LDP

RESTful Linked Data. W3C standard for managing RDF resources via HTTP.

Overview

The Linked Data Platform (LDP) is a W3C Recommendation that defines how to read and write Linked Data using standard HTTP operations. It's the foundation that Solid builds upon.

Key Concepts

Resources and Containers

┌─────────────────────────────────────────────────────────────────┐
│                     LDP Concepts                                │
├─────────────────────────────────────────────────────────────────┤
│                                                                 │
│   LDP Resource (LDP-RS)                                        │
│   └── Any resource with RDF content                            │
│       └── GET returns RDF (Turtle, JSON-LD, etc.)              │
│                                                                 │
│   LDP Non-RDF Resource (LDP-NR)                                │
│   └── Binary or non-RDF content                                │
│       └── GET returns the actual bytes                         │
│       └── Has associated RDF description                        │
│                                                                 │
│   LDP Container (LDP-C)                                        │
│   └── Collection of resources (like a folder)                  │
│       └── POST creates new children                            │
│       └── Contains membership triples                          │
│                                                                 │
└─────────────────────────────────────────────────────────────────┘

Container Types

Type	Description
Basic Container	Simple containment
Direct Container	Custom membership predicates
Indirect Container	Membership via derived URIs

HTTP Operations

CRUD Mapping

Operation	HTTP Method	Description
Create (in container)	POST	Add new resource to container
Create (at URL)	PUT	Create resource at specific URL
Read	GET	Retrieve resource
Update (replace)	PUT	Replace entire resource
Update (partial)	PATCH	Modify parts of resource
Delete	DELETE	Remove resource

Examples

Read a Resource

GET /alice/profile HTTP/1.1
Host: pod.example
Accept: text/turtle

HTTP/1.1 200 OK
Content-Type: text/turtle

@prefix foaf: <http://xmlns.com/foaf/0.1/> .

<#me> a foaf:Person ;
    foaf:name "Alice" .

Create in Container

POST /alice/posts/ HTTP/1.1
Host: pod.example
Content-Type: text/turtle
Slug: my-first-post

@prefix schema: <https://schema.org/> .

<> a schema:BlogPosting ;
    schema:headline "Hello World" ;
    schema:text "My first post!" .

HTTP/1.1 201 Created
Location: /alice/posts/my-first-post

Update with PATCH

PATCH /alice/profile HTTP/1.1
Host: pod.example
Content-Type: text/n3

@prefix solid: <http://www.w3.org/ns/solid/terms#> .

DELETE { <#me> foaf:name "Alice" }
INSERT { <#me> foaf:name "Alice Smith" }
WHERE { <#me> foaf:name "Alice" }

Content Negotiation

LDP supports multiple RDF formats:

Format	Media Type
Turtle	text/turtle
JSON-LD	application/ld+json
N-Triples	application/n-triples
RDF/XML	application/rdf+xml

Request your preferred format:

GET /resource HTTP/1.1
Accept: application/ld+json

Link Headers

LDP uses Link headers extensively:

HTTP/1.1 200 OK
Link: <http://www.w3.org/ns/ldp#Resource>; rel="type"
Link: <http://www.w3.org/ns/ldp#BasicContainer>; rel="type"
Link: </alice/posts/.acl>; rel="acl"

Relation	Purpose
type	Resource type(s)
acl	Access control document
describedby	Metadata resource

Container Membership

How containers track members:

@prefix ldp: <http://www.w3.org/ns/ldp#> .

</alice/posts/> a ldp:BasicContainer ;
    ldp:contains </alice/posts/post1>,
                 </alice/posts/post2>,
                 </alice/posts/post3> .

LDP in Solid

Solid extends LDP with:

Addition	Purpose
WAC/ACP	Access control
Solid-OIDC	Authentication
Type Indexes	Data discovery
Notifications	Real-time updates

Comparison

Feature	LDP	Raw HTTP	WebDAV
RDF support	Native	None	None
Containers	Yes	No	Collections
Content negotiation	Yes	Manual	Limited
Standard	W3C	IETF	IETF

Implementation Support

Server	LDP Support
CSS	Full
NSS	Full
JSS	Full
ESS	Full

Links

• Specification: W3C LDP
• Primer: LDP Primer

See Also

• Solid Protocol — Built on LDP
• Linked Data — The data model
• CSS — LDP server implementation