w3c linked data platform overview
DESCRIPTION
Update on W3C Linked Data Platform http://www.w3.org/TR/ldp as of 10/8/2014TRANSCRIPT
© 2014 IBM Corporation
W3C Linked Data PlatformSteve Speicher, @[email protected]
Linked Data Platform7 October
© 2014 IBM Corporation
Linked Data Platform
2
Agenda
Linked Data
■W3C Linked Data Platform–LDP Resource–LDP Container–LDP Paging
Status
■Related Projects
© 2014 IBM Corporation
Linked Data Platform
Linked Data – Defined by Tim Berners-Lee
1. Use URIs as names for things 2. Use HTTP URIs so that people can look up those names. 3. When someone looks up a URI, provide useful information, using the standards (RDF*,
SPARQL) 4. Include links to other URIs. so that they can discover more things.
He concludes this with: “Simple.”
Reference: “Linked Data”, Tim Berners-Lee, 2006-07-27
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Linked Data Platform
4 October 7, 2014
Linked Data and the Web
Linked Data is a natural extension of the web of documents:
Web of Documents Linked Data
Standard Global Identifier+Locator
Pages are identified by a URL which can also be used to locate the page
Pieces of data are identified by a URL which can also be used to locate the data
Standard Access Protocol
Pages are accessed via HTTP Data is accessed via HTTP
Standard Representation
Pages are served in a standard format: HTML
Data is served in a standard representation: RDF
Standard way of linking related items
Related pages are linked to one another using their URLs
Related pieces of data are linked to one another using their URLs
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Linked Data Platform
Not All Linked Data needs to be Linked Open Data (LOD)
★ Available on the web (whatever format) but with an open licence, to be Open Data
★★ Available as machine-readable structured data (e.g. excel instead of image scan of a table)
★★★ As (2) plus non-proprietary format (e.g. CSV instead of excel)
★★★★ All the above plus, Use open standards from W3C (RDF and SPARQL) to identify things, so that people can point at your stuff
★★★★★ All the above, plus: Link your data to other people’s data to provide context
This does NOT mean all Linked Data must be freely available.
Just like not all web pages are publicly available not all Linked Data needs to be.
Added in 2010 by Tim Berners-Lee: “in order to encourage people, especially government data owners, along the road to good linked data, I have developed this star rating system”
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Linked Data Platform
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Software Configuration Management
Software Configuration Management
Work-item & defect tracking (aka Change Management)
Work-item & defect tracking (aka Change Management)
Build automation & managementBuild automation & management
Test automation & managementTest automation & management
Requirements managementRequirements management
Year 2010 – IBM Rational's Breakthrough
6
Integrate with data & open protocols instead of glue code
“If the entire Web can connect like this, why wouldn't the same idea work for ALM?”
Applying Linked Data to the ALM Integration Challenge: Artifacts such as defects, change requests, and tests become resources exposed as RDF
that can be linked to each other Tools simply access the resources via HTTP following the Linked Data principles
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Challenges of using Linked Data
■ No formal definition
■ State of the art is primarily about publishing read-only data on the web, downloaded and updated as large dumps or via a SPARQL entry point
■ Tim Berners-Lee's four principles are a terrific foundation but don’t go far enough.
■ Developers are left with many unanswered questions:
– How do I create a resource?• It seems obvious that you use POST to create, but what do you POST to?
– Where can I get the list of resources that already exist?– Which vocabulary do I use?– Which media types do I use?– When resources get big, how do I split the information into pages?– How do I specify ordering?
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Linked Data Platform
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Agenda
■Linked Data
W3C Linked Data Platform–LDP Resource–LDP Container–LDP Paging
Status
■Related Projects
© 2014 IBM Corporation
Linked Data Platform
9
Linked Data Platform (LDP)
“A specification for HTTP-based (RESTful) application integration patterns using read/write Linked Data.”
■A set of rules that clarify and extends Tim Berners-Lee's four basic rules focusing on the following concepts:
– LDP Resources (LDPR)– HTTP and RDF techniques to read and write linked data– Resources can be created, modified, deleted and read using standard HTTP methods
(i.e., POST, PUT/PATCH, DELETE, GET).– Cover “RDF sources” as well as “binary resources”
– LDP Containers (LDPC)– An LDPR to which you POST to create new things, GET to find existing things– Similar to what AtomPub does for XML– Available in three flavors: BasicContainer, DirectContainer, and IndirectContainer
– Paging & Ordering– A mechanism to get the content of an LDPR in chunks and specify the order in which
the content is sorted
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Linked Data Platform
Linked Data Platform Resource (LDPR)
Different types:
Some general rules:
1. LDPRs are HTTP resources that can be created, modified, deleted and read using standard HTTP methods (i.e., POST, PUT/PATCH, DELETE, GET).
