A computer system for modeling and using a data element to be included as a component of an electronic communication comprising: a repository having stored therein predefined data elements for use by a computer system in identifying information portions in an electronic communication document to be sent from the computer system to another computer system, each of the predefined data elements being associated with semantic information indicating its definition and intended use; a graphical user interface; and a modeling tool that, upon a first user input by a user to make a selection, displays any of the predefined data elements for editing in said graphical user interface, the modeling tool presenting the semantic information for the selected data element in said graphical user interface, changes to the predefined data elements being saved in the repository, wherein, upon receiving the electronic communication document, the other computer system can recognize and use the predefined data elements to interpret and process a content of the electronic communication document and to display the information portions identified by the predefined data elements, wherein the modeling tool is further adapted to modify at least one aspect of the semantic information based on a second user input made under guidance of the modeling tool, characterized by the modeling tool presents a user-selectable control for adding a new data element to the selected data element, the modeling tool provides that the user can select between predefined data types for the new data element, upon the user selecting one of the predefined data types, the model- ing tool provides that the user can select between predefined properties associated with the selected predefined data type a repository having stored therein predefined data elements for use by a computer system in identifying information portions in an electronic communication document to be sent from the computer system to another computer system, each of the predefined data elements being associated with semantic information indicating its definition and intended use; a graphical user interface; and a modeling tool that, upon a first user input by a user to make a selection, displays any of the predefined data elements for editing in said graphical user interface, the modeling tool presenting the semantic information for the selected data element in said graphical user interface, changes to the predefined data elements being saved in the repository, wherein, upon receiving the electronic communication document, the other computer system can recognize and use the predefined data elements to interpret and process a content of the electronic communication document and to display the information portions identified by the predefined data elements, wherein the modeling tool is further adapted to modify at least one aspect of the semantic information based on a second user input made under guidance of the modeling tool, characterized by the modeling tool presents a user-selectable control for adding a new data element to the selected data element, the modeling tool provides that the user can select between predefined data types for the new data element, upon the user selecting one of the predefined data types, the model- ing tool provides that the user can select between predefined properties associated with the selected predefined data type