Editing XBRL (section)

====Calculation Linkbase====
This linkbase associates concepts with other concepts so that values appearing in an instance document may be checked for consistency.

The idea of the calculation linkbase is to improve the quality of an XBRL report. It contains definitions of basic validation rules, which apply to all instance documents referring to a particular taxonomy. A hierarchical calculation linkbase sorts all monetary elements in this way so that lower level elements sum up to or are subtracted from one another so that the upper level concept is the result of these operations.

The sign of the relationship depends on the weight attribute that is assigned to the arc connecting two elements. An example is provided below.

<syntaxhighlight lang="xml">
<calculationArc xlink:type="arc" 
 xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" 
 xlink:from="GrossProfit" xlink:to="RevenueTotal" 
 order="1" weight="1" use="optional"/>
<calculationArc xlink:type="arc"
 xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item"
 xlink:from="GrossProfit" xlink:to="CostOfSales" 
 order="2" weight="-1" use="optional"/>
</syntaxhighlight>

The example shows that there are defined two calculation arcs providing details concerning relations between Gross profit, Revenue and Cost of Sales. In Income Statements, Gross profit is the difference between the other two.
Therefore, we assign weight attribute value to "1" on the arc connecting Gross profit and Revenue and "-1" between Gross profit and Cost of Sales.
The reason why there is a difference between calculation and presentation linkbases, is that the total element that stands for the summation of all others usually appears at the bottom in the financial statements whereas in the calculation linkbase it must be placed as the top concept.

<pre>
Presentation 	Calculation 
Assets (Presentation)	 	             Assets, Total	 
 	Assets, Non-Current	 	 	Assets, Non-Current	+1
 	Assets, Current	 	 	        Assets, Current	        +1
 	Assets, Total	 	 	 	 
</pre>

There are two major rules concerning calculation relations in XBRL.
Firstly, we cannot carry out operations on elements that have different values of the periodType attribute. This is often called the cross-context rule and relates to defining some elements as "For period" (duration) and others as "As of date" (instant). For example, concepts that appear on the Balance Sheet are instant: which means that their value is presented for a specified day, while elements in the Income Statement or Statement of Cash Flows are duration: because they represent actions that took place over a period of time. The problem emerges for example in the Statement of Changes in Equity or Movements in Property, Plant and Equipment where instant elements mix with duration. The solution to this problem is a formula linkbase that will provide taxonomy creators with many more functions than just simple addition or subtraction.
Secondly, the double entry accounting rule requires XBRL taxonomy creators to define the credit/debit nature of monetary elements appearing in the Balance Sheets and Income Statements. This rule does not only disallow the addition of elements with opposite balance attributes—they must be subtracted—it also defines whether the numerical value contained within an element should be positive or negative.