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Spatial Programming using Smart Messages: Design and Implementation. Cristian Borcea , Chalermek Intanagonwiwat, Porlin Kang, Ulrich Kremer, and Liviu Iftode Department of Computer Science Rutgers University. Computers Go Outdoors, Embedded Everywhere in the Physical World.

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spatial programming using smart messages design and implementation

Spatial Programming using Smart Messages: Design and Implementation

Cristian Borcea, Chalermek Intanagonwiwat, Porlin Kang, Ulrich Kremer, and Liviu Iftode

Department of Computer Science

Rutgers University

computers go outdoors embedded everywhere in the physical world
Computers Go Outdoors, Embedded Everywhere in the Physical World

Cars collaborating

for a safer and

more fluid traffic

Distributed object

tracking over a large

geographical area

traditional indoor distributed computing
Traditional (Indoor) Distributed Computing
  • Computation is distributed for performance or fault tolerance
  • Relatively easy to program
    • Nodes are computationally equivalent
    • Networking is robust and has acceptable delays
    • Configuration is stable
outdoor distributed computing
Outdoor Distributed Computing
  • Computation is physically distributed
    • Nodes distributed across the physical space
    • Location-aware computing
  • Hard to program
    • Nodes are functionally heterogeneous and potentially mobile
    • Ad hoc wireless networks of embedded systems
    • Volatile configurations
example
Example

Mobile sprinkler

with temperature

sensor

Left Hill

Right Hill

Hot spot

  • “Water the hottest spot on the Left Hill”
  • Number and location of mobile sprinklers are unknown
  • Configuration is not stable over time
    • Sprinklers move
    • Temperature changes
traditional distributed computing does not work well outdoors
Traditional Distributed Computing Does Not Work Well Outdoors
  • End-to-end data transfers may hardly complete
  • Fixed address naming and routing (e.g., IP) are too rigid
  • Difficult to deploy new applications in existing networks
  • Outdoor distributed computing requires novel abstractions and programming models
    • How to write outdoor distributed applications?
    • How to deploy new applications in existing networks?
outline
Outline
  • Motivation
  • Spatial Programming (SP) Model
  • SP Implementation using Smart Messages
  • SP Application
  • Conclusions
traditional indoor programming
Traditional (Indoor) Programming
  • Programs access data through variables
  • Variables mapped to physical memory locations
  • Page Table and OS guarantee reference consistency
  • Access time has an (acceptable) upper bound

Program

Variable access

Virtual Address Space

Page Table + OS

Physical Memory

from indoor to outdoor computing
From Indoor to Outdoor Computing

Virtual Address Space

Space Region

Variables

Spatial References

Spatial references mapped

to systems embedded in

the physical space

Variables mapped to

physical memory

Reference consistency

?

?

Bounded access time

spatial programming sp at a glance
Spatial Programming (SP) at a Glance
  • Provides a virtual name space over outdoor networks of embedded systems
  • Embedded systems named by their locations and properties
  • Runtime system takes care of name resolution, reference consistency, and networking aspects
space regions
Space Regions

Hill = new Space({lat, long}, radius);

{lat,long}

radius

  • Virtual representation of a physical space
  • Similar to a virtual address space in a conventional

computer system

  • Defined statically or dynamically
spatial references
Spatial References

{Hill:robot[0]}

Hill

{Hill:robot[1]}

r7

r2

{Hill:motion[0]}

m5

  • Defined as {space:property} pairs
  • Virtual names for embedded systems
  • Similar to variables in conventional programming
  • Indexes used to distinguish among similar systems

in the same space region

reference consistency
Reference Consistency
  • At first access, a spatial reference is mapped to an embedded system located in the specified space
  • Mappings maintained in per-application Mapping Table (MT) – similar to a page table
  • Subsequent accesses to the same spatial reference will reach the same system (using MT) as long as it is located in the same space region

{space, property, index}

{unique_address, location}

reference consistency example
Reference Consistency Example

r2

r7

r5

Right Hill

Left Hill

{Left_Hill:robot[0]}.move = ON;

{Left_Hill:robot[0]}.move = OFF;

space casting
Space Casting

r7

Right Hill

Left Hill

{Left_Hill:robot[0]}

{Right_Hill:(Left_Hill:robot[0])}

bounding the access time
Bounding the Access Time
  • How to bound the time to access a spatial reference?
    • Systems may move, go out of space, or disappear
  • Solution: associate an explicit timeout with the spatial reference access

try{

{Hill:robot[0], timeout}.move = ON;

}catch(TimeoutException e){

// the programmer decides the next action

}

spatial programming example
Spatial Programming Example

Water the hottest spot on the Left Hill

Mobile sprinkler

with temperature

sensor

Left Hill

Right Hill

Hot spot

for(i=0; i<1000; i++)

try{

if ({Left_Hill:Hot[i], timeout}.temp > Max_temp)

Max_temp = {Left_Hill:Hot[i], timeout}.temp;

Max_id = i;

}catch(TimeoutException e)

break;

{Left_Hill:Hot[Max_id], timeout}.water = ON;

outline18
Outline
  • Motivation
  • Spatial Programming (SP) Model
  • SP Implementation using Smart Messages
  • SP Application
  • Conclusions
smart messages at a glance
Smart Messages at a Glance
  • Smart Message (SM)
    • User defined distributed application similar to a mobile agent
    • Executes on nodes of interest named by properties
    • Migrates between nodes of interest using self-routing
  • Self-Routing
    • Application-level routing executed at every node
    • Applications can change routing during execution
  • Cooperative Nodes
    • Execution environment (Virtual Machine)
    • Memory addressable by names (Tag Space)
    • Code cache
smart messages prototype
Smart Messages Prototype
  • Modified version of Sun’s Java K Virtual Machine
    • Small memory footprint (160KB)
  • SM and tag space primitives implemented inside virtual machine as native methods (efficiency)
  • Implemented I/O tags: GPS location, neighbor discovery, image capture, light sensor, system status
spatial programming implementation using smart messages
Spatial Programming Implementation Using Smart Messages
  • SP application translates into an SM
    • Spatial reference access translates into an SM migration to the mapped node
    • Embedded system properties: Tags
  • SM self-routes using geographical routing and content-based routing
  • Reference consistency
    • Unique addresses (stored in mapping table) are unique tags created at nodes
    • SM carries the mapping table
sp to sm translation example
SP to SM Translation: Example

Left Hill

Right Hill

Max_temp = {Left_Hill:Hot[1], timeout}.temp;

Spatial Reference Access

Mapping

Table

{Left_Hill,Hot,1}

{yU78GH5,location}

ret = migrate_geo(location, timeout);

if (ret == LocationUnreachable)

ret = migrate_tag(yU78GH5, timeout);

if ((ret == OK) && (location == Left_Hill))

return readTag(temp);

else throw TimeoutException

Smart Message

Code

sp application intrusion detection
SP Application: Intrusion Detection

Ad hoc network: HP iPAQs with 802.11 cards and GPS devices

user node

monitored

space

light sensor

camera node

regular node

Code Size breakdown for SM

(Application + SP Library)

Code Size breakdown for

SP library

conclusions
Conclusions
  • Spatial Programming makes outdoor distributed computing simple
    • Volatility, mobility, configuration dynamics, ad-hoc networking are hidden from programmer
  • Implementation on top of Smart Messages
    • Easy to deploy new applications in the network
    • Quick adaptation to highly dynamic network configurations
slide26

Thank you!

http://discolab.rutgers.edu/sp/