Service Discovery in Ubiquitous and Pervasive Environments

1
Service Discovery in Ubiquitous and Pervasive
Environments

• Presented by Knarig Arabshian
• PhD candidacy exam
• October 26, 2004

2
Overview

• Introduction
• History of service discovery, challenges
• Components
• Description, distribution, query
• Existing systems
• Mainstream, ad-hoc, location aware, semantic,
  Internet-scale

http//www.cs.columbia.edu/knarig/candidacy/candi
dacyList.html
3
What is service discovery?
Service vs resource discovery
4
History of resource discovery
6 A comparison of internet resource discovery
approaches, 1992 7 Resource location protocol,
1983
5
Motivationfor new service discovery protocols
Static resource information (whois, RLP, X.500)
Automatic discovery of LAN network services (SLP,
Jini, UPnP)

• Automatic
• Automatically announce or register service
  instead of manually entering information.
• LAN services
• Printer, FAX machine,

8 Protocols for service discovery in dynamic
and mobile networks, IJCR (Journal), 2002
6
Motivationfor new service discovery protocols
Static resource information (whois, RLP, X.500)
Automatic discovery of LAN network services (SLP,
Jini, UPnP)
Internet scale discovery (INS/Twine, Ninja)

• Wide-area service discovery
• Multiple attributes
• Auto configured and rapid availability
• Automated discovery without user input
• Policy support by agent
• Scalable

7
Motivationfor new service discovery protocols

• Pervasive computing
• User intent
• Client thickness
• Cyber foraging (living off the land)
• Context awareness
• Proactive vs transparent
• Ad hoc networks

Static resource information (whois, RLP, X.500)

• Me-services
• Personal and pervasive
• Semantic service discovery
• Dynamic service composition
• Distributed trust management
• Profile driven management

Automatic discovery of LAN network services (SLP,
Jini, UPnP)
Internet scale discovery (INS/Twine, Ninja,
CoolTown)

• Semantic web
• Express meaning
• Knowledge representation using ontologies
• Improving accuracy of web search
• Agents exchange ontology information to perform
  service discovery

Ad hoc discovery without infrastructure (Konark,
DEAPSpace)
Location aware discovery (Agents2Go, Splendor)
Semantic service discovery (Ronin, DReggie)
1 The semantic web, Scientific American,
2001 2 Pervasive computing vision and
challenges, IEEE personal communications,
2001 4 Me-services a framework for secure and
personalized discovery, 2002
8
Components

• Directory repository
• Centralized
• Distributed
• Hierarchical
• Structured P2P
• Ad hoc
• Service description
• Attribute/value
• Tree-like
• XML
• Ontologies (DAML)

Consumer
Provider
Directory
9
Components

• Announcement
• Register
• Multicast/broadcast
• Query/Service Access
• Syntax
• Ontology
• Programming language dependency

Consumer
Provider
Directory
References for mainstream protocols 9 The
Service Location Protocol, IEEE Internet
Computing, 1999 11 Jini architecture
specification, Sun Microsystems, 2003 12
Understanding Universal Plug and Play white
paper, Microsoft, 2000 13 Specification of the
Bluetooth system, Bluetooth 14 Salutation
architecture specification version 2.1, The
Salutation Consortium, 1999
10
Mainstream protocols
11
Mainstream protocols
12
More protocolsmSLP mesh-enhanced SLP

• Fully-meshed peering DA architecture with one or
  more scopes in common
• Reliability
• Scalability
• Backward Compatibility- extends DA Advertisement
  with a mesh-enhanced attribute

10 mSLP mesh enhanced SLP, ICCCN, 2000
13
More protocolsUDDI Universal Description,
Discovery and Integration

• UDDI specifications and schemas used to build
  discovery services on Internet
• Provide consistent publishing interface
• Allow programmatic discovery of services
• Who Sun, IBM, Microsoft partnership

15 UDDI technical white paper, 2000
14
More ProtocolsUDDI Universal Description,
Discovery and Integration
Consumers access services by using the
Programmers API built on SOAP
Services described in XML and published using
Publishers API
Business registry contains yellow, white, green
pages
15
Design for ad hoc networks

• No central directory service
• Limited use of network/device resources
• Reliability
• Pervasive
• Distributed

