Initializing data nodes with constants in mapping activity?

Hi experts,

In a process i have a complex data structure node with 0..n cardinality. How can i initialize it at the beginning of the process with constant values.

e.g. my structure is like:

ComplexStruct

- string 0..1 name

- string 0..1 url

and in a mapping step i want to init it with:

ComplexStruct

+[0] name="Name1"

        url = "URL1"

+[1] name="Name2"

        url = "URL2"

+[2] name="Name3"

        url = "URL3"

Can anybody help me on this? Is there any documentation on this?

Regards

Michael