equations, then you must supply the name of a solution variable when you run the model. The solution variable is both a source of data and the assignment target of model equations. It holds the input data used in dimensionbased equations, and the calculated results are stored in designated values of the solution variable. For example, when you run a financial model based on the line
dimension, you might specify actual
as the solution variable.
Dimensionbased equations provide flexibility in financial modeling. Since you do not need to specify the modeling variable until you solve a model, you can run the same model with the actual
variable, the budget
variable, or any other variable that is dimensioned by line
.
Suppose that you define a model, called income.calc
, that will calculate line items in the income statement.
define income.calc model ld Calculate line items in income statement
After defining the model, you can use the MODEL
command or the OLAP Worksheet editor to specify the contents of the model. A model can contain DIMENSION
commands, = commands, and comments. All the DIMENSION
commands must come before the first equation. For the current example, you can specify the lines shown in the following model.
DEFINE INCOME.CALC MODEL LD Calculate line items in income statement MODEL DIMENSION line net.income = opr.income  taxes opr.income = gross.margin  (marketing + selling + r.d) gross.margin = revenue  cogs END
When you write the equations in a model, you can place them in any order. When you compile the model, either with the COMPILE
command or by running the model, the order in which the model equations are solved is determined. If the calculated results of one equation are used as input to another equation, then the equations are solved in the order in which they are needed.
To run the income.calc
model and use actual
as the solution variable, you execute the following command.
income.calc actual
If the solution variable has dimensions other than the dimensions on which model equations are based, then a loop is performed automatically over the current status list of each of these "extra" dimensions. For example, actual
is dimensioned by month
and division
, as well as by line
. If division
is limited to ALL
, and month
is limited to OCT96
to DEC96
, then the income.calc
model is solved for the three months in the status for each of the divisions.
If a model contains an = command that assigns data to a dimension value, then the dimension is limited temporarily to that value, performs the calculation, and then restores the initial status of the dimension.
For example, a model might have the following commands.
DIMENSION line gross.margin = revenue  cogs
If you specify actual
as the solution variable when you run the model, then the following code is constructed and executed.
PUSH line LIMIT line TO gross.margin actual = actual(line revenue)  actual(line cogs) POP line
This behindthescenes construction lets you perform complex calculations with simple model equations. For example, line item data might be stored in the actual
variable, which is dimensioned by line
. However, detail line item data might be stored in a variable named detail.data
, with a dimension named detail.line
.
If your analytic workspace contains a relation between line
and detail.line
, which specifies the line item to which each detail item pertains, then you might write model equations such as the following ones.
revenue = total(detail.data line) expenses = total(detail.data line)
The relation between detail.line
and line
is used automatically to aggregate the detail data into the appropriate line items. The code that is constructed when the model is run ensures that the appropriate total is assigned to each value of the line
dimension. For example, while the equation for the revenue
item is calculated, line
is temporarily limited to revenue
, and the TOTAL
function returns the total of detail items for the revenue
value of line
.

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