We often create different kinds of messages such as exam change notices, classroom change notices, bug reports, old exams, assignment solutions, requests for class absences, requests for postponement of exams, requests for placing papers/books in the library, and so on. However, traditional mail supports completely untyped and unstructured mail, and thus cannot capture the differences between different kinds of messages. Information Lens [] overcomes this problem by supporting typed messages, allowing users to define these types, and arranging the types in a type hierarchy.
In general, typing a message offers several benefits: First, a type defines a structure that is common to all its instances, which can be created automatically by the system. For instance, an exam change notice would have fields for new and old dates, which can be automatically created by the system. Messages in Information Lens are considered semi-structured since they are associated with text fields that can have arbitrary contents. Second, a type can be used as a basis for selecting messages from a mail box. For instance, we can ask the mail system to show all ``notices'' or all ``exam notices''. Third, if we want to exchange objects created by other applications such as spreadsheets and wordprocessors, then we are not forced to convert between their representations and the textual representation understood by traditional mail systems. Finally, the mail system can directly display multiple representations of these objects, as illustrated by contemporary mail systems supporting MIME attachments.