The MacSeie environment allows interoperability between two legacy healthcare systems using service oriented architecture (SOA) and HL7 v3 messages. The first system is a clinical decision support system (known as Vascular Tracker, VT) from the COMPETE III research team at St. Joseph's Healthcare Research Center in Hamilton. The second system is an electronic medical record system (EMR), which contains the medical information of patients. The VT and EMR systems are web-based and accessible through a web browser.