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Danmarks Tekniske Videncenter / Technical Knowledge Center of Denmark
Danmarks Tekniske Universitet / Technical University of Denmark
DORSDL Workshop, 21 September 2006
Development of Services in the Fedora Service Framework
by Gert Schmeltz [email protected]
2DORSDL Workshop, 21 September 2006
Development of Services in the Fedora Service Framework
• Contents– The Fedora Service Framework– The Fedora Generic Search Service– Considerations about a Peer-to-Peer Service for Fedora– Conclusion
3DORSDL Workshop, 21 September 2006
The Fedora Service Framework
• Services are stand-alone web applications that run independently of the Fedora repository
• Two main benefits to the service framework approach:
– allows new functionality to be added as atomic, modular services that can interact with Fedora repositories, yet not be part of the repository,
– makes co-development of new services for Fedora easier since each service can be independently developed and plugged into the framework.
Flexible Extensible Digital Object Repository Architecture
• Powerful digital object model
• Extensible metadata management
• Expressive inter-object relationships
4DORSDL Workshop, 21 September 2006
The Fedora Service Framework
• Fedora Object XML (FOXML) is a simple XML format that directly expresses the Fedora digital object model
5DORSDL Workshop, 21 September 2006
Development of Services in the Fedora Service Framework
• The Fedora Generic Search Service– Background
• The DEF-XWS project• Zebra at work• Lucene in action
– Approach and requirements– Current prototype (fedoragsearch)– Architectural snapshots– Configuration and customization– Further work
– The work is funded by DEFF, Denmark's Electronic Research Library.
6DORSDL Workshop, 21 September 2006
OAIManager
Full set
Sub set
Librarian
DEF Portal User
OAIHarvester
Open Archives Initiative Data Providers
MYSQL
Z39.50
OAI-PMH
Eprint Service Provider
Zebraserve
r
Web UIw/
Z39.50
InfoNetUserZebra
server
Web UIw/
Z39.50
EXPORT
Fedora server
Zebra server
Full text retrieval
Batch ingest
EXPORT
AppXYZ User
DEF-XWS Eprints User
DEF-XWS Eprints User
SOAP/REST
Web UIw/SOAP
javaWeb UIw/REST
php
AppXYZw/SOAP
perl
Background - DEF-XWS Eprints
7DORSDL Workshop, 21 September 2006
• Purpose achieved– Fedora hands-on and experience– web services hands-on and experience– DEF-XWS Eprints available from web services
• http://defxws.cvt.dk:8082/fedora/access/soap?wsdl• http://defxws.cvt.dk:8082/fedora/accessDEF-XWS/soap?wsdl• and to applications combining many web services
• Lesson– Do not override field search, – provide generic search service instead ...
Background - DEF-XWS Eprints
8DORSDL Workshop, 21 September 2006
Zebra at work
Features• Zebra is provided as open source by Index Data.• Written in portable C, so it runs on most Unix-like
systems as well as Windows. • Modules zebraidx and zebrasrv• Searching supports a combination of boolean queries,
relevance-ranking, truncation, masking, full regular expression matching and "approximate matching" (eg. spelling mistakes).
• Z39.50 protocol support, recently also SRW/SRU and CQL
• Configurable to understand many input formats... SGML, XML, ISO2709 (MARC), raw text.
• Arbitrarily complex records. • Robust updating - records can be added and deleted
“on the fly”.• Very large databases: logical files can be automatically
partitioned over multiple disks.
9DORSDL Workshop, 21 September 2006
”Lucene in Action”
Figure 1.5 A typical application integration with Lucene
Document
Field
dc.title:"Information retrieval" ANDdc.creator:Staples
http://lucene.apache.org/java/docs/queryparsersyntax.html
10DORSDL Workshop, 21 September 2006
Approach and Requirements
• Do iterations of requirements analysis and prototype development
• allow various indexing-and-search engines to be configured or plugged in, initially Lucene and Zebra
• implement as a webapp within the Fedora Service Framework
• allow indexing of, and search in, all information in FOXML records for FedoraObjects, including full texts in datastreams and disseminator results
• define interface for a set of operations, provide REST and SOAP access
• basic operations:– updateIndex - indexing the contents of the Fedora repository
– gfindObjects - search similar to Fedora findObjects
• secondary operations:– browseIndex - browsing terms in a given index.
