IGERT-UIC-Sep09

On Meta-Management of On Meta-Management of Spatio-Temporal DataSpatio-Temporal Data

Goce TrajcevskiDbSN Lab

Dept. of EECSNorthwestern University

goce@eecs.northwestern.eduJoint 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 attractions

time place

predictable attributes

Unpredictable (instantaneous) attributes with continuous impact

Situation?

IGERT-UIC-Sep09

Pre-Motivation –Combined Situational Awareness

Nurse on duty in Assisted Living Residence Resident experiences high temperatureand manifests food poisoningPhysician is the nearest hospital is aware andmonitors

The number of residents with similar symptomsdramatically increases in a short timeNot enough nursesNot enough physician on staff in the nearest ERNot enough many ambulances

The symptoms worsen Physician decides to send ambulance

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”.

IGERT-UIC-Sep09

OutlineOutline

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

ECA = Basic Paradigm of the Reactive Behavior:Triggers (AKA Active Rules)

ON EVENTIF CONDITIONTHEN ACTION

seemingly straightforward,but incorporates an interplayof manysemantic dimensions

Evolution = insert; delete; update (…)

Integrity Constraints (IC):-Violation? Fix it

IGERT-UIC-Sep09

Background: Active Databases

Event =

Condition =

Action =

occurrence of an “entity of interest”

primitive composite

internal external Event Algebras:• E1 E2 (conjunction)• E1; E2 (sequence)• …

typically, a query (SQL expression)

(sequence of) SQL, mostly DML, statements

IMPORTANT: detection

IGERT-UIC-Sep09

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…

Why not all: Condition Action?

After all: -OPS-like ;

-Formalisms (Temporal Logic)-Expert Systems, Deductive Databases have been around…

COST: interrupt context-switch

COST: polling potential_waste…

DBMS collaborates closely with, but is NOT the OS events are “seen” only through the “lens” oftransactions… (e.g., insert, delete) conditions are SQL queries (optimized)

IGERT-UIC-Sep09

Background – Triggers in Mobile Networks (TRG)

TRG identifies Producers and Consumer Similar to “publishers “ and “subscribers” in

ENS

Serves as a “point of reference Ensuring a consistent enforcements of

rules/policiesNOTE: Same entities can be both consimers (of triggers) and producers (of events)

Base station handover: 2G/3G mobile phones opt for 3G connectivity Traffic load

IGERT-UIC-Sep09

Background – TRG

Mobility aspects: Routing groups formation/maintenance (e.g., cluster-head selection)

VSN-enabled vehic le

Inter-vehic lecommunications

Vehicle-to-roadsidecommunications

Roadside base station

Video Chem.

Sensors

Storage

Systems

Proc.

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Background – TinyDB and Triggers

SELECT AVG(volume)FROM sensorsWHERE floor = 6GROUP BY roomHAVING AVG(volume) > thresholdSAMPLE PERIOD 30S

SQL:

ON EVENT bird-detect(loc)SELECT avg(LIGHT), AVG(temp), event.locFROM sensors AS sWHERE dist(s.loc, event.loc) < 10mSAMPLE PERIOD 2s FOR 30s

Event-Based:

ECA-triggers?(so called, actuation queries)

SELECT nodeid, tempFROM sensorsWHERE temp > thresholdOUTPUT ACTION power-on(nodeid)SAMPLE PERIOD 10s

IGERT-UIC-Sep09

(ECA)2 – Evolving and Context-Aware Event-Condition-Action

Active Databases Expert Systems (OPS5) Events Management

Events Notification Systems Continuous Queries ProcessingTriggers and Mobile Nodes TinyDB Why/What else?

Triggering EnginePostulate: In many dynamic settings, the need for detecting a particular event(s) and/or monitoring particularconditions arises only after: 1. certain events have been detected2. certain continuous conditions (do not) holdThe perception of “event” and“condition” can vary (especially indistributed settings)

IGERT-UIC-Sep09

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…

Evolving Reactive Behavior

WHEN an object is continuously_moving_towardsthe region R for more than 5 min., IF there are lessthen 10 jets in the base B1, then send alert_b tothe armored unit A1.

