1. An information processing apparatus which processes tree structure data converted from an XML document, wherein the tree structure data includes a numerical value of an attribute, comprising: a determination unit configured to, when an operation instruction is input, determine whether or not the operation instruction is an instruction including a change of the numerical value of the attribute; a first event generation unit configured to, when said determination unit determines that the operation instruction is not the instruction including the change of the numerical value of the attribute, generate a first event which describes contents of the operation instruction in a character string format; a second event generation unit configured to, when said determination unit determines that the operation instruction is the instruction including the change of the numerical value of the attribute, acquire type information of the numerical value of the attribute from the tree structure data and generate a second event which describes the type information of the numerical value of the attribute and contents of the operation instruction; a reception unit configured to receive at least one of the first event generated by the first event generation unit and the second event generated by the second event generation unit; a first event processing unit configured to process, upon reception of the first event, the first event as the character string format, said first event processing unit being a central processing unit; a second event processing unit configured to process, upon reception of the second event, the second event as the format of type information without converting the second event from the character string format to the format of the type information.