resourcesync was funded by the sloan foundation & jisc a modular framework for web-based...
TRANSCRIPT
ResourceSync was funded by the Sloan Foundation & JISC
A Modular Framework for Web-Based Resource Synchronization
Martin KleinLos Alamos National Laboratory
@mart1nkle1n
http://www.openarchives.org/rs #resourcesync
Herbert Van de SompelLos Alamos National Laboratory
@hvdsomp
ResourceSync
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
ResourceSync
• Collaboration between NISO and the Open Archives Initiative
• Funded by the Sloan Foundation and JISC
• Goal: Devise a specification for web-based resource synchronization
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
This ResourceSync Presentation
• Problem Domain
• Scope
• Framework - Overview
• Framework – Technology
• Demonstration
• Status
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Background - OAI-PMH
• Recurrent metadata exchange from a Data Provider to Service Providers
• XML metadata only
• Repository centric
• Devised 1999-2002, prior to REST, prior to dominance of web search engines
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Revisit the Problem Domain - ResourceSync
• Synchronization of resources from a Source to Destinations
• Web resources, anything with an HTTP URI & representation
• Resource centric
• Devised 2012-2013, leverages key ingredients of web interoperability, existing specifications, existing Search Engine Optimization practice
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Problem Statement
• Consideration:• Source (server) A has resources that change over time: they
get created, modified, deleted• Destination (servers) X, Y, and Z leverage (some)
resources of Source A
• Problem:• Destinations want to keep in step with the resource changes
at Source A
A Source’s Resources
A Source’s Resources Evolve over Time
A Source’s Resources Evolve over Time
A Source’s Resources Evolve over Time
A Source’s Resources Evolve over Time
A Source’s Resources Evolve over Time
A Source’s Resources Evolve over Time
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Problem Statement
• Consideration:• Source (server) A has resources that change over time: they
get created, modified, deleted• Destination (servers) X, Y, and Z leverage (some)
resources of Source A
• Problem:• Destinations want to keep in step with the resource changes
at Source A
• Goal:• Design an approach for resource synchronization aligned
with the Web Architecture that has a fair chance of adoption by different communities
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
This ResourceSync Presentation
• Problem Domain
• Scope
• Framework - Overview
• Framework – Technology
• Demonstration
• Status
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Scope – Collection Size
• Size of a Source’s resource collection:
• A few resources - small web sites, repositories
• Millions of resources – large repositories, datasets, linked data collections
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Scope – Change Frequency
• Change frequency of a Source’s resources:
• Low – daily, weekly, monthly
• High – seconds, minutes
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Scope – Synchronization Latency
• Destination’s requirements regarding synchronization latency:
• High latency acceptable
• Low latency essential
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Scope – Collection Coverage
• Destination’s requirements regarding the coverage of a Source’s resources:
• Partial coverage of the Source’s resources acceptable
• Full coverage of the Source’s resources verifiable
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Scope – Bitstream Accuracy
• Destination’s requirements regarding bitstream accuracy:
• Unverifiable bitstream accuracy acceptable
• Verifiable bitstream coverage essential
One to One Synchronization
One to Many – Master Copy
Many to One - Aggregator
Selective Synchronization
Metadata Harvesting
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
This ResourceSync Presentation
• Problem Domain
• Scope
• Framework - Overview
• Framework – Technology
• Demonstration
• Status
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
A Source’s Resources Evolve over Time
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Solution Perspective - Destination
• Destination needs regarding synchronization:
• Baseline synchronization: Initial catch-up operation to align with the Source’s resources
• Incremental synchronization: Remain synchronized as the Source’s resources evolve
• Audit: Destination determines whether it effectively is in sync with the Source- Bitstream accuracy- Coverage of resources
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Solution Perspective - Source
• Source communicates about the state of its resources:
• Publish inventory: snapshot of the state of resources at a moment in time
• Publish changes: enumeration of resource changes that occurred during a temporal interval
• Notify about changes: send notifications as changes occur
• Communication payload:• Minimal, e.g. HTTP URI of resource• Additional, e.g. content-based hash of resource
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Resource List
• In order to meet a Destination’s need for baseline synchronization, the Source may publish a Resource List
• A Resource List is an inventory, a snapshot of existing resources
• Per resource, it minimally provides the resource’s URI
• Process:- Destination obtains the Resource List- Destination obtains listed resources by their URI- Optimization: Resource Dump, a list pointing to ZIP files
