The Shlaer–Mellor method is one of a number of software development methodologies which arrived in the late 1980s. Most familiar were Object-Oriented Analysis and Design (OOAD) by Grady Booch, Object Modeling Technique (OMT) by James Rumbaugh, Object-Oriented Software Engineering by Ivar Jacobson and Object-Oriented Analysis (OOA) by Shlaer and Mellor. These methods had adopted a new object-oriented paradigm to overcome the established weaknesses in the existing structured analysis and structured design (SASD) methods of the 1960s and 1970s. Of these well-known problems, Shlaer and Mellor chose to address: