describing ldp applications with the hydra core vocabulary

Describing LDP Applications with the Hydra Core Vocabulary

Nandana Mihindukulasooriya, and Raúl García-Castro

Ontology Engineering Group (OEG)

Facultad de Informática

Universidad Politécnica de Madrid

2

Linked Data Platform 1.0

Nandana Mihindukulasooriya, OEG

3

An example application


• An address book – for managing contacts• Contacts

• Create, List, Update, Delete• User

• Retrieve

Alice<<user>>

Alice’s Address Book Alice’s

Contacts

4

Address Book


Address BookApplication

Address BookClient

5

Domain Model


AddressBook Contact

•email •fullName•telephone•url

User

•name •title

Schema Restrictions• Data types• Cardinalities

6

LDP Model


«BasicContainer»AddressBook

/{personId}/contacts/

«LDPResource»Contact

ldp:contains

/{personId}/contacts/{contactId}

«LDPResource»User

/{personId}/

foaf:primaryTopic

vcard:Email

vcard:Voice

rdfs:Resourcevcard:hasURL

xsd:string

vcard:hasEmail

vcard:hasTelephone

vcard:fn

xsd:string

foaf:name

7

Application


Address BookApplication

Address BookClient

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LDP Container - GET


GET /alice/contacts/ HTTP/1.1Host: example.orgAccept: text/turtle

HTTP/1.1 200 OK Content-Type: text/turtle; charset=UTF-8Link: <http://www.w3.org/ns/ldp#BasicContainer>; rel='type', <http://www.w3.org/ns/ldp#Resource>; rel='type’ETag: W/'123456711'Allow: OPTIONS, HEAD, GET, POSTAccept-Post: text/turtle, application/ld+jsonContent-Length: 250

@prefix ldp: <http://www.w3.org/ns/ldp#> .@prefix dc: <http://purl.org/dc/terms/> .@prefix dc: <http://example.org/vocab#> .

<http://example.org/contacts/> a ex:AddressBook, ldp:BasicContainer; foaf:primaryTopic <http://example.org/alice>; ldp:contains <bob>, <jim> .

9

LDP Container - GET



HTTP/1.1 200 OK Content-Type: text/turtle; charset=UTF-8Link: <http://www.w3.org/ns/ldp#BasicContainer>; rel='type', <http://www.w3.org/ns/ldp#Resource>; rel='type’ETag: W/'123456711'Allow: OPTIONS, HEAD, GET, POSTAccept-Post: text/turtleContent-Length: 250



supports LDP Basic Container interactions

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LDP Container - GET






supports the mentioned HTTP operations on this resource

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LDP Container - GET






Turtle and JSON-LD media types are accepted on POST

12Nandana Mihindukulasooriya, OEG

http://kristenbloggen.net/wp-content/uploads/good.jpg

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LDP Container - POST


POST /nandana/contacts/ HTTP/1.1Host: example.orgSlug: janeLink: <http://www.w3.org/ns/ldp#Resource>; rel='type'Content-Type: text/turtle

@prefix vcard: <http://www.w3.org/2006/vcard/ns#> .

< > a ex:Contact, vcard:Individual; vcard:hasURL <http://example.org/jane#me> ; vcard:hasEmail <mailto:[email protected]>; vcard:fn “Jane Doe"; vcard:hasTelephone [ a vcard:Home, vcard:Voice; vcard:hasValue <tel:+34655555555> ] .

expected Input(vocabulary, cardinalities)

supports Slug header

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LDP Container - GET



HTTP/1.1 200 OK Content-Type: text/turtle; charset=UTF-8Link: <http://www.w3.org/ns/ldp#BasicContainer>; rel='type', <http://www.w3.org/ns/ldp#Resource>; rel='type’ETag: W/'123456711'Allow: OPTIONS, HEAD, GET, POSTAccept-Post: text/turtle, application/ld+jsonAccept-Patch: text/ldpatchContent-Length: 250



Hypermedia controls


http://www.teresacommunicates.com/wp-content/uploads/2014/01/i-can-do-this.jpg

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LDP Container - GET


GET /alice/contacts/ HTTP/1.1Host: example.orgAccept: application/vnd.ldp.addressbook+turtle

HTTP/1.1 200 OK Content-Type: application/vnd.ldp.addressbook+turtle; charset=UTF-8Link: <http://www.w3.org/ns/ldp#BasicContainer>; rel='type', <http://www.w3.org/ns/ldp#Resource>; rel='type’ETag: W/'123456711'Allow: OPTIONS, HEAD, GET, POSTAccept-Post: application/vnd.ldp.contact+turtle; Accept-Patch: text/ldpatchContent-Length: 250

@prefix ldp: <http://xmlns.com/foaf/0.1/> .@prefix dc: <http://purl.org/dc/terms/> .@prefix dc: <http://example.org/vocab#> .


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LDP Container V1 - GET


GET /alice/contacts/ HTTP/1.1Host: example.orgAccept: application/vnd.ldp.addressbook.v1+turtle

HTTP/1.1 200 OK Content-Type: application/vnd.ldp.addressbook.v1+turtle; charset=UTF-8Link: <http://www.w3.org/ns/ldp#BasicContainer>; rel='type', <http://www.w3.org/ns/ldp#Resource>; rel='type’ETag: W/'123456711'Allow: OPTIONS, HEAD, GET, POSTAccept-Post: application/vnd.ldp.contact.v1+turtle; Accept-Patch: text/ldpatchContent-Length: 250

@prefix ldp: <http://xmlns.com/foaf/0.1/> .@prefix dc: <http://purl.org/dc/terms/> .@prefix dc: <http://example.org/vocab#> .


19

Hydra Core Vocabulary


20

LDP Container – GET /w Hydra API Link relation


HTTP/1.1 200 OK Content-Type: text/turtle; charset=UTF-8Link: <http://www.w3.org/ns/ldp#BasicContainer>; rel=“type”,

<http://www.w3.org/ns/ldp#Resource>; rel=“type”Link: <http://example.com/doc/>; rel="http://www.w3.org/ns/hydra/core#apiDocumentation"ETag: W/'123456711'Allow: OPTIONS, HEAD, GET, POSTAccept-Post: text/turtle, application/ld+jsonAccept-Patch: text/ldpatchContent-Length: 250

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

<http://example.org/contacts/> a ldp:BasicContainer; foaf:primaryTopic <http://example.org/alice>; ldp:contains <bob>, <jim> .

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API Documentation


{ "@context": [ "http://www.w3.org/ns/hydra/context.jsonld", {…} ], "@id": "http://example.org/docs/", "@type": "ApiDocumentation", "title": "LDP Address Book API", "entrypoint": "http://example.org/contacts/", "supportedClass": [

{ "@id": "ex:AddressBook", "@type": "hydra:Class", "subClassOf": "ldp:BasicContainer", "label": "An example address book", … },….],

…

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API Documentation


{ "supportedClass": [

{ "@id": "ex:AddressBook", "@type": "hydra:Class", "subClassOf": "ldp:BasicContainer", "label": "An example