1. MORENA: A Middleware for Programming
NFC-enabled Android Applications as
Distributed Object-Oriented Programs
Andoni Lombide Carreton
Kevin Pinte
Wolfgang De Meuter
ACM/IFIP/USENIX 13th International Conference on Middleware 2012
December 5 2012
Montreal, Canada
Monday 28 January 13

2. RFID in Android
• NFC (touch range).
NdefMessage: {
• Callback on activities ,
to detect RFID tags
with subscribed MIME- , NdefRecord
type in memory. byte array
}
• File access abstraction
read write
Monday 28 January 13

3. Drawbacks of the Android NFC API
• Manual failure handling (and NFC causes A LOT of failures because of its
hardware characteristics).
• Blocking communication (Android documentation recommends to use a
separate thread for many RFID operations).
• Manual data conversion
• Tight coupling with activity-based architecture
Monday 28 January 13

4. Lessons Learnt from Previous Ambient-Oriented
Programming Research
• Using objects as first class software representations for RFID-tagged “things”
is a nice abstraction.
• These objects can be directly stored in the RFID tags’ memory to minimize
data conversion.
• Event-driven discovery (fortunately built-in into Android).
• Asynchronous reads and writes.
Monday 28 January 13

5. Middleware Architecture
Application
Thing level One middleware
for Android 4.0
Tag level or higher
Android
Monday 28 January 13

6. Evaluation: WiFi Sharing Application
Monday 28 January 13

7. Evaluation: WiFi Sharing Application
Monday 28 January 13

8. Things
From now on, we don’t
public class WifiConfig extends Thing { have to worry about the
public String ssid_;
activity anymore.
public String key_;
public WifiConfig(ThingActivity<WifiConfig> activity, String ssid, String key) {
super(activity);
ssid_ = ssid;
key_ = key;
}
public boolean connect(WifiManager wm) {
// Connect to ssid_ with password key_
};
Supported serialization:
}
- JSON-serializable fields.
- Skipping transient fields.
- Deep serialization, no cycles.
Monday 28 January 13

9. Initializing Things
As soon as an empty
tag is detected
@Override
public void whenDiscovered(EmptyRecord empty) {
empty.initialize(
myWifiThing,
new ThingSavedListener<WifiConfig>() {
@Override
public void signal(WifiConfig thing) {
toast("WiFi joiner created!");
}
},
new ThingSaveFailedListener() {
@Override
public void signal() {
toast("Creating WiFi joiner failed, try again.");
}
});
}
Monday 28 January 13

10. Discovering and Reading Things
As soon as a WifiConfig
tag is detected
@Override
public void whenDiscovered(WifiConfig wc) {
toast("Joining Wifi network " + wc.ssid_);
wc.connect();
}
Contains cached fields for
synchronous access.
Physical reads must be
asynchronous.
Monday 28 January 13

11. Saving Modified Things
myWifiConfig.ssid_ = "MyNewWifiName";
myWifiConfig.key_ = "MyNewWifiPassword";
myWifiConfig.saveAsync(
new ThingSavedListener<WifiConfig>() {
@Override
public void signal(WifiConfig wc) {
toast("WiFi joiner saved!");
}
},
new ThingSaveFailedListener() {
@Override
public void signal() {
toast("Saving WiFi joiner failed, try again.");
}
});
Monday 28 January 13

12. Broadcasting Things to Other Phones
Will trigger whenDiscovered on the
receiving phone with the broadcasted thing
myWifiConfig.broadcast(
new ThingBroadcastSuccessListener<WifiConfig>() {
@Override
public void signal(WifiConfig wc) {
toast("WiFi joiner shared!");
}
},
new ThingBroadcastFailedListener<WifiConfig>() {
@Override
public void signal(WifiConfig wc) {
toast("Failed to share WiFi joiner, try again.");
}
});
Monday 28 January 13

13. Evaluation: WiFi Sharing Application
Monday 28 January 13

14. Middleware Architecture
Application
Thing level One middleware
for Android 4.0
Tag level or higher
Android
Monday 28 January 13

15. Detecting RFID Tags
new MyTagDiscoverer(this,
THING_TYPE,
new NdefMessageToStringConverter(),
new StringToNdefMessageConverter());
private class MyTagDiscoverer extends TagDiscoverer {
@Override
public void onTagDetected(TagReference tagReference) {
readTagAndUpdateUI(tagReference);
}
@Override
public void onTagRedetected(TagReference tagReference) {
readTagAndUpdateUI(tagReference);
}
}
Monday 28 January 13

16. The Tag Reference Abstraction
Monday 28 January 13

17. Reading RFID Tags
tagReference.read(
new TagReadListener() {
@Override
public void signal(TagReference tagReference) {
// tagReference.getCachedData()
}
},
new TagReadFailedListener() {
@Override
public void signal(TagReference tagReference) {
// Deal with failure
}
});
Monday 28 January 13

18. Writing RFID Tags
tagReference.write(
toWrite,
new TagWrittenListener() {
@Override
public void signal(TagReference tagReference) {
// Handle write success
}
},
new TagWriteFailedListener() {
@Override
public void signal(TagReference tagReference) {
// Deal with failure
}
});
Monday 28 January 13

19. Fine-grained Filtering
private class MyTagDiscoverer extends TagDiscoverer {
@Override
public void onTagDetected(TagReference tagReference) {
readTagAndUpdateUI(tagReference);
}
@Override
public void onTagRedetected(TagReference tagReference) {
readTagAndUpdateUI(tagReference);
}
@Override
public boolean checkCondition(TagReference tagReference) {
// Can be used to apply a predicate
// on tagReference.getCachedData()
}
}
Monday 28 January 13

20. Conclusion
• Event-driven discovery.
• Non-blocking communication:
• Things: cached copy, asynchronous saving of cached data.
• TagReferences: first class references to RFID tags offering asynchronous
reads and writes.
• Automatic data conversion
• Looser coupling from activity-based architecture
• Data structures over several tags, stronger consistency guarantees?
Monday 28 January 13

21. MORENA: A Middleware for Programming
NFC-enabled Android Applications as
Distributed Object-Oriented Programs
Andoni Lombide Carreton
Kevin Pinte
Wolfgang De Meuter
ACM/IFIP/USENIX 13th International Conference on Middleware 2012
December 5 2012
Montreal, Canada
Monday 28 January 13