WWW2013 Linked Data Platform (LDP) 20130515

© 2013 IBM Corporation
Linked Data Platform
Arnaud J Le Hors, IBM Linked Data Standards Lead
lehors@us.ibm.com
15 May 2013

© 2013 IBM Corporation2
Agenda
➢ IBM Rational's ALM Integration Challenge
■ Linked Data
■ Applying Linked Data to ALM
■ Challenges of using Linked Data
■ W3C Linked Data Platform
■ Related Projects

Software Development Tools : Year 2000 - point products
User complaints
–Need tools to work better
–Need tools to work together
Software
Configuration
Management
Work-item & defect
tracking (aka Change
Management)
Build automation
& management
Test automation
& management
Requirements
management

ALM Solution
• Developer complaints
– Clumsy integrations
– Want best-of-breed choice
• Management complaints
– Need governance, metrics,
reports, …
• Mixed Tool Environments
– Open-source offerings with DIY
integration
– 3rd
party ALM suites
Software
Configuration
Management
Work-item & defect
Management)
Build automation
& management
Test automation
& management
Requirements
management
4
Year 2005 – Application Lifecycle Management (ALM) V1

Agenda
■ IBM Rational's ALM Integration Challenge
➢ Linked Data

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

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”

W3C Linked Data Specifications
Domain Specifications
Protocol  HTTP
Data Model  RDF
Serialization Format  RDF/XML
 Turtle
 TriG
 RDFa
 JSON-LD
Query  SPARQL
 There are other specifications that relate to the Semantic Web such as OWL that you can
use in addition but you don't need to use any of the Semantic Web features (ontologies,
inferencing, reasoning, etc) to make use of Linked Data.

Agenda
■ Linked Data
➢ Applying Linked Data to ALM

Software
Configuration
Management
Work-item & defect
Management)
Build automation
& management
Test automation
& management
Requirements
management
Year 2010 – IBM Rational's Breakthrough
10
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 973
http://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 Apache
http://joecoder.me doap:committer http://apache.org

Agenda
■ Linked Data
➢ Challenges of using Linked Data

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 containers 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.
 Published Linked Data Platform Latest Public Working Draft on 7 March 2012
 Published Use Case & Requirements First Public Working Draft on 31 January 2013
 On track to deliver a W3C Candidate Recommendation in 2013
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 concepts:
– LDP Resources (LDPR)
– HTTP and RDF techniques to use to read and write linked data
– LDP Containers (LDPC)
– A LDPR to which you POST to create new things, GET to find existing things
– Similar to what AtomPub does for XML
– Paging
– A mechanism to get the content of a LDPC in chunks
– Ordering
– A mechanism to specify the order in which the content of a LDPC is sorted

Linked Data Platform Resource (LDPR)
Some 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.
5. LDPRs set rdf:type explicitly.
6. LDP clients expect to encounter unknown properties and content.
7. LDP clients do not assume the type of a resource at the end of a link.

http://example.org
LDP Resource – GET a simple example
Removed HTTP headers to save some space
@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/1.1
Host: example.org
Accept: text/turtle
RequestResponse
container1
member1
member2
member3

Linked Data Platform Container (LDPC)
Some rules:
1. LDPCs are LDPRs
2. Clients can retrieve the list of resource members of an LDPC using GET
3. New resources are created using POST
4. Any resource can be POSTed to an LDPC – not just LDPRs
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 Container – GET a simple example
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
<http://example.org/container1>
a ldp:Container;
dcterms:title "A very simple container";
rdfs:member
<http://example.org/container1/member1>,
<http://example.org/container1/member3>.
GET /container1 HTTP/1.1
Host: example.org
Accept: text/turtle
RequestResponse
container1
member1
member2
member3

LDP Container – Create resource and add
HTTP/1.1 201 CREATED
Content-Location: http://example.org/container1/member4
POST /container1 HTTP/1.1
Host: example.org
Content-type: text/turtle
Content-length: 324
@prefix o: <http://example.org/ontology/>.
<>
a o:Stock;
dcterms:title “ACME Co.”;
o:value 100.00.
RequestResponse
http://example.org
container1
member1
member2
member3
+member4

LDP Container – Get updated
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
<http://example.org/container1>
a ldp:Container;
dcterms:title "A very simple container";
rdfs:member
<http://example.org/container1/member4>.
GET /container1 HTTP/1.1
Host: example.org
Accept: text/turtle
RequestResponse
http://example.org
container1
member1
member2
member3
member4

LDP Container – Slightly more complex example
# The following is the representation of
# http://example.org/netWorth/nw1
@prefix o: <http://example.org/ontology/>.