Konark DeapSpace GSD Allia
16
Design for ad hoc networks

• Main entities
• Node acts as clientserver
• Service announcement
• Flooding
• On device join
• Periodically, delta announcement (Konark)
• Slotted (DEAPSpace uses slottedperiodic)
• Cache advertisements
• TTL

17
Design for ad hoc networks

• Service description
• What is described?
• service name, type, attribute, keywords,
  properties and functions
• Service hierarchy - tree like structure (Konark,
  GSD)
• Interface format, e.g., function prototype.
• How is it described and stored?
• WSDL file (Konark)
• Data structures similar to ASN.1 (DEAPSpace)
• Encoder/decoder
• Ontology DAMLOIL (GSD)

18
Design for ad hoc networks

• Access to the service
• RPC
• SOAP/HTTP (Konark)
• Specific Interface, e.g., function prototype
• Encoder/decoder (DEAPSpace)
• Query formation
• Path based or syntax based
• Request routing
• Policy based (Allia)
• Group based (GSD)

19
Contributions
17 Konark a service discovery and delivery
protocol for ad hoc networks, WCNC, 2003 18
DEAPspace transient ad hoc networking of
pervasive devices, Computer Networks, 2001 19
GSD a novel group-based service discovery for
MANETS, MWCN, 2002 20 Allia alliance-based
service discovery for ad-hoc environments, WMC,
2002
20
Design for semantic ontologies
Find me the best cab service

• Use of semantic ontologies
• Inexact/exact querying
• More powerful reasoning engines and AI tools
• Enhancing current service location protocols

Ronin Agent Framework DReggie
21
Contributions

• Ronin Agent Framework
• Built on top of Jini
• Jini Prolog engine
• Agent-oriented development
• Java classes and interfaces
• printing service, restaurant service
• Communicate with other agents using Agent
  Communication Language
• Agent deputy
• Mediates agent communication
• Represents owner agent in the network
• Located in the Jini Lookup Service

• Dreggie for M-commerce
• Enhance Jini
• Matching mechanism of Jinis LookupService
• Prolog reasoning engine used for matching
• Service registration along with interface
  registration
• Services register with DAML description and
  interface
• DAML gives hierarchical description of services

21 Dynamic service discovery for mobile
computing, BSJCC (Journal), 2001 22 Dreggie
semantic service discovery for M-commerce
applications, 2001
22
Location-aware service discovery

• Where is the closest Italian restaurant
• to me?
• Location sensing
• Nomadic users
• Handy devices

CoolTown, Splendor, Agents2Go
23
CoolTown

• Every service (e.g., printer) has a web server,
  and a tag.
• Users walk in and receive URL from tag beacons
• Connect to the URL which describes the service
  and can invokes it
• Place manager maintains resources in a place,
  with web interface (HTML and XML)
• Resources can be grouped.
• Also acts as a resolver for some places

24
Splendor

• Tag-based location aware
• Tag label location and people
• Proxies
• Enhanced security
• Service management (registration, security)

Trusted servers managing services
Bootstrapping using multicast
25
Agents2Go
PalmApp (with CDPD modem)
Cell tower
Location identified by cell tower id
register
Restaurant agent or other services
Initial query form
User query
Brokers
Area 2
User query
Locator
Area 3
Maps geographic area to broker
Agents2Go Server
26
Contributions

• Attach web URL to services and periodically
  broadcast (CoolTown)
• Intermediate trusted proxy for security and
  service management (Splendor)
• Localized brokers store services in the location
  and are mapped to based on the user location
  (Agent2Go)

23 Agents2Go an infrastructure for
location-dependent service discovery, 2001 24
Splendor a secure, private, location-aware
service discovery protocol, 2003 25 A web-based
nomadic computing system, Computer Networks, 2001
27
Internet-scale discovery

• Construct scalable, robust services
• Huge throughput demands and availability
• Interoperability
• Efficiency
• Fault tolerance

INS/Twine, Ninja/SDS, WSPDS
28
INS/Twine
root

• Uses Chord
• structured peer to peer system
• Lookup in Log(N)
• Service Propagation
• Resource state changes, update is propagated
• Periodic refreshing of resource information
• edge resolvers attached to clients update
  frequently
• Internal resolvers infrequently

subject
res
resolver
camera
traffic
model
man
AModel
ACompany
Resource is a camera, manufactured by ACompany
and filming traffic.
StrandMapper Hash(strand)
Distributed hash table (Chord). KeyRouter maps to
Chord.
30 INS/Twine a scalable p2p architecture for
intentional resource discovery, 2002
29
Ninja

