Santa Monica-based Cornerstone OnDemand debuted on the markets Thursday in a strong showing, trading as high as $20.25 after its IPO debut a $13.00 per share. The firm was trading around $19.60, or 50 percent above its debut price in morning trading. The firm, headed by Adam Miller, develops software-as-a-service for human resources and talent management. Cornerstone is trading on the NASDAQ Global Market as CSOD. The firm priced last night at $13.00, well above its initial $9 to $11 estimated initial pricing range. Cornerstone OnDemand was venture backed by Bay Partners, Bessemer Venture Partners, and Meritech Capital. The firm is just the latest in a string of well received IPOs in Southern California, including Demand Media, RealD, Inphi Corp., MaxLinear, Green Dot, and ReachLocal.