<http://example.org/netWorth/nw1>
a o:NetWorth;
o:asset
<http://example.org/netWorth/nw1/assetContainer/a1>,
<http://example.org/netWorth/nw1/assetContainer/a2>.

<http://example.org/netWorth/nw1/assetContainer>
a ldp:Container;
dcterms:title "The assets of JohnZSmith";
ldp:membershipSubject <http://example.org/netWorth/nw1>;
ldp:membershipPredicate o:asset.
• Membership predicate is something other than rdfs:member (o:asset)
• Subject for members is something other than the container

LDP Container – Inlined members
# chopped @prefix
a o:NetWorth;
o:asset
a ldp:Container;
<http://example.org/netWorth/nw1/assetContainer/a1>
a o:Stock;
o:value 10000.
a o:Bond;
o:value 20000.
• Statements about the member resources included with container representation response
• Note: how much is included is up to the server and application domain specific

LDP Container – Paging (first page)
# Request-URI: http://example.org/netWorth/nw1?firstPage
# omitted @prefix
a o:NetWorth;
o:asset
a ldp:Container;
bp:membershipSubject <http://example.org/netWorth/nw1>;
bp:membershipPredicate o:asset.
<http://example.org/netWorth/nw1/assetContainer?firstPage>
a ldp:Page;
ldp:pageOf <http://example.org/netWorth/nw1/assetContainer>;
ldp:nextPage <http://example.org/netWorth/nw1/assetContainer?p=2>.
a o:Stock;
o:value 100.00.
a o:Cash;
o:value 50.00.
• New ldp:Page resource
• Members of containers are paged, not HTTP responses

LDP Container – Paging (last page)
# Request-URI: http://example.org/netWorth/nw1/assetContainer?p=2
# omitted @prefix
a o:NetWorth;
o:asset
a bp:Container;
bp:membershipSubject <http://example.org/netWorth/nw1>;
bp:membershipPredicate o:asset.
<http://example.org/netWorth/nw1/assetContainer?p=2>
a ldp:Page;
ldp:nextPage rdf:nil.
a o:Stock;
dcterms:title "Big Co.";
o:value 200.02.
• Last page indicated by rdf:nil

LDP Container – Paging (ordering)
# Request-URI: http://example.org/netWorth/nw1/assetContainer?firstPage
# omitted @prefix
a o:NetWorth;
o:asset
a ldp:Container;
<http://example.org/netWorth/nw1/assetContainer?firstPage>
a ldp:Page;
ldp:containerSortPredicates (o:value).
a o:Stock;
o:value 100.00.
a o:Cash;
o:value 50.00.
• Order indicated by ldp:containerSortPredicates
• No ordinal predicate introduced, leverage domain model

LDP Working Group Activity
 Changes aim at making the specification:
– More broadly applicable
• Moved several restrictions to “Deployment Guide” - a set of best practices
(e.g., datatypes, common properties)
• Turtle is the default serialization format
– More precise
• Removed uncertainty (e.g., “MAY” → “MUST”)
• Changed to be more explicit and less implicit
 Samples of issues being discussed:
– Container
• Do member resources get deleted when a Container is deleted?
• How do I create a Container?
• Can Containers be nested?
• How do I find the first Container?
– Paging of Resources, not just Containers?
– Binary resources - How do I add a non-RDF resource to a Container?
– PATCH - What format to use?

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
 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 organisations 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 Collaboration
Lifecycle integration inspired by the web
Inspired by the web
Proven
Free to use and share
Open
Changing the industry
Innovative
Open Services for Lifecycle Collaboration (OSLC)
Working to improve the way software lifecycle tools share data
open-services.net
NEWS: Technical Work moving to OASIS - Look for a new OASIS Member Section!

• Based on parts of
OSLC Core
• Foundation for future
OSLC Core
Specifications
OSLC’s Big Picture
Open Services for Lifecycle Collaboration
Lifecycle integration inspired by the web
LINKED DATA PLATFORM WORKING GROUP
Future Home of
OSLC Spec Dev
The Resource
for OSLC
Implementers
Inspired by the web
Proven
Free to use and share
Open
Changing the industry
InnovativeOSLC:
Tests, Libraries, Samples, Examples,
Reference Implementations
Scenario-driven &
Solution-oriented
Generally applicable: specs available for many
domains covering ALM, DevOps, ISM, and
PLM
Leading choice for
strategic integration
technology
36

WWW2013 Linked Data Platform (LDP) 20130515

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WWW2013 Linked Data Platform (LDP) 20130515