Reusable software components must have concise abstractions so that reuse can efficiently locate, understand, compare and select the appropriate components from component reuse library. Some principles must be followed to ensure final components for reuse which should have good performance and high reuse value. Component qualification is qualifying the different components into different level and storing them in the component reuse library according to the quality of reusable software component. Deriving metrics for the assessing the reusability level of software components is a challenging task. Many metrics exist intuitively without mathematical models. Identifying all the parameters involved in reusability metric and the inter-relationships among those parameters is also a significant challenge.