For embodying "Ubiquitous Computing" and "Context- awareness" into smart space design, an interactive model based on "Direct Manipulation" and a smart spatial interface mediated by PDA is demonstrated in this study to emphasize the user's initiative in actuating smart services in space. By the metaphor of WIMP (i.e. Window, Icon, Mouse and Popup-menu) inherited from computer desktop GUI, electronic services and digital information are bundled into physical objects in smart space. For implementation, versatile IT technology and spatial setting are integrated in laboratory, including the RFID, Wi-Fi 802.11 and IR network for context-sensing, device-controlling and service actuation. Through the evaluation in lab demo scenarios, the findings are as follows: (1) the cognitive mapping structure between digital and physical objects derives innovative research issues in user's spatial representation and object labelling for both individuals and groups; (2) the real-time mapping between spatial setting and user status abstracted from sensing network provides rich support for direct manipulation interactions for smart applications; (3) the PSA provides for the habitant extended ability of handheld control-and-display for almost everything.