Data Providers can fill recursive structures, either directly or through recursive calls.

Consider an 'Employee' transaction with the following structure:

Employee
   EmployeeId*
   EmployeeName
   BossId           subtype of EmployeeId
   BossName         subtype of EmployeeName

Example 1

Suppose it is necessary to load an employee's information into a structure (for example to send it as a parameter to another object). First, the SDT should be defined as follows:

Note that this is a Recursive SDT. Then, a Data Provider receiving the employee will solve the problem:

Where:

Output: EmployeeSDT

Collection: False

Parm( &EmployeeId );

This is a recursive Data Provider. DPLoadEmployee is calling itself to fill the recursive member of the EmployeeSDT. For example, the XML output  (DPLoadEmployee( 123 ).toXML()) would be:

 <EmployeeSDT>
    <Id>123</Id>
    <Name>John Doe</Name>
    <Manager>
        <Id>99</Id>
        <Name>Mary Shelley</Name>
        <Manager>
            <Id>69</Id>
            <Name>Ernest Jackson</Name>
            <Manager></Manager>
        </Manager>
    </Manager>
<EmployeeSDT>

Example 2

Now suppose that given an employee, we have to Output all his/her subordinates (direct or indirect), as shown below:

<SubEmployees>
    <Employee>
       <Id>99</Id>
       <Name>Mary Shelley</Name>
       <Subordinates> 
           <Employee>
              <Id>123</Id>
              <Name>John Doe</Name>
              <Subordinates>
                ...
              </Subordinates>
           </Employee>
           <Employee>
              <Id>150</Id>
              <Name>Camile Green</Name>
              <Subordinates>
                ...
              </Subordinates>
           </Employee>
            ...
       </Subordinates> 
    </Employee>
    <Employee>
	...
    </Employee>
    ....
</SubEmployees>

This can be easily done with a Data Provider.

First, it is necessary to define the Output structure (this is done using an SDT):

Second, the Data Provider itself is:

Name:   DPLoadSubordinates
Output: SubEmployees
Rules:  parm(&BossId)
 
SubEmployees
{
    Employee     where BossId = &BossId
    {
        Id = EmployeeId
        Name = EmployeeName
        Subordinates = DPLoadSubordintates( EmployeeId )
    }
}

Note that this is a recursive Data Provider (DPLoadSubordinates is calling itself).