This invention has as its object to provide an information processing apparatus which can process an event generated upon changing an attribute value at high speed. This invention is directed to an information processing apparatus which parses an XML document and converts it into a DOM tree, and has the following characteristic, feature. Upon reception of an operation instruction by the user (step S312), it is checked if the instruction is an instruction including a change of an attribute value (step S313). If it is determined that the instruction is the instruction including the change of the attribute value, type information of the attribute value is acquired, and an event that describes the type information and the instruction contents is generated (steps S315-S318). An event handler processes the instruction contents in accordance with the type information (step S322).