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The OCKHAM / NSDLDigital Library Services Registry

A Distributed Approach

To Enable End-to-End

Digital Service Resolution

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emory ▪ notre dame ▪ oregon state ▪ virginia tech

•Funded by the National Science Foundation

•National Science Digital Library Program

•2 Year Project Funding

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Goals1. Create a Registry for all possible Digital Library Services2. Enable End-to-End Digital Library Service Resolving

Sub-Goals

1. Ensure DLSR is Scalable and Redundant2. Ensure Manageability of DLSR is Scalable 3. Use Existing Standards and Technologies

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Use of the DLSR

1. Library Portal Use Case2. Metasearch Use Case3. Personal Digital Library

3 Examples

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Distributed DLSR

•The OCKHAM/NSDL DLSR is Distributed•Many nodes over the network•Scalability•Redundancy

•Approach in part based on DNS model

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A Brief History of DNS

•Hosts.txt file (later just hosts)•ARPAnet started with centralized management

•Inter-NIC•Eventually, a more manageable approach was needed•Current Distributed DNS System was created

•Allows De-centralized administration•Hierarchical design

•Simplifies management•Reduces bandwith, bottlenecks•Reduces duplicate name issue (i.e. .edu, .com, etc.)

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Distributed DLSR

•Reasoning much the same as DNS•Similarities and Differences

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emory ▪ notre dame ▪ oregon state ▪ virginia tech

emory ▪ notre dame ▪ oregon state ▪ virginia tech

Data LayerRelational Db & OJB• Synchronized• Database

Interchangeability• Ease of development

Lucene• Fast indexing• “on the fly” indexing• Flexible query engine

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Interface LayerCurrent Interfaces• Struts powered J2ee

interface • OAICat - OAI-PMH 2.0

Future Interfaces• SRU/W • Z39.50• OpenURL

Output Formats• Html• XML

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Clients• Web browser• OAI-PMH • Z39.50• Any web enabled

application.

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Network Layer• JXTA provides low level

network functionality– Peer identification and

discovery– Transport layer

• PeerManager provides modular application level functionality

– Load Management– Client/Server Modules

• Main Registry Modules– URL Server– Harvester Client

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Using OAI For Propagating Data

• A peer can query any other peer and receive an incremental update

• Queries are based on the latest record modification date for the peer’s local copy of the set

• Subsequent queries will use the new latest record modification date

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Hierarchal Network Topology

Topology Requirements• Data must propagate to all

peers• Compensation for inherent

instability of P2P networks• Scalable structure• Low overhead• DNS for Digital Library

Services

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Put the pieces together

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OCKHAM Future

•Expand the DLSR Community and Use•Explore and build DLSR-aware tools and services•Prototype semi-automated creation of DL’s

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Further Information

OCKHAM Website – http://ockham.org

Martin Halbert, Emory – mhalber@emory.edu

Jeremy Frumkin, Oregon State University – jeremy.frumkin@oregonstate.edu