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University of Illinois at Urbana-Champaign OAI Alpha Experiences

University of Illinois at Urbana-Champaign OAI Alpha Experiences. Timothy W. Cole t-cole3@uiuc.edu Thomas G. Habing thabing@uiuc.edu Grainger Engineering Library Information Center 30 March 2001 http://dli.grainger.uiuc.edu/Publications/TWCole/LIT_OAIAlpha/. Context & Motivation.

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University of Illinois at Urbana-Champaign OAI Alpha Experiences

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  1. University of Illinois at Urbana-ChampaignOAI Alpha Experiences Timothy W. Colet-cole3@uiuc.edu Thomas G. Habingthabing@uiuc.edu Grainger Engineering Library Information Center 30 March 2001 http://dli.grainger.uiuc.edu/Publications/TWCole/LIT_OAIAlpha/

  2. Context & Motivation • Origins of Open Archives Initiative • E-Print Archives, Efficient Dissemination of Content • 1999 Santa Fe Convention • Metadata Key to Several UIUC Projects • DLI / D-Lib Test Suite • Digital Imaging & Multimedia Technology Initiative • Archives & Special Collections Finding Aids (EAD) • Kolb-Proust Archive (TEI) • Increasing Reliance on Digital Resources • Cross-Repository Discovery of Information Resources • Enhanced Sharing / Linking Between Resources OAI Metadata -- Univ. of Illinois at UC

  3. OAI Metadata Harvesting Protocol • Key Concepts • Repository, Record, Identifier, Datestamp, Set • How It Works • HTTP Request: Use GET or POST To Request Metadata • HTTP Response: XML or, if an error, HTTP Status-Code • Flow Control: resumptionToken and Retry Status-Code • Metadata Schemas: DC is required, but others allowed • Tools and Support • http://www.openarchives.org/ OAI Metadata -- Univ. of Illinois at UC

  4. OAI Metadata Harvesting Protocol • Verbs Identify: return administrative information about a repository ListMetadataFormats: return list of metadata formats supported by repository, or for specific record in repository ListSets: return a list of sets supported by the repository GetRecord: return 1 record given an identifier & format desired ListIdentifiers: return a list of record identifiers, optionally filtered by date or set ListRecords: return a list of records in a given metadata format, optionally filtered by date or set • Can’t Retrieve/Filter by Subject or Keyword OAI Metadata -- Univ. of Illinois at UC

  5. OAI Metadata Harvesting Protocol • Implementation Issues • Metadata Acquisition and Storage: Database or File System • Metadata Formats: Mapping to the Required OAI_DC format, plus optionally any other community-specific metadata formats • Set Definition -- Hierarchical or Overlapping • Flow Control -- How to Keep From Being Swamped • Limited Requirement to Maintain Inventory of Deleted Records (status=‘deleted’) • Access Control or User Authentication, if required • About Block Can Describe Conditions of Use OAI Metadata -- Univ. of Illinois at UC

  6. Metadata We Contributed (Alpha) • D-LIB Scientific / Technical Journal Articles • Articles from AIP & APS publications (~5,500 objects) • Metadata in XML (RDF, DC, Local Namespaces) • Implemented Access & Authorization Features • Added & Updated Metadata Records During Test • Digital Imaging and Media Technology Initiative • Digital Cultural Heritage Community -- Digitized Images for Elementary Grades Curricula (~500 objects) • Metadata in Flat Database Structure • Planned Future Additions • Digitized Historical Aerial Photos of Illinois • EAD Finding Aids for Manuscript Archive Collections OAI Metadata -- Univ. of Illinois at UC

  7. Computing Environment • MS Windows NT 4.0 Operating System • MS Internet Information Server 4.0 • Active Server Pages (VBScript & JScript) • MS SQL Server 7 and MS Access 97 • D-Lib XML Data Uploaded Using Visual Basic & MSXML Parser / DOM Implementation • Future Plans • Windows 2000, IIS 5, SQL & Access 2000 • XML Extensions for MS SQL Server OAI Metadata -- Univ. of Illinois at UC

  8. Assumptions / Groundrules • Each Object Member of 1 and Only 1 Set Hierarchy • Flow-Control Exclusively Using resumptionTokens • Non-ASCII Characters May Be Included • UTF-8 and � hexadecimal character references • Not Investigated During Alpha Testing • Mechanisms to Maintain Server-Side Statefulness • Redirection Using HTTP Headers • Status=‘Deleted’ (Attribute of recordType) • Alternative Metadata Formats (e.g., DCQ or Formats Allowing Embedded Markup from XHTML Namespace) OAI Metadata -- Univ. of Illinois at UC

  9. http://bolder.grainger.uiuc.edu/dlibmeta/oai.asp?verb=GetRecord&identifier=oai:idli:70739&metadataPrefix=oai_dchttp://bolder.grainger.uiuc.edu/dlibmeta/oai.asp?verb=GetRecord&identifier=oai:idli:70739&metadataPrefix=oai_dc OAI Metadata -- Univ. of Illinois at UC

  10. http://bolder.grainger.uiuc.edu/oaisimple/oai.asp?verb=GetRecord&identifier=oai:uiuc:184500&metadataPrefix=oai_dchttp://bolder.grainger.uiuc.edu/oaisimple/oai.asp?verb=GetRecord&identifier=oai:uiuc:184500&metadataPrefix=oai_dc OAI Metadata -- Univ. of Illinois at UC

  11. System Architecture • Metadata Maintained in Relational DB • Root table & secondary tables (e.g., 1 each DC category) • Additional tables for set descriptions & supported schemas • Stored Procedures Map DB Fields to Schema ElementsDe-couples Database Schema from Metadata Schema(s) • OAI Responses Built Dynamically • Use ASP To Query DB & Build Response Each OAI Verb becomes a Case Statement XML Syntax & Semantics Explicitly Coded in ASP HTTP Errors Constructed Using ASP Built-in Objects Authentication & Access Controls in global.asa Maintained Separate Log Files OAI Metadata -- Univ. of Illinois at UC

  12. About object_id date_stamp sets DC_Creator object_id creator DC_Title object_id title DC_Subject object_id subject scheme Database Schema 1:n 1:n OAI Metadata -- Univ. of Illinois at UC

  13. Evaluative Comments • Given Metadata, Minimal Effort to Implement OAI • 2 to 4 Weeks to Design DB & Upload Data • 2 to 4 Weeks to Implement OAI Provider Service • Generic, Modular Technology for Sharing Metadata • Usable for Both Vertical & Cross-Domain Applications • Boon to Institutions (like libraries) that Have Multiplicity of Diverse Collections • More Work to Do on Harvest Service Applications • How Powerful is Search Against LCD Metadata Schema • Cross-Schema Mapping Issues Still Remain • Local Linking & Presentation Issues Remain OAI Metadata -- Univ. of Illinois at UC

  14. Possible Future Work • Alternative System Architectures • Single Table DB Schema for All Metadata Content • File-System Based Metadata Storage Approach • Exploit MS XML Front-End to SQL Server • Turnkey OAI Provider Service Applications • E.g., Generic ASP with Template MS Access Database • OAI Metadata Brokerage Services • OAI Metadata Harvesting Service for Manuscript Archives & Cultural Heritage Information OAI Metadata -- Univ. of Illinois at UC

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