2. LDPRs use RDF to define their states.
3. You can request a Turtle representation of a LDPR and possibly other reps (e.g., XML/RDF)
4. LDP clients use Optimistic Collision Detection on update (etags).
This is little more than what HTTP already defines.
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Linked Data Platform
http://example.org
LDP Resource – GET a simple example
HTTP/1.1 200 OKETag: "_87e52ce291112"Link: <http://www.w3.org/ns/ldp#Resource>; rel="type"Allow: GET,PUT,PATCH,DELETE,OPTIONS,HEAD
@prefix dcterms: <http://purl.org/dc/terms/>.
@prefix ldp: <http://www.w3.org/ns/ldp#>.
<http://example.org/container1/member1> a o:Cash; dcterms:title “ACME Bank savings account”; o:value 45.00.
GET /container1/member1 HTTP/1.1Host: example.orgAccept: text/turtle
Req
uest
Res
pons
e
container1
member2
member3
member1
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Linked Data Platform
Linked Data Platform Container (LDPC)
Different types:
Some general rules:
1. LDPCs are LDPRs
2. Clients can retrieve the list of resource members of an LDPC using GET
3. New resources are created by POSTing to an LDPC
4. Any resource can be POSTed to an LDPC – not just LDPRs (i.e., LDP-NR and LDPCs)
5. After POSTing a new resource to an LDPC, the new resource will appear as a member until it is deleted.
6. Clients can retrieve information about an LDPC without retrieving a full representation of its content, including its members.
7. On deleting an LDPC the server MAY delete member resources.
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Linked Data Platform
http://example.org
LDP BasicContainer – GET lists existing resources
Link: <http://www.w3.org/ns/ldp#BasicContainer>; rel="type", <http://www.w3.org/ns/ldp#Resource>; rel="type"Removed most HTTP headers to save some space
@prefix dcterms: <http://purl.org/dc/terms/>.
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
@prefix ldp: <http://www.w3.org/ns/ldp#>.
<http://example.org/container1>
a ldp:BasicContainer;
dcterms:title "A very simple container";
ldp:contains
<http://example.org/container1/member1>,
<http://example.org/container1/member2>,
<http://example.org/container1/member3>.
GET /container1 HTTP/1.1Host: example.orgAccept: text/turtle
Req
uest
Res
pons
e
container1
member1
member2
member3
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Linked Data Platform
LDP BasicContainer – POST creates a new resource
HTTP/1.1 201 CREATED
Content-Location: http://example.org/container1/member4
POST /container1 HTTP/1.1Host: example.orgContent-type: text/turtleContent-length: 324
@prefix dcterms: <http://purl.org/dc/terms/>.@prefix o: <http://example.org/ontology/>.
<> a o:Stock; dcterms:title “ACME Co.”; o:value 100.00.
Req
uest
Res
pons
e
http://example.org
container1
member1
member2
member3
+member4
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Linked Data Platform
LDP BasicContainer – GET returns updated list
Removed HTTP headers to save some space
@prefix dcterms: <http://purl.org/dc/terms/>.
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
@prefix ldp: <http://www.w3.org/ns/ldp#>.
<http://example.org/container1>
a ldp:BasicContainer;
dcterms:title "A very simple container";
ldp:contains
<http://example.org/container1/member1>,
<http://example.org/container1/member2>,
<http://example.org/container1/member3>,
<http://example.org/container1/member4>.
GET /container1 HTTP/1.1Host: example.orgAccept: text/turtle
Req
uest
Res
pons
e
http://example.org
container1
member1
member2
member3
member4
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Linked Data Platform
Net worth example
Disclaimer: picture only in UML, does not follow UML constraints
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Linked Data Platform
LDP DirectContainer – Slightly more complex example
<http://example.org/netWorth/nw1> a o:NetWorth; o:asset <http://example.org/netWorth/nw1/assetContainer/a1>, <http://example.org/netWorth/nw1/assetContainer/a2>.
• Members are associated with a resource other than the container
• Membership predicate is domain specific
• Relationship can take two different forms:
• <membershipResource> <ldp:hasMemberRelation> <member>
• <member> <ldp:isMemberOfRelation> <membershipResource>
<http://example.org/netWorth/nw1/assetContainer> a ldp:DirectContainer; dcterms:title "The assets of JohnZSmith"; ldp:membershipResource <http://example.org/netWorth/nw1>; ldp:hasMemberRelation o:asset.