that contain resource representations
Publish Resource List: Inventory at Tx
Resource List @Tx = { A ; B ; C }
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Change List
• In order to meet a Destination’s need for incremental synchronization, the Source may publish a Change List
• A Change List enumerates resource change events that occurred in a temporal interval
• For each event, it minimally lists datetime, URI of the resource, the nature of the change
• Process:- Destination obtains the Change List- Destination obtains created/updated resources, removes
deleted resources- Optimization: Change Dump
Publish Change List: Resource Changes During Interval Ty-Tz
Change List [Ty,Tz] = { A updated @Tc ; B updated @Tc ; C created @Td ; D deleted @Te ; C updated @Tf }
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Change Notification
• In order to meet a Destination’s need for incremental synchronization and low latency, the Source may send Change Notifications
• A Change Notification conveys resource change events as they occur
• For each event, it minimally lists datetime, URI of the resource, the nature of the change
- Process:- Destination receives Change Notification- Destination obtains created/updated resources, removes
deleted resources
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Send Change Notification – Resource Changes at Ta
Change Notification @Ta = { A updated @Ta }
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Send Change Notification – Resource Changes at Tb
Change Notification @Tb = { D updated @Tb }
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Send Change Notification – Resource Changes at Tc
Change Notification @Tc = { A updated @Tc ; B updated @Tc }
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Send Change Notification – Resource Changes at Td
Change Notification @Td = { C created @Td }
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Send Change Notification – Resource Changes at Te
Change Notification @Te = { D deleted @Te }
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Send Change Notification – Resource Changes at Tf
Change Notification @Tf = { C updated @Tf }
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Communication Payload – Metadata & Links
• A Source may provide additional metadata and links pertaining to resources conveyed in Resource Lists, Change Lists, Change Notifications
• Metadata about a resource: content encoding, content length, mime type, content-based hash
• Linking to related resources: mirror copies, alternate representations, resource versions, diff between current and previous version, metadata-to-content link, content-to-metadata link, collection membership, etc.
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Communication Payload – Metadata – Hash
• In order to meet a Destination’s need for audit, the Source may provide a content-based hash pertaining to a resource
• Source computes the content-based hash for a resource
• Source provides the hash as metadata pertaining to the resource in its communication payload
• Destination processes communication payload, obtains the resource
• Destination computes the content-based hash for the obtained resource, compares with the Source’s
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Communication Payload – Link – Interlink Metadata & Content
• In order to allow a Destination to establish the relationship between a Source’s metadata and a Source’s content, the Source may provide appropriate links
• Metadata resources and content resources are just resources identified by HTTP URIs
• Both can independently be subject to synchronization and can be interlinked using appropriately typed links
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Communication Payload – Link – Link to Diff
• In order to minimize content transfer, a Source may link to a diff between the previous and the new version of a resource
• Destination can obtain the diff and patch its (previous) version of the resource
• Connection between the resource and the diff is established by means of appropriately typed link
• Nature of the diff is established by means of MIME type- Few diff MIME types exist. Communities can establish
their own.
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Further Framework Characteristics
• Modular: A Source does not have to implement all capabilities
• Source decides which capabilities to support based on local and community requirements
• Sets of Resources: Division of a Source’s resource collection in logical groupings.
• Supported capabilities can differ per set
• Discovery: Mechanisms for Destinations to determine whether and how a Source supports ResourceSync
• Based on conventions for web discovery and documents that detail the level of support
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
This ResourceSync Presentation
• Problem Domain
• Scope
• Framework - Overview
• Framework – Technology
• Demonstration
• Status
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Sitemap Protocol
• ResourceSync builds on the Sitemap protocol used by major search engines
• Similarity between resource synchronization and resource discovery/indexing
• Extends the Sitemap protocol to meet synchronization needs• Cf. Metadata and Links
• Sitemap document format is used throughout the framework to express Resource Lists, Change Lists, etc.• Type of ResourceSync document can be determined
through explicit declaration
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Common Sitemap
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9”>
