Before revision:  Through a rumor-spreading system dynamic, a digital goods vendor can capture market share by focusing efforts on software quality, which is costly. We first derive theoretical results expressing market share, the state variable, in terms of effort put towards quality, the control variable. We then usenumerical examples to illustrate optimal control paths for vendors facing various market conditions. Our results on effort towards quality are consistent with software evolution theory and show that focus on quality always declines over a product's life cycle.
After revision:  Through a rumor-spreading system dynamic, a digital goods vendor can capture market share by focusing costly effort on post-launch product maintenance, which influences user perception of the product and drives a revenue stream associated with product use. Our theoretical results show necessary and sufficient conditions for product maintenance to decline over a product's life cycle.