Function Name	Equal
Category	Comparator
Icon
Description	Determine whether one value is equal to another
Inputs	Value 1 Value that must be equal to Value 2 for a true output Value 2 Value to check Value 1 against
Outputs	Result Boolean indicator - true if Value 1 is equal to Value 2, false otherwise
Properties	None -

Usage

The Data Mapper Comparator Equal function allows you to determine whether one value is equal to another. The values in question may be from the input data source or components within the Mapper, such as Constants or function outputs. Since the Equal function outputs a boolean value, it is most usefully used in conjunction with other functions such as Set and Logic components. To apply the Comparator Equal function, use the following process:

Create a new Data Mapper file, dragging your XML data source and targets into the editor area. For this example we are using staff_source.xsd, an XML Schema Definition inferred from the following source:

<staff>
 <employee>
  <first_name>Mark</first_name>
  <second_name>Brown</second_name>
  <started>2001</started>
  <permanent>true</permanent>
 </employee>
 <employee>
  <first_name>Jane</first_name>
  <second_name>Jackson</second_name>
  <started>1998</started>
  <permanent>true</permanent>
 </employee>
 <employee>
  <first_name>Joe</first_name>
  <second_name>Simpson</second_name>
  <started>2008</started>
  <permanent>false</permanent>
 </employee>
 <employee>
  <first_name>Lynn</first_name>
  <second_name>Nicolson</second_name>
  <started>2008</started>
  <permanent>false</permanent>
 </employee>
</staff>

For our target schema we will be using staff_target.xsd, inferred from the following XML:

<company>
 <staff_member since="2000" contract="false">
  <f_name>Ken</f_name>
  <s_name>Jones</s_name>
 </staff_member>
 <staff_member since="2003" contract="true">
  <f_name>Linda</f_name>
  <s_name>Lee</s_name>
 </staff_member>
 <staff_member since="1998" contract="false">
  <f_name>Paul</f_name>
  <s_name>Mitchell</s_name>
 </staff_member>
</company>

The data models employees within an organisation. Let's assume that, rather than mapping all data values, we only want to map "employee" elements representing staff members who started working at the company in one particular year, i.e. whose "started" values are 2008. Here is the Data Mapper with Source and Target imported:

Drag the Comparator Equal function from the Component Palette into the mapping area:

The Equal function takes two inputs representing the values you want to compare. The function output will indicate true if Value 1 is equal to Value 2, and false if it is not. Both inputs and output of the Equal function may be connected to items in the XML Reader/ Writer or other components in the Mapper.

Since we want to map only elements whose "started" values are 2008, connect the "started" output in the XML Reader to the Value 1 input in the Equal function.

Now we need to define the value to match the "started" output to. Drag a Constant Value from the Data Type section onto the Mapper. Right-click it and choose Show Properties. Enter an integer type as the Data Type and 2008 as the Value.

Connect the Constant output to the Value 2 input in the Equal function.

Now each time the Mapper encounters the "started" element, it will check whether it is equal to 2008. If it is, the function will output a value of true, otherwise it will output a value of false. Let's now use this information to filter our data. Drag a Filter function from the Set section onto the Mapper. Connect its Bool input to the output of the Equal function and its Nodes input to the "employee" output in the XML Reader.

Now connect the output of the Filter function to the "staff_member" input in the XML Writer. This will ensure that an "employee" element is only mapped if its "started" value is 2008.

Finally let's make the remaining input and output connections. Remember to map "started" to "since" - although we have used this value from the source we have not yet instructed the Mapper to map it.

We can now execute the transform by pressing Shift-F5 or the Execute button (). The transform is applied and the file we selected as output opens in the editor:

<company>
 <staff_member since="2008" contract="false">
  <f_name>Joe</f_name>
  <s_name>Simpson</s_name>
 </staff_member>
 <staff_member since="2008" contract="false">
  <f_name>Lynn</f_name>
  <s_name>Nicolson</s_name>
 </staff_member>
</company>

The output only contains those "staff_member" records who started in 2008. Most of the Comparator functions are particularly useful when you need to filter or transform your data depending on an unknown range of input values.