<url> <loc>http://example.com/res1</loc> <lastmod>2013-01-02T13:00:00Z</lastmod> </url>
<url> <loc>http://example.com/res2</loc> <lastmod>2013-01-02T14:00:00Z</lastmod> </url> …</urlset>
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Resource List
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:rs="http://www.openarchives.org/rs/terms/"> <rs:md capability="resourcelist" at="2013-01-03T09:00:00Z” /> <url> <loc>http://example.com/res1</loc> <lastmod>2013-01-02T13:00:00Z</lastmod> <rs:md hash="md5:1584abdf8ebdc9802ac0c6a7402c03b6" length="8876" type=”application/pdf” /> </url> <url> … </url></urlset>
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Change List
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:rs="http://www.openarchives.org/rs/terms/"> <rs:md capability=”changelist" from="2013-01-02T09:00:00Z” until="2013-01-03T09:00:00Z” /> <url> <loc>http://example.com/res2</loc> <lastmod>2013-01-02T13:00:00Z</lastmod> <rs:md change=”updated” /> <rs:ln href=“http://example.com/res2/meta” rel=“describedby” /> </url> <url> … </url></urlset>
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Change Notification
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:rs="http://www.openarchives.org/rs/terms/"><url> <loc>http://example.com/res3</loc> <lastmod>2013-01-02T13:00:00Z</lastmod> <rs:md change=”updated” type=”application/json” /> <rs:ln href=“http://example.com/res3/diff” rel=“http://www.openarchives.org/rs/terms/patch” type=“application/json-patch”/> </url> <url> … </url></urlset>
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
PubSubHubbub Protocol
• ResourceSync builds on the PuSH protocol used for syndication of Atom/RSS feeds
• Introduces a novel use for pushing change notifications from a Source to subscribing Destinations
• Destinations subscribe to a Source’s change notifications via a Hub
• The Source pushes change notifications out to the Hub
• The Hub relays change notifications from the Source to the subscribing Destinations
Destination Discovers Source’s Notification Channel & Hub
Destination Subscribes to Source’s Notification Channel
Source Sends Change Notification to Hub
Hub Relays Change Notification to Destination(s)
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
This ResourceSync Presentation
• Problem Domain
• Scope
• Example Use Cases
• Framework Characteristics
• Demonstration
• Status
Source Sends Change Notifications
Destination Acts Upon Change Notifications
Observe the State of Source and Destination
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
This ResourceSync Presentation
• Problem Domain
• Scope
• Example Use Cases
• Framework Characteristics
• Demonstration
• Status
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Status of Specifications
• ResourceSync Core Specification currently in NISO Voting Pool• Ends April 16 2014• Please vote if you are a NISO member• If vote is positive should be ANISO/NISO Z39.99 by July 2014• Spec on OAI web site fully aligned with NISO Standard
• ResourceSync Notification Specification currently in beta• Ongoing tests with PubSubHubbub• Hub, Source, Destination Python software to be released • Public Hub for testing will be made available
• ResourceSync Archive Specification currently in beta
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Pointers
• Specification
http://www.openarchives.org/rs/http://www.openarchives.org/rs/resourcesynchttp://www.openarchives.org/rs/notificationhttp://www.openarchives.org/rs/archives
• List for public comment
https://groups.google.com/d/forum/resourcesync
• Building blocks
http://sitemaps.orghttps://code.google.com/p/pubsubhubbub/
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Papers
• Klein, M., and Van de Sompel, H. (2013) Extending Sitemaps for Resourcesync. http://arxiv.org/abs/1305.4890 ACM/IEEE JCDL 2013
• Haslhofer, B., Warner, S, Lagoze, C., Klein, M., Sanderson, R., Nelson, M.L. and Van de Sompel, H. (2013) ResourceSync: Leveraging Sitemaps for Resource Synchronization. http://arxiv.org/abs/1305.1476 WWW 2013 Developer Track
• Klein, M., Sanderson, R., Van de Sompel, H., Warner, S, Haslhofer, B., Lagoze, C., and Nelson, M.L. (2013) A Technical Framework for Resource Synchronization. http://dx.doi.org/10.1045/january2013-klein D-Lib Magazine.
• Van de Sompel, H., Sanderson, R., Klein, M., Nelson, M.L., Haslhofer, B., Warner, S, and Lagoze, C. (2012) A Perspective on Resource Synchronization. http://dx.doi.org/10.1045/september2012-vandesompel D-Lib Magazine.
Herbert Van de Sompel, Martin Klein - ResourceSyncCNI Spring 2014, St. Louis, MO, March 31 2014
Acknowledgments
• Editors: Martin Klein, Robert Sanderson, Herbert Van de Sompel (Los Alamos National Laboratory), Simeon Warner (Cornell University), Graham Klyne ( University of Oxford), Bernhard Haslhofer (University of Vienna), Michael L. Nelson (Old Dominion University), Carl Lagoze ( University of Michigan)
• Contributors: Peter Murray (Lyrasis), Todd Carpenter, Nettie Lagace (NISO), Richard Jones (Cottage Labs), Stuart Lewis (University of Edinburgh), Paul Walk (University of Edinburgh), Jeff Young (OCLC), Shlomo Sanders (Ex Libris), Kevin Ford (Library of Congress)
• Demonstration: Martin Klein, Harihar Shankar, Herbert Van de Sompel (Los Alamos National Laboratory)
ResourceSync was funded by the Sloan Foundation & JISC
A Modular Framework for Web-Based Resource Synchronization
Martin KleinLos Alamos National Laboratory
@mart1nkle1n
http://www.openarchives.org/rs #resourcesync
Herbert Van de SompelLos Alamos National Laboratory
@hvdsomp
ResourceSync