hlights the steps needed to extend an existing mashup editor to enable seamless incorporation of JavaScript T-Rec proxies in the mashups designed. More specifically, the editor needs to add statements to import the imple- mentation locationProxy.js file that contains getLocationUpdates () function),includeJavaScriptcodetoinvoketheproxy(callgetLocationUpdate () that internally subscribes locationCallback() to receive location updates), define variables to capture the invocation output, and SO forth. All this shall be auto- matically done through interpretation of the T-Rec proxy structure. Now, let us see how the real-time charging operation can be done in a flexible way with SCL for the above scenario. Before the call is set up, the SIP INVITE is Google maps service 3rd party call Send SMS Start Location Presence Business request Finder service Figure 1.10 Call-a-Cab: integration architecture. Service Delivery Platforms <html> <head> <script type="text/javascript" language="Javascript1.2" srC-"scripts/locationProxy.js"></script> <script type="text/javascript"> var latitude;| var longitude; function callback(){ if(req. readyState==4) if (req.status latitude=req.responseXML.getElementById ('lat'); longitude=req. responseXML.getElementById ('long'); </script> </head> <body> <1-- Application specific HTML and Javascript Logic <!-- Take CellNumber as Input <1-- javascript locationProxy returns latitude and longitude respectively <script type="text/javascript"> getLocation (CellNumber); </script> <script type="text/javascript"> if (GBrowserIsCompatible()) var icon = new GIcon(baseIcon); icon. image = "http://www.google.com/mapfiles/marker.png"; var point = new GLatLng(latitude, longitude); map = new GMap2(document.getElementById("")); map.setCenter(point, 13); map.addOverlay(new GMarker (point, icon)); </script> </body> </html> Figure 1.11 Call-a-Cab: code fragment. routed through SCL, which consults the service model programmed into it by the technical expert and uses the service identifier (i.e., Business Finder) and