• Secure Service Discovery Service (SDS)
• Uses XML to encode service descriptions
• Certificate Authority and Capability Managers for
  security
• Servers dynamically organize themselves into
  hierarchies for scalability
• Filters query upwards to avoid overloading one
  node (Bloom filter)

Services running on clusters of workstations
Distributed data structures
A chain across proxies and bases to find better
service
Stateless and soft-state proxy
Heterogeneous devices and sensors
28 The ninja architecture for robust
Internet-scale systems and services, JCN,
2001 27 An architecture for a secure service
discovery service, MobiCom, 1999
30
Multi-tier ubiquitous service discovery protocol
Global Services Registry-gateway to global network

• Context attributes provided by services
• Distance to server
• Server load
• Service channel
• Attribute-value pair service description
• Localized Service Propagation
• propagate upward with attenuation factor of
  service attributes
• Query Routing
• Overlay hierarchy

Brokering Agent-recommends appropriate service
Global Services
26 A multi-tier ubiquitous service discovery
protocol, Mobisys, 2003
Domain Hierarchy
31
WSPDS Web Services P2P Discovery Service

• Servent Server/Client
• DAML ontology for service description
• Querical data network
• Probabilistic flooding
• Each node defined by content
• Node links to other nodes of smiliar content
• Semantic matching algorithm used to choose
  neighbor

29 WSPDS web services p2p discovery service,
ISWS, 2004
32
Contributions

• INS/Twine structured P2P lookup on strands
• Ninja/SDS query filtering and service
  aggregation
• Multi-tier Ubiquitous SDP context attributes,
  hierarchical, localized service propagation
• WSPDS QDN, DAML for service description

33
Conclusions

• Service discovery for different scenarios in
  ubiquitous and pervasive environments ad-hoc,
  location-aware, semantic and Internet-scale, and
  combinations of these
• Tackle problems in service distribution, query
  and description
• Not much work done in semantic service discovery

34
References

• T. Berners-Lee, J. Hendler, and O. Lassila, The
  Semantic Web, Scientific American , May 2001
• M. Satyanarayanan, Pervasive Computing Vision
  and Challenges, IEEE Personal Communications ,
  August 2001.
• M. Weiser, The computer for the twenty-first
  century Scientific American, pp 94-103, September
  1992
• Anupam Joshi, Tim Finin, and Yelena Yesha,
  Me-Services A Framework for Secure and
  Personalized Discovery, Composition and
  Management of Services in Pervasive Environments,
  in Web Services, E-Business, and the Semantic
  Web, C. Bussler, R. Hull, S. McIlraith, M.E.
  Orlowska, B. Pernici, J. Yang (Eds.), LNCS 2512,
  p. 248 ff., Springer, ISBN3540001980, December
  2002
• J. Rosenberg, E. Guttman, R. Moats, H.
  Schulzrinne, WASRV Architectural Principles
  Internet Draft, Internet Engineering Task Force,
  Feb. 1998. Work in progress.
• Michael F. Schwartz, Alan Emtage, Brewster Kahle,
  and B. Clifford Newman. A comparison of internet
  resource discovery approaches, Computing Systems,
  5(4)466-493, Fall 1992.
• M. Accetta, Resource Location Protocol RFC 887,
  Internet Engineering Task Force, December 1983.
• C. Lee, S. Helal, Protocols for Service Discovery
  in Dynamic and Mobile Networks, International
  Journal of Computer Research, Volume 11, pp 1-12,
  2002
• Erik Guttman, The Service Location Protocol, IEEE
  Internet Computing July 1999.
• Weibin Zhao, Henning Schulzrinne and Erik
  Guttman, "mSLP - Mesh-enhanced Service Location
  Protocol", International Conference on Computer
  Communications and Networks (ICCCN'00), October,
  2000.
• Jini Architecture Specification, Sun
  Microsystems, June 2003
• Understanding Universal Plug and Play White
  Paper, Microsoft Corporation, June 2000.
• Specification of the Bluetooth System, Bluetooth
  (www.bluetooth.org), pp 113-156
• Salutation Architecture Specification Version
  2.1, The Salutation Consortium, 1999
• UDDI Technical White Paper, UDDI (Universal
  Description, Discovery and Integration),
  September 2000.
• A. Gulbrandsen, P. Vixie, L. Esibov, A DNS RR for
  specifying the location of services (DNS SRV) RFC
  2782, Internet Engineering Task Force, February
  2000.

