On Meta-Management of
Spatio-Temporal Data
Goce Trajcevski
DbSN Lab
Dept. of EECS
Northwestern University
goce@eecs.northwestern.edu
Joint work with:
Zachary Bischof, Oliviu Ghica, Nikoly Valtchanov, Peter Scheuermann
IGERT-UIC-Sep09
Pre-Motivation
Context: Any information pertaining to a given situation that can
be used to characterize the entities of interest – e.g., GUIDE project
Personal (location, interests, preferred meals)
 Environmental (time of day, locations of
Situation?
attractions

time
predictable
attributes
IGERT-UIC-Sep09
place
Unpredictable
(instantaneous) attributes
with continuous impact
Pre-Motivation –Combined Situational Awareness
Nurse on duty in Assisted Living Residence
 Resident experiences high temperature
and manifests food poisoning
Physician is the nearest hospital is aware and
monitors
The symptoms worsen
 Physician decides to send ambulance
The number of residents with similar symptoms
dramatically increases in a short time
Not enough nurses
Not enough physician on staff in the nearest ER
Not enough many ambulances
IGERT-UIC-Sep09
Pre-Intro: Context-Awareness in Distributed Dynamic Settings
“If an object has been continuously moving
towards RI for more than 5min.,
begin tracking it with at least 2 cameras
when it gets closer than 100 yards.
Subsequently, if that object is identified as
human carrying a bag, maximize the focus
of the closest camera, and transmit its stream
to the monitor in the closest patrol vehicle”.
Outline
Background

Active Databases and ECA (++)
Mobility and Evolving Reactive Behavior
(ECA)2 and Meta-Triggers
Experimental Observations
Concluding Remarks
IGERT-UIC-Sep09
Background: Active Databases
Evolution = insert; delete; update (…)
Integrity Constraints (IC):
-Violation?
Fix it
ECA = Basic Paradigm of the Reactive Behavior:
Triggers (AKA Active Rules)
ON
EVENT
IF
CONDITION
THEN ACTION
IGERT-UIC-Sep09
seemingly straightforward,
but incorporates an interplay
of many
semantic dimensions
Background: Active Databases
IMPORTANT:
occurrence of an “entity of interest”  detection
Event =
primitive
internal
Condition =
Action =
IGERT-UIC-Sep09
composite
external
Event Algebras:
• E1  E2 (conjunction)
• E1; E2
(sequence)
• …
typically, a query (SQL expression)
(sequence of) SQL, mostly DML, statements
Background – Active Databases
Why ECA?
Why not all: Event  Action?
After all:
-Composite Events
-Formalisms (AKA Algebras)
-Detection “tools” (e.g., Petri Nets)
-Interval vs. Instantaneous
-ENS have been around…
COST: interrupt
 context-switch
Why not all: Condition  Action?
After all:
-OPS-like ;
-Formalisms (Temporal Logic)
-Expert Systems, Deductive Databases
have been around…
COST: polling
 potential_waste…
DBMS collaborates closely with, but is NOT the OS
 events are “seen” only through the “lens” of
transactions… (e.g., insert, delete)
 conditions are SQL queries (optimized)
IGERT-UIC-Sep09
Background – Triggers in Mobile Networks
(TRG)
Base station handover:
 2G/3G mobile phones
opt for 3G connectivity
 Traffic load
TRG identifies Producers and Consumer
 Similar to “publishers “ and “subscribers” in
ENS
Serves as a “point of reference
 Ensuring a consistent enforcements of
rules/policies
NOTE: Same entities can be both consimers (of triggers) and producers (of events)
IGERT-UIC-Sep09
Background – TRG
Mobility aspects:

Routing groups formation/maintenance (e.g., cluster-head selection)
Roadside base station
Inter-vehicle
communications
Vehicle-to-roadside
communications
VSN-enabled vehicle
Sensors
Video
IGERT-UIC-Sep09
Chem.
Systems
Storage Proc.
Background – TinyDB and Triggers
SQL:
SELECT AVG(volume)
FROM sensors
WHERE floor = 6
GROUP BY room
HAVING AVG(volume) > threshold
SAMPLE PERIOD 30S
ECA-triggers?
(so called, actuation queries)
SELECT nodeid, temp
FROM sensors
WHERE temp > threshold
OUTPUT ACTION power-on(nodeid)
SAMPLE PERIOD 10s
Event-Based:
ON EVENT bird-detect(loc)
SELECT avg(LIGHT), AVG(temp), event.loc
FROM sensors AS s
WHERE dist(s.loc, event.loc) < 10m
SAMPLE PERIOD 2s FOR 30s
IGERT-UIC-Sep09
(ECA)2 – Evolving and Context-Aware
Event-Condition-Action
Active Databases


Expert Systems (OPS5)
Events Management
Triggering Engine
IGERT-UIC-Sep09
 Events Notification Systems
 Continuous Queries Processing
Triggers and Mobile Nodes
 TinyDB
 Why/What else?
Postulate:
 In many dynamic settings, the
need for detecting a particular
event(s) and/or monitoring particular
conditions arises only after:
1. certain events have been detected
2. certain continuous conditions (do
not) hold
The perception of “event” and
“condition” can vary (especially in
distributed settings)
Meta-Management – Definition
Data
 tuples; objects; etc.
Meta-Data
 Data “about the data”
 Types, Schemas, etc.
Data Management
 Storage/retrieval
 Efficient query processing
Meta-Management


