Boxology is the essence of software architecturedescription. In comparison with text-based languages,well-defined visual notations model software architectureat a high level of abstraction. They are easy to understandand easy to use due to its simplicity, but less expressive asmany architectural properties can not be adequatelyrepresented. A key question to be answered in the designof a visual notation for the description of softwarearchitectures is what properties should be visuallyrepresented. This paper applies the theory of design spacein the development of a visual notation called ExSAVN forsoftware architectural modeling. It is based on the designspace of software architectural elements to determine theproperties of software architectures that are visuallyrepresented. It achieves balance between simplicity andexpressiveness and supports incremental and iterativearchitectural design through a number of high levellanguage facilities, which include the representation ofundecided properties, hierarchical abstraction and typedefinition facilities. The paper also illustrated the style ofExSAVN by some examples of real systems.