overview of w3c linked data platform 20140410

© 2014 IBM Corporation

W3C Linked Data PlatformArnaud J Le Hors, IBM Linked Data Standards [email protected]

Linked Data Platform10 April 2014

© 2014 IBM Corporation2

Linked Data Platform

Agenda

➢ Linked Data

■ Using Linked Data for Application Integration

■ Challenges of using Linked Data for Application Integration

■ W3C Linked Data Platform

■ Related Projects



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

http://www.w3.org/DesignIssues/LinkedData.html




© 2014 IBM Corporation4 April 10, 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



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”



Agenda

■ Linked Data

➢ Using Linked Data for Application Integration






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

IBM Rational's use of Linked Data for Application Integration

7

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



Applying Linked Data to ALM – A development tools example

TestCase 14 is blocked by Issue 973http://srv/qm/tc/14 qm:blockedBy http://apache.org/jira/HTTPCLIENT-973





Issue 973 depends on Bug 318 http://apache.org/jira/HTTPCLIENT-973 cm:dependsOn http://bugs.sun.com/? id=7172318

Issue 973 is owned by Joe http://apache.org/jira/HTTPCLIENT-973 dc:contributor http://joecoder.me





Issue 973 depends on Bug 318 http://apache.org/jira/HTTPCLIENT-973 cm:dependsOn http://bugs.sun.com/? id=7172318

Issue 973 is owned by Joe http://apache.org/jira/HTTPCLIENT-973 dc:contributor http://joecoder.me

Joe is a committer for Apachehttp://joecoder.me doap:committer http://apache.org



Agenda

■ Linked Data


➢ Challenges of using Linked Data for Application Integration





Challenges of using Linked Data for Application Integration

■ 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?



Agenda

■ Linked Data



➢ W3C Linked Data Platform




W3C Linked Data Platform (LDP) Working Group

Workgroup membership spans 50 participants from 30 organizations

Chair: Arnaud J Le Hors (IBM)

Working towards defining a clear definition of “Linked Data”, in the form of a W3C Recommendation

– Based on Tim Berners-Lee four principles of Linked Data

Chartered to produce a “Linked Data Platform” specification that:– HTTP-based (RESTful) application integration patterns using read/write Linked Data– Will complement SPARQL and will be compatible with standards for publishing Linked Data,

bringing the data integration features of RDF to RESTful, data-oriented software development.

Chartered to deliver a W3C Recommendation in 1H2014

Details @ http://www.w3.org/2012/ldp



Linked Data Platform (LDP)

■ A set of rules that clarify and extends Tim Berners-Lee's four basic rules focusing on the following two concepts:

– LDP Resources (LDPR)– HTTP and RDF techniques to use to read and write linked data

– 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



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.



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.



http://example.org

LDP BasicContainer – GET lists existing resources

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/member3>.

GET /container1 HTTP/1.1Host: example.orgAccept: text/turtle

Req

uest

Res

pons

e

container1

member1

member2

member3



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.R

eque

stR

espo

nse

http://example.org

container1

member1

member2

member3

+member4



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/member4>.

GET /container1 HTTP/1.1Host: example.orgAccept: text/turtle

Req

uest

Res

pons

e

http://example.org

container1

member1

member2

member3

member4



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.



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.



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".



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



LDP Status update

Published First Last Call Working Draft on 30 July 2013

Received several comments that required changes:– Did not provide enough interoperability, especially for “vanilla clients”

• Too many SHOULDs, not enough MUSTs• Silent failure is a big NO NO: e.g., servers may discard triples sent by client

– Paging mechanism to be moved to HTTP layer

Published Second Last Call Working Draft on 11 March 2014– A lot more MUSTs– Three types of containers– Differentiates containment from membership– Moved paging and ordering out– Replaced non-member properties with use of Prefer header– Added support for interaction models

Review period ended on April 2 with a few minor comments

Candidate Recommendation expected by the end of the April

Proposed Recommendation in June



LDP Status update (continue)

Other deliverables in the works:

– Use Cases & Requirements (WG Note – updated on 13 March 2014)– Paging & Ordering (Working Draft)– Primer (WG Note)– Best Practices & Guidelines (WG Note)– Access Control Use cases & requirements (WG Note)



Looking Forward

Linked Data has the potential of becoming an important application integration model in the enterprise but 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

• Discussions to launch a new effort at W3C are underway.

Deployment challenges– URL changes– Server cloning– Cross-server query



Agenda

■ Linked Data




➢ Related Projects



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:



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

http://open-services.net/members

http://open-services.net/participate

overview of w3c linked data platform 20140410

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