When at full employment level of income, AD is greater than AS, the excess of AD over AS is termed as "Excess Demand".
Showing the concept of Excess 1demand, diagrammatically, we use the concept of "Inflationary Gap". (Shown by CD in the diagram).

Point E, denotes the point of equilibrium, as at this point AD curve intersects the 45° Line. OM is the equilibrium income. OF denotes full employment level of income. At this level DF denotes aggregate supply, (Since income is same as Aggregate Supply). But the Aggregate Demand (AD) at full employment is CF, It means that AD (CF) is more than what is required to sustain full employment output. It denotes a situation of Excess Demand equal to CD(CF-DF), which denotes "Inflationary Gap".
To correct inflationary gap, the following measures can be taken:

1. Reduce government spending (Fiscal measure), which will directly reduce AD and thereby remove the inflationary gap.
2. The central bank can raise the bank rate, as a result the commercial banks are compelled to raise their lending rate, so demand for loans will fall. This is turn will reduce investment and in turn reduce AD in the economy.