Sentient Graffiti (http://www.smartlab.deusto.es/dsg/) enables mobile users to profit from the benefits of Ubiquitous Computing in uncontrolled environments, only requiring in exchange, the participation in a community of users interested on publishing and consuming context-aware empowered annotations and services. Users annotate objects and spatial regions with multimedia data or web services which are only made available to other users when those match the contextual attributes (location range, period of time, and so forth) previously assigned to the resources.
A Sentient Graffiti can be thought of as a virtual post-it note in the form of an XML document which combines some content (multimedia presentation or web service front-end) with some keywords summarising the content, and some contextual attributes (profile of creator, location, time interval and so on) which restrict who, when and where can those annotations be seen. Those Sentient Graffitis are edited through a PC web browser or, on the move, by means of the Sentient Graffiti mobile client and then published on the system’s back-end. We currently support two types of graffiti content:
- Multimedia presentations in cut-down SMIL format (including video, audio and images).
- URLs pointing to web service front-end.
Before a graffiti can be edited and published it must be associated to:
- A spatial region (GPS).
- A Bluetooth location.
- An object using its identity given by a barcode (TRIP) or a RFID tag.
Sentient Graffiti presents a client/server architecture (see figure below) where users run a SG client in either their mobile device or a computer’s web browser, whilst a server-side component, namely Sentient Graffiti Server, stores, indexes and matches user annotations against user’s current context published by SG clients.
The generic SG Mobile Client provided enhances user to environment interaction by enabling the following four interaction mechanisms:
- Pointing – the user can point his camera phone to a bi-dimensional visual marker and obtain as result all the graffitis associated to such marker which are relevant and can be seen by him.
- Touching – the user can use a mobile RFID reader bound to a mobile through Bluetooth to touch an RFID tag and obtain all the relevant graffitis associated to that tag. There is an SG Mobile Clien implementation for Nokia NFC 6131 which eases this type of interaction by making use of the NFC properties of such device.
- Location-aware – mobiles equipped with a GPS in outdoor environments can obtain all the relevant nearby graffitis in a certain location range which are relevant to the user.
- Proximity-aware – the Sentient Graffiti mobile client can retrieve all the graffitis published in nearby accessible Bluetooth servers when the device is in Bluetooth range from the server.
