This excerpt taken from the MSCS 10-K filed Apr 17, 2006.
On April 19, 2002, we completed the acquisition of the outstanding common stock of Mechanical Dynamics, Inc. (MDI) through a tender offer. MDI developed, marketed and supported functional virtual prototyping solutions that expanded our core software offerings, complemented our existing product and service offerings and increased our presence in the product lifecycle management market to better serve customers. The acquisition of MDI has been accounted for as a purchase, and accordingly, the results of operations of MDI since April 19, 2002 are included in our consolidated statements of operations. See Note 3Business Acquisitions in Notes to Consolidated Financial Statements.