– getRepositoryInfo - describing the properties of a repository
– getIndexInfo - describing the properties of an index
• allow multiple repositories to be indexed in one and the same index
• allow multiple indexes to be generated from one repository
11DORSDL Workshop, 21 September 2006
Current prototype - updateIndex<foxml:digitalObject … PID="demo:21"> <foxml:objectProperties> <foxml:property NAME="http://www.w3.org/1999/02/22-rdf-syntax-ns#type" VALUE="FedoraObject"/> <foxml:property NAME="info:fedora/fedora-system:def/model#state" VALUE="Active"/> <foxml:property NAME="info:fedora/fedora-system:def/model#label" VALUE="Sample Document Object (FO to PDF)"/> <foxml:property NAME="info:fedora/fedora-system:def/model#contentModel" VALUE="FO_TO_PDFDOC"/> </foxml:objectProperties> … <foxml:datastream ID="DC" STATE="A" CONTROL_GROUP="X" VERSIONABLE="true"> <foxml:datastreamVersion ID="DC1.0" LABEL="Dublin Core for the Document object" CREATED="2006-05-16T10:23:48.376Z" MIMETYPE="text/xml" SIZE="606"> <foxml:xmlContent><oai_dc:dc xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:dc="http://purl.org/dc/elements/1.1/"> <dc:title>Advanced FO Sample from Apache FOP Distribution</dc:title> <dc:creator>Apache Group</dc:creator></oai_dc:dc> </foxml:xmlContent> </foxml:datastreamVersion> </foxml:datastream></foxml:digitalObject>
<IndexDocument … > <IndexField IFname="PID“ … >demo:21</IndexField> <IndexField IFname="property.type“ … >FedoraObject</IndexField> <IndexField IFname="property.state“ … >Active</IndexField> <IndexField IFname="property.contentModel“ … >FO_TO_PDFDOC</IndexField>
<IndexField IFname="dc.title">Advanced FO Sample …</IndexField> <IndexField IFname="dc.creator">Apache Group</IndexField> <IndexField index="TOKENIZED" dsId="DS1" IFname="DS1.text"/> </IndexDocument>
transformation
17DORSDL Workshop, 21 September 2006
Architectural snapshots - basic - fedoragsearch
• Contents– Lucene– Zebra– fedoragsearch
• REST demo• architecture• installation and configuration• further customizations
19DORSDL Workshop, 21 September 2006
Configuration and customizationConfiguration examples:
fedoragsearch.properties- soapBase = http://HOSTPORT/fedoragsearch/services- repositoryNames = REPOSNAMES- indexNames = INDEXNAMES- mimeTypes = MIMETYPES
INDEXNAME/index.properties- operationsImpl = dk.defxws.fgslucene.OperationsImpl- defaultQueryFields = dc.description dc.title
REPOSNAME/repository.properties- soapBase = http://FEDORAHOSTPORT/fedora/services- fedoraObjectDir = FEDORAOBJECTDIR
Customization examples:
demoFoxmlToLucene.xslt
<IndexField IFname="DS2.text" dsId="DS2" index="TOKENIZED" store="YES" termVector="NO"></IndexField>
demoGfindObjectsToHtml.xslt
<script …AJAX-script … /><h2>gfindObjects</h2><form method="get" action="rest">
Implement plugin for XyzEngine
20DORSDL Workshop, 21 September 2006
Further work
• From prototype to production version• Clean up• Give access• Make better Exceptions and error messages• Handle XACML• Notification mechanism• javaDoc• Junit test cases• Test on various platforms• Documentation• Ensuring that we obtain the same high quality as the Fedora code
itself has
• Takeover by core development team
• Contributions from Fedora community
21DORSDL Workshop, 21 September 2006
Development of Services in the Fedora Service Framework
• Considerationsabout a Peer-to-Peer Service for Fedora
1. The Background: Alvis utilization activities2. The EU project: Alvis - Superpeer Semantic Search
Engine3. Analysis of alternatives4. Design of a Peer-to-Peer service for Fedora
22DORSDL Workshop, 21 September 2006
The Background:Alvis utilization activities
• The Alvis project is developing an open source prototype of a distributed, semantic-based search engine.
• An important consideration in the Alvis project has been how to utilize Alvis results in the Digital Library context.
• Therefore, a test case is established with the purpose to utilize Alvis results in the context of the Fedora repository system
(the assumption is that the experience and some principles will be applicable to other digital library systems)
• The test plan for this test case has the following steps:
1. Analysis• Alternative 1: a document enrichment service• Alternative 2: a peer-to-peer service
2. Design of a peer-to-peer service for Fedora, so that Fedora may act as an Alvis superpeer
3. Involving the Fedora developer and user community 4. Implementation of the service 5. Evaluation of uses of the service
23DORSDL Workshop, 21 September 2006
The Alvis EU project
The initial tasks
• research in the design, use and interoperability of topic-specific search engines
• development of an open-source prototype of a distributed, semantic-based search engine
• building on content through automatic analysis of free text
• advancing peer-to-peer technology
24DORSDL Workshop, 21 September 2006
The Alvis EU project
• input system can include a crawler, an RSS reader, XML database extraction, etc.