Which queries to be processed when;
How to steer the data generation/gathering
 And do it efficiently, with some QoD guarantees…
IGERT-UIC-Sep09
Evolving Reactive Behavior
WHEN an object is continuously_moving_towards
the region R for more than 5 min., IF there are less
then 10 jets in the base B1, then send alert_b to
the armored unit A1.
Air-Base B1
R
Also send alert_a to the infantry regiment
I1, WHEN *that* object is closer than 3
miles to R, IF all the marine units are
further than 5 miles from R.
To send, or not to send…
A little “algorithmic-flavor”:
continuously_moving_towards R for  6 min.
1. Generate the Voronoi diagram
2. “Shoot-a-ray take-a-walk”
3. Update the
time_accumulator
accordingly!!!
IGERT-UIC-Sep09
A
F
E
B
C
D
Triggers for that Evolving Reactive Behavior
Trigger:
ON E_Moving_Towards(O,’R’,5,T)
IF Jets_Count(‘B1’,X,T) and X<10 AND T1>=T
AND within_event(E_Moving_Towards(O,’R’,5,T1))
THEN Alert(‘b’,’A1’)
(also): Span
Consumed-by-Parent = no, Consume-Parent = no
ON E_Distance(O,’R’,3,T2)
IF Distance(‘Marines’,’R’,Y,T2) AND T2>T AND Y>=5
THEN Alert(‘a’,’I1’)
No longer Moving-Towards
Event
Moving-Towards
Detected
IGERT-UIC-Sep09
Distance Event Detected = CHILD OF THE ORIGINAL TRIGGER
(ECA)2 – Evolving and Context-Aware
Event-Condition-Action
When the body network of a resident signals
readings which have been continuously approaching
a threshold value for longer then 3 min.
If the number of on-site physicians < number of
endangered residents
Notify the nearest k hospitals, requesting
emergency vehicles with/without physicians
Subsequently,
When some of the k ambulances en-route experiences heavy traffic congestion,
If the delay in the expected arrival time is > 50% (with respect to the original arrival time)
Notify another hospital, requesting emergency vehicle…
IGERT-UIC-Sep09
(ECA)2 – Evolving and Context-Aware
Event-Condition-Action
ON E_Increase(Signal,3, patient_i, T)
IF Physician_Count(T,m) AND Endangered_Patients(T,n) AND m < n
AND within_validity(Signal,patient_i)
THEN Alert_Nearest_Hospitals(Ha,k)
Fork:
Consumed-by-Parent = yes, Consume-parent = no
ON Traffic_Abnormality(T1,V1)
IF Expected_Arrival(V1,T2,T1) AND Expected Arrival(V1,T3,T)
AND T2 – T > 1.5(T3 – T1)
THEN Alert_Nearest_Hospital(Hb,1)
Event “E_Increase” detected
Event “E_Traffic_Abnormality”
IGERT-UIC-Sep09
(ECA)2 – Syntax
ON Ep(VEp) <priority> validity(Tpv /Epv(VEpv))
IF Cp1(VCp1) within_time(Tc1)/within_event(Ec1(VEc1)) THEN Ap1(VAp1)
ELSE-IF Cp2(VCp2) within_time(Tc2)/within_event(Ec2(VEc2)) THEN Ap2(VAp2)
.....
Span (child’)
Consumed-by-Parent=<yes/no>, Consume-Parent=<yes/no>
ON Ec1(VEc1) <priority> validity(Tc1v/Ec1v(VEc1v))
IF Cc11(VCc11) within_time(Tc11)/within_event(Ec11(VEc11)) THEN Ac11(VAc11)
ELSE-IF ...
Further nesting of children
Subsequently (child’’)
Consume-Parent=<yes/no>
ON Es1(VEs1) <priority> validity(Ts1v/Es1v(VEs1v))
IF Cs11(VCs11) within_time(Ts11)/within_event(Es11(VEs11)) THEN As11(VAs11)
ELSE-IF…
Further nesting of children
IGERT-UIC-Sep09
(ECA)2 and the Meta-Triggers
OBSERVE:
ON E_Moving_Towards(O,’R’,5,T)
IF Jets_Count(‘B1,X,T) and X<10 AND T1>=T
AND
within_event(E_Moving_Towards(O,’R’,5,T1))
THEN Alert(‘b’,’A1’)
It is very likely that Jets_Count(‘B1’,X,T)
will be maintained by a remote server, for
Whom a remote-request is nothing but
an instantaneous query
But, then the “local site” (monitoring “moving_towards”) will
have to “ship” such queries upon every new detection…
PLUS, it may miss some important changes at the airport in-between
updates (pull-mode)
REMEDY: 1. Tell the remote site to make the query continuous;
2. Tell the remote site to setup a trigger for certain
values of that continuous query
3. “Remember” locally that now instead of asking the
query for the condition, you are actually expecting
an arrival of an event from the airport database
(push mode!!!)
IGERT-UIC-Sep09
(ECA)2 and the Meta-Triggers
In general, initially we have a local
TR1:
ON E1
IF CRemote AND CLocal
THEN A1
Meta-Trigger
(input)
(output)
TR1’:
ON E1; (E-requested-remote; E-notification-from-remote)
AND CLocal
THEN A1
IGERT-UIC-Sep09
???
TR1-Remote:
ON E-requested-remote
IF CContinuous
THEN A(E-notification-to-remote)
(ECA)2 and the Meta-Triggers: HOW…???
WSN Programming Languages:
 “borrow” the semantics from existing paradigms

