A software platform for health care that began under Parkland Memorial Hospital has spun off into a Dallas-based tech startup and raised $21.6 million from venture capital firms, Dallas investors and hospital systems. The software project was initially part of the Parkland Center for Clinical Innovation, a nonprofit that researches ways to improve health outcomes. The software helps clinicians track patients’ medical histories, identify risk factors and intervene early. It also allows community-based organizations, such as food banks, to communicate with doctors and nurses about social factors like homelessness that could endanger a patient’s health.