35
References

• S. Helal, N. Desai, V. Verma and C. Lee,
  Konark--A Service Discovery and Delivery Protocol
  for Ad-hoc Networks, Proceedings of the Third
  IEEE Conference on Wireless Communication
  Networks (WCNC), New Orleans, March 2003.
• R. Hermann, D. Husemann, M. Moser, M. Nidd, C.
  Rohner, A. Schade, DEAPspace--Transient ad hoc
  networking of pervasive devices, Computer
  Networks Volume 35 pp 411-428, 2001
• D. Chakraborty, A. Joshi, , GSD A Novel
  Group-based Service Discovery Protocol for
  MANETS, 4th IEEE Conference on Mobile and
  Wireless Communications Networks (MWCN 2002).
  Stockholm. Sweden. September. 2002
• Olga Ratsimor, Dipanjan Chakraborty, Sovrin
  Tolia, Deepali Kushraj, Anugeetha Kunjithapatham,
  Gaurav Gupta, Anupam Joshi, Timothy Finin, Allia
  Alliance-based Service Discovery for Ad-Hoc
  Environments, Second ACM International Workshop
  on Mobile Commerce, in conjunction with Mobicom
  2002, Sep 28, 2002, Atlanta GA, USA
• H. Chen, A. Joshi, T. Finin. Dynamic Service
  Discovery for Mobile Computing Intelligent
  Agents Meet Jini in the Aether, Baltzer Science
  Journal on Cluster Computing, Vol. 4, No. 4,
  March 2001
• D. Chakraborty, F. Perich, S. Avancha, and A.
  Joshi. DReggie Semantic Service Discovery for
  M-Commerce Applications In Workshop on Reliable
  and Secure Applications in Mobile Environment,
  Symposium on Reliable Distributed Systems,
  October 2001.
• O. Ratsimor, V. Korolev, A. Joshi, T. Finin.
  Agents2Go An Infrastructure for
  Location-Dependent Service Discovery in The
  Mobile Electronic Commerce Environment ACM Mobile
  Commerce Workshop, July, 2001
• F. Zhu, M. Mutka, and L. Ni, Splendor A Secure,
  Private, and Location-aware Service Discovery
  Protocol Supporting Mobile Services 1st IEEE
  Annual Conference on Pervasive Computing and
  Communications, IEEE Computer Society Press, Fort
  Worth, Texas, 2003
• T. Kindberg and J. Barton, A Web-based nomadic
  computing system, Computer Networks, Esevier. Vol
  35, No. 4, March 2001, 443-456
• C. Lee and A. Helal, A Multi-tier Ubiquitous
  Service Discovery Protocol First ACM
  International Conference on Mobile Systems and
  Applications (Mobisys), May 2003
• S.E. Czerwinski, B. Zhao, T. Hodes, A. Joseph,
  and R. Katz, An Architecture for a Secure Service
  Discovery Service, Fifth Annual International
  Conference on Mobile Computing and Networks
  (MobiCom '99), Seattle, WA, August 1999, pp.
  24-35
• S. D. Gribble, M. Welsh, R. von Behren, E. A.
  Brewer, D. Culler, N. Borisov, S. Czerwinski, R.
  Gummadi, J. Hill, A. Joseph, R. H. Katz, Z. M.
  Mao, S. Ross, and B. Zhao, The Ninja architecture
  for robust Internet-scale systems and services,
  Journal of Computer Networks, vol. 35, no. 4,
  March 2001.
• Farnoush Banaei-Kashani, Ching-Chien Chen, Cyrus
  Shahabi, WSPDS Web Services Peer-to-peer
  Discovery Service , International Symposium on
  Web Services and Applications(ISWS'04) , Las
  Vegas, Nevada, USA, June, 2004
• M. Balazinska, H. Balakrishnan, D. Karger,
  INS/Twine A Scalable Peer-to-Peer Architecture
  for Intentional Resource Discovery, International
  Conference on Pervasive Computing August 2002