Event-driven; SQL-based; Functional/dynamically typed
Node-Level:
 NesC; TinyScript;…


Target individual sensors and, generally, same code running on individual
nodes;
Mostly imperative; executable code (Flash); flow control based on
events/communication
Network-Level:
 TinySQL – query optimization;
 TinyScript – “more accessible” programming (dynamically typed
imperative language)
 SDlog – declarative networking; Datalog based (“@”; “#”)
Most likely, interpreted languages (Mate’; Trickle)
IGERT-UIC-Sep09
Hypothetical Reasoning
High-Level Specification (Domain-Description) Language


Based on Action Theories (well-defined semantics)
Enables hypothetical reasoning for queries
Domain Description = effects of executing actions:


A causes F1 if Fi, Fj, …, Ek, Em,…
A induces E1 when Fl, Ft, …, Er, Es, …
F = facts (i.e., tuples)
E = valid events
Plus, the expressions which define the ramifications

F1, F2, …, E1, E2, … suffice_for F/E
Action_Read_Radar induces Event_Location_Determined (NOTE: No Condition)
Event_Location_Determined, Time_Towards_Accumulator > 5 suffice_for E_Continuously_Moving _Towards
AUGMENTED WITH (ECA)2 TRIGGERS
IGERT-UIC-Sep09
Hypothetical Reasoning
Basic “vehicles” are queries of the form:
L after [A1,A2,…,An] at F1, F2, … E1, E2…
Will the Fact/Event L hold in a state which is generated
after the sequence of actions [A1, A2, …, An] is executed,
starting in a state at which F1, F2, …, E1, E2, … hold?
Design: experts from different domains involved
Deployment: status of the system and/or impact of modifications.
IGERT-UIC-Sep09
Hypothetical Reasoning
Example:
Will I have sufficient defense resources if 20 objects are continuously moving
towards R for more than 5 minutes within half an hour, approaching from
North-West, and three of them are within 3 miles.
Sufficient defense resources = More than 5 F15s in the air-base B1 and
more than 17 Type A1 Marksman in the infantry unit A1
Formally:
(Count(Airplanes(F15,B1)) > 5 AND (Count(Infantry(A1,Marksman)) > 17)
after
[ Moving_towards(X1,'R','NW',5,T1) AND Moving_towards(X2,'R','NW',5,T2)
AND … Moving_towards(X20,'R','NW',5,T20) ]
AND (T1<T2 … < T20)AND (T20 - T1 < 30) AND
[ (Distance(Xi,'R') < 3) AND (Distance(Xj,'R') < 3) AND (Distance(Xk,'R') < 3) ]
IGERT-UIC-Sep09
TelosB – Proof of Concept…
IGERT-UIC-Sep09
SID-net = Tool for hypothetical reasoning
150000x150000 ft2
(500 Mica2 Motes)
IGERT-UIC-Sep09
Simulation Observations
IGERT-UIC-Sep09
Pre-Conclusion: The “say-so” of The Network…
IGERT-UIC-Sep09
Concluding Remarks
Meta-Management of Spatio-Temporal Data



Contexts;
Evolution and Reactive Behavior with Pro-Active Consequences
Meta-Triggers;
Fabric vs. Thread…
Ongoing Work:


Translation to NDlog
 Possible “type-extensions”
Fusion with TinyDB
 Event-Base
Other popular spatio-temporal queries
Uncertainty
Distributed (meta) indexing
IGERT-UIC-Sep09
Thank You!
IGERT-UIC-Sep09
(ECA)2 Additional Example
When a patient has been continuously moving towards
the lake OR the perimeter fence for more then 5 min.
If there is no nurse within 50 ft. from him
Notify the security personnel
Subsequently,
When that person has been continuously moving along
the lake for more than 1 min.
If there is no nurse or security within 100 ft. from the lake
Notify the nurses
IGERT-UIC-Sep09
(ECA)2 – Additional Example
ON E_Moving_Towards(5, Patient, T, lake) OR E_Moving_Towards(5, Patient, T, fence)
IF Distance(Nurse, Patient, T) > 50
THEN Alert(Security, T)
Fork:
Consumed-by-Parent = no, Consume-parent = no
ON E_Moving_Along(1,Patient,T1, lake)
IF Distance(Nurse,Patient,T1) > 100 AND Distance(Security,Patient,T1) > 10
THEN Alert(Nurse, T1)
Event “E_Moving Towards”
Event “E_Moving_Along”
IGERT-UIC-Sep09