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Linked Data Platform
LDP DirectContainer (continue)
<http://example.org/netWorth/nw1> a o:NetWorth; o:asset <http://example.org/netWorth/nw1/assetContainer/a1>, <http://example.org/netWorth/nw1/assetContainer/a2>, o:liability <http://example.org/netWorth/nw1/liabilityContainer/l1>.
• Several containers can be defined around the same resource (e.g., assets, liabilities)
<http://example.org/netWorth/nw1/assetContainer> a ldp:DirectContainer; dcterms:title "The assets of JohnZSmith"; ldp:membershipResource <http://example.org/netWorth/nw1>; ldp:hasMemberRelation o:asset.
<http://example.org/netWorth/nw1/liabilityContainer> a ldp:DirectContainer; dcterms:title "The liabilities of JohnZSmith"; ldp:membershipResource <http://example.org/netWorth/nw1>; ldp:hasMemberRelation o:liability.
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LDP IndirectContainer – More complex example
<http://example.org/netWorth/nw1> a o:NetWorth; o:advisor <advisorContainer/bob#me>, <advisorContainer/marsha#me>.
• Supports listing non-information resource as members
<http://example.org/advisors/> a ldp:IndirectContainer; dcterms:title "The asset advisors of JohnZSmith"; ldp:membershipResource <http://example.org/netWorth/nw1>; ldp:hasMemberRelation o:advisor; ldp:insertedContentRelation foaf:primaryTopic; ldp:contains <advisorContainer/bob>, <advisorContainer/marsha>.
<http://example.org/advisorContainer/bob> foaf:primaryTopic <#me>.
<#me> a foaf:Person; foaf:name "Bob Marlow".
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Linked Data Platform
LDP Non-RDF Sources a.k.a “Binary Resources”
HTTP/1.1 201 CREATED
Content-Location: http://example.org/attachments/myimage
Link: <http://example.org/mycontainer/myimage-info>; rel=describedby
POST /attachments/ HTTP/1.1Host: example.orgContent-type: image/pngContent-length: 1048Slug: myimage
[binary content not displayed]
Req
uest
Res
pons
e
Created by POSTing to a Container
As a result the server may create two resources:– An LDP Non-RDF Source that is added as a member– An LDP RDF Source that describes the LDP-NR
http://example.org
attachments
member1
member2
member3
+myimage
+myimage-info
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Linked Data Platform
LDP Paging
HTTP/1.1 303 See Other
Location: <http://example.org/customer-relations?page1>
GET /customer-relations HTTP/1.1Host: example.orgAccept: text/turtlePrefer: return=representation; max-triple-count="500"R
eque
stR
espo
nse
Client can request to only be sent a certain amount of data (# of triples, records, or kbytes)
As a result the server may redirect to a first page
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Linked Data Platform
LDP Paging – Getting the first page
HTTP/1.1 200 OKRemoved some HTTP headers to save some space
Link: <http://www.w3.org/ns/ldp#Resource>; rel="type", <http://www.w3.org/ns/ldp#Page>; rel="type"Link: <http://example.org/customer-relations?p=2>; rel='next'Link: <http://example.org/customer-relations>; rel='canonical'; etag="customer-relations-v1”
Removed other prefix declarations
<> a o:CustomerRelations; dcterms:title "The customer information for Example Co."; o:client <#JohnZSmith>, <#BettyASmith>, <#JoanRSmith>.
<#JohnZSmith> a foaf:Person; o:status o:ActiveCustomer;
GET /customer-relations?page1 HTTP/1.1Host: example.orgAccept: text/turtlePrefer: return=representation; max-triple-count="500"R
eque
stR
espo
nse
Link Headers indicate: this is a page and provides link to the next page
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Linked Data Platform
LDP Paging – Detecting changes
HTTP/1.1 200 OKRemoved some HTTP headers to save some space
Link: <http://www.w3.org/ns/ldp#Resource>; rel="type", <http://www.w3.org/ns/ldp#Page>; rel="type"Link: <http://example.org/customer-relations?p=2>; rel='next'Link: <http://example.org/customer-relations>; rel='canonical'; etag="customer-relations-v1”
Removed other prefix declarations
<> a o:CustomerRelations; dcterms:title "The customer information for Example Co."; o:client <#JohnZSmith>, <#BettyASmith>, <#JoanRSmith>.