• document system does routine processing on documents prior to entry to the runtime system, such as tagging named entities.
• maintenance system does processing at the full document collection level to update linguistic and semantic resources used in the document system.
• superpeer runs the search engine at a node and provides the user interface. This represents an individual, possibly topic specific search engine.
• p2p system provides a network-wide interface to a set of individual search engines using P2P.
Document enrichment service
•semi-automatic tagging with semantic knowledge
Peer-to-Peer service•network-wide search
Peer-to-peer (From Wikipedia, the free encyclopedia)
•A peer-to-peer (or P2P) computer network is a network that relies primarily on the computing power and bandwidth of the participants in the network rather than concentrating it in a relatively low number of servers.•The P2P overlay network consists of all the participating peers as its nodes and has links between any two nodes that know each other•Structured P2P networks overcome the limitations of unstructured networks by maintaining a Distributed Hash Table (DHT) and by allowing each peer to be responsible for a specific part of the content in the network.
25DORSDL Workshop, 21 September 2006
WP9User
interface
WP7Crawler
WP5Linguisticanalysis
WP2Relevance
analysis
WP3Indexingengine
WP6Resourceacquisition
Acq
uisi
tion
form
at
Ling
uist
ic f
orm
at
Rel
evan
ce f
orm
at SRU/Z39.50
WP4Peer-
to-peer
WP8
Chinese contributionCrawler, linguistic analysis and relevance
analysis
Analysis: Document enrichment service
27DORSDL Workshop, 21 September 2006
Analysis: Document enrichment service
Functionality as a Fedora service
• Topic-specific crawling based on subject hierarchies• Natural language analysis of content• Entity recognition• Classification of content• Addition of synonyms• Topic specific scores for customised rankings
Too many partners/modules/subsystems involvedUsages of enrichment not clarified
28DORSDL Workshop, 21 September 2006
The initial vision
•A set of heterogeneous servers connected into a search network
•Each one is wrapped suitably, so as to act as Alvis Search Peers
•In this view, Fedora repositories may be wrapped as well.
wrapper
Analysis: Peer-to-Peer service
29DORSDL Workshop, 21 September 2006
Design: alvisp2p service
• The alvisp2p service shall implement the interfaces IndexingQuery and Retrieval for interacting with the P2P system, and
• implement the necessary operations for interacting with the core Fedora repository service.
• Seen from the ALVIS view point we will then have a thin superpeer,
• seen from the Fedora view point we will have a Peer-to-Peer service.
30DORSDL Workshop, 21 September 2006
Development of Services in the Fedora Service Framework
• Conclusion
– Two examples of services illustrating the issues in developing services for the Fedora Service Framework• Interaction with Fedora• Reuse from Fedora• Security
– A promising development approach for Fedora– Promising in general for Digital Object Repository
Systems in Digital Libraries?
Thank you
31DORSDL Workshop, 21 September 2006
For more information
• A Peer-to-Peer Architecture for Information Retrieval Across Digital Library Collections, Technical report LSIR-REPORT-2006-005, March 2006.
• Report on abstract model and P2P protocols, ALVIS Deliverable 4.1, 2006. • Beyond term indexing: A P2P framework for Web information retrieval,
submitted to thr Informatica journal, December 2005.• Building a peer-to-peer full-text Web search engine with highly discriminative
keys, Technical report LSIR-REPORT-2005-011, November 2005. • Using a layered Markov model for distributed web rank computation, ICDCS
2005, Columbus, Ohio, U.S.A., June 2005.• Towards A Common Framework for Peer-to-Peer Web Retrieval, Book
Chapter of From Integrated Publication and Information Systems to Virtual Information and Knowledge Environments, EJN-Festschrift, Matthias Hemmje Ed., Springer LNCS 3379, November 2004.
• An Architecture for Peer-to-Peer Information Retrieval, in 27th Annual International ACM SIGIR Conference (SIGIR 2004), Workshop on Peer-to-Peer Information Retrieval, July, 2004.
• A Query-Adaptive Partial Distributed Hash Table for Peer-to-Peer Systems", in International Workshop on Peer-to-Peer Computing & DataBases (P2P&DB 2004), Crete, Greece, March 2004.