Air-Base B1

R

Also send alert_a to the infantry regimentI1, WHEN *that* object is closer than 3miles to R, IF all the marine units arefurther than 5 miles from R.

To send, or not to send…

IGERT-UIC-Sep09

A little “algorithmic-flavor”: continuously_moving_towards R for 6 min.

RB

C D

E

FA1. Generate the Voronoi diagram2. “Shoot-a-ray take-a-walk”3. Update the time_accumulator accordingly!!!

IGERT-UIC-Sep09

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’)

EventMoving-TowardsDetected

Distance Event Detected = CHILD OF THE ORIGINAL TRIGGER

No longer Moving-Towards

IGERT-UIC-Sep09

(ECA)2 – Evolving and Context-Aware Event-Condition-Action

When the body network of a resident signals readings which have been continuously approachinga threshold value for longer then 3 min.

If the number of on-site physicians < number ofendangered 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 = noON 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” detectedEvent “E_Traffic_Abnormality”

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(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 ...

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

Further nesting of children

IGERT-UIC-Sep09

(ECA)2 and the Meta-Triggers

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’)

OBSERVE:

It is very likely that Jets_Count(‘B1’,X,T)will be maintained by a remote server, for Whom a remote-request is nothing butan instantaneous query

But, then the “local site” (monitoring “moving_towards”) willhave to “ship” such queries upon every new detection…PLUS, it may miss some important changes at the airport in-betweenupdates (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!!!)(push mode!!!)

IGERT-UIC-Sep09

(ECA)2 and the Meta-Triggers

In general, initially we have a localTR1:ON E1IF CRemote AND CLocal

THEN A1

Meta-Trigger

TR1’:ON E1; (E-requested-remote; E-notification-from-remote)

AND CLocal

THEN A1

(input)

TR1-Remote:ON E-requested-remoteIF CContinuous

THEN A(E-notification-to-remote)

(output)

???

IGERT-UIC-Sep09

(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, …

Plus, the expressions which define the ramifications F1, F2, …, E1, E2, … suffice_for F/E

AUGMENTED WITH (ECA)2 TRIGGERS

F = facts (i.e., tuples)E = valid events

Action_Read_Radar induces Event_Location_Determined (NOTE: No Condition)

Event_Location_Determined, Time_Towards_Accumulator > 5 suffice_for E_Continuously_Moving _Towards

IGERT-UIC-Sep09

Hypothetical Reasoning

Basic “vehicles” are queries of the form:

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?

L after [A1,A2,…,An] at F1, F2, … E1, E2…

Design: experts from different domains involved

Deployment: status of the system and/or impact of modifications.

IGERT-UIC-Sep09

Hypothetical Reasoning

Example:

Formally:

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.

(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) ]

Sufficient defense resources = More than 5 F15s in the air-base B1 and more than 17 Type A1 Marksman in the infantry unit A1

IGERT-UIC-Sep09

TelosB – Proof of Concept…

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SID-net = Tool for hypothetical reasoning

150000x150000 ft2

(500 Mica2 Motes)

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Simulation Observations

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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 queriesUncertainty

Distributed (meta) indexing

IGERT-UIC-Sep09

Thank You!

IGERT-UIC-Sep09

(ECA)2 Additional Example

When a patient has been continuously moving towardsthe lake OR the perimeter fence for more then 5 min.If there is no nurse within 50 ft. from himNotify 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 lakeNotify 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) > 50THEN Alert(Security, T)

Fork:Consumed-by-Parent = no, Consume-parent = noON E_Moving_Along(1,Patient,T1, lake)IF Distance(Nurse,Patient,T1) > 100 AND Distance(Security,Patient,T1) > 100THEN Alert(Nurse, T1)

Event “E_Moving Towards”Event “E_Moving_Along”