<#JohnZSmith> a foaf:Person; o:status o:ActiveCustomer;
GET /customer-relations?page1 HTTP/1.1Host: example.orgAccept: text/turtlePrefer: return=representation; max-triple-count="500"R
eque
st
Link Header provides link to the resource being paged with etag to detect changes
Res
pons
e
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Linked Data Platform
LDP Paging – Optimizing workflow with HTTP 2NN
HTTP/1.1 2NN Contents of RelatedRemoved some HTTP headers to save some space
Location: <http://example.org/customer-relations?page1>Link: <http://www.w3.org/ns/ldp#Resource>; rel="type", <http://www.w3.org/ns/ldp#Page>; rel="type"Link: <http://example.org/customer-relations?p=2>; rel='next'Link: <http://example.org/customer-relations>; rel='canonical'; etag="customer-relations-v1”
Removed other prefix declarations
<> a o:CustomerRelations; dcterms:title "The customer information for Example Co."; o:client <#JohnZSmith>, <#BettyASmith>, <#JoanRSmith>.
<#JohnZSmith> a foaf:Person;
GET /customer-relations HTTP/1.1Host: example.orgAccept: text/turtlePrefer: return=representation; max-triple-count="500"Prefer: contents-of-related
Req
uest
When client supports 2NN, server can directly send first page back
Res
pons
e
© 2014 IBM Corporation
Linked Data Platform
LDP Paging – Ordering of LDP Containers
Removed some HTTP headers to save some space
Link: ... <http://www.w3.org/ns/ldp#Page>; rel="type"Link: <http://example.org/netWorth/nw1/assetContainer/sortedSequence/>; rel='http://www.w3.org/ns/ldp#pageSequence’
Removed other prefix declarations
<> a ldp:DirectContainer; ldp:membershipResource <http://example.org/netWorth/nw1>; ldp:hasMemberRelation o:asset; ldp:insertedContentRelation ldp:MemberSubject; ldp:contains <a1>, <a2>, <a3>.
<http://example.org/netWorth/nw1> a o:NetWorth; o:asset <a1>, <a3>, <a2>.
<a1> a o:Stock; o:marketValue 100.00 .
@base <http://example.org/netWorth/nw1/assetContainer/sortedSequence/> .<> ldp:pageSortCriteria ( <#Sort-o.marketValue-Ascending> ).
<#Sort-o.marketValue-Ascending> a ldp:pageSortCriterion; ldp:pageSortOrder ldp:Ascending; ldp:pageSortPredicate o:marketValue.
Order used for paging is specified via a resource providing a list of sort criteria
Res
pons
e
© 2014 IBM Corporation
Linked Data Platform
26
Agenda
■Linked Data
W3C Linked Data Platform–LDP Resource–LDP Container–LDP Paging
Status
■Related Projects
© 2014 IBM Corporation
Linked Data Platform
27
Status
Published Candidate Recommendation of LDP on 19 June 2014– Proposed Recommendation expected by the end of September– Test suite available for implementers
About to publish Second Last Call of LDP Paging– Provide for negotiation client-server– Provide for more certainty– Review period to end around the end of September 2014
Updated Use Cases & Requirements WG Note on 13 March 2014
Published Primer WG Note on 26 June 2014
About to publish Best Practices & Guidelines WG Note
About to publish Access Control Use cases & requirements WG Note
About to publish First Public Working Draft of LD PATCH! Seeking feedback on direction!
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Linked Data Platform
Looking Forward
Several necessary and desirable features are not in scope for LDP 1.0:
■Security – Authentication, Access control– WG is chartered to identify requirements and use cases– Several technologies can already be used: OAuth, WebId, etc.
Validation/Constraints– RDFS and OWL are for inference not validation– There is currently no standard technology to perform validation
• RDF Data Shapes Working Group has launched!
Deployment challenges– URL changes– Server cloning– Cross-server query
LDP.Next Wish List: https://www.w3.org/2012/ldp/wiki/LDPNext
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Linked Data Platform
29
Agenda
■Linked Data
■W3C Linked Data Platform–LDP Resource–LDP Container–LDP Paging
■Status
Related Projects
© 2014 IBM Corporation
Linked Data Platform
LDP Implementations
SDK and supporting tools to help the community to adopt OSLC specifications and build compliant tools
Implementation of LDP that can be extended and deployed easily by organizations who want to publish data or build custom applications
Marmotta
For a more complete list see: http://www.w3.org/wiki/LDP_Implementations
Several implementations are already available:
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Linked Data Platform
Automation
Monitoring
Community driven and governed 400+ registered community members Workgroup members from 34+ organizations
Wide range of interests, expertise, & participation Open specifications for numerous disciplines Defined by scenarios – solution oriented Implementations from IBM, BPs, and Others
Based on Linked Data
Open Services for Lifecycle CollaborationLifecycle integration inspired by the web
Inspired by the web
ProvenFree to use and share
OpenChanging the industry
Innovative
Open Services for Lifecycle Collaboration (OSLC)Working to improve the way software lifecycle tools share data
open-services.net
For more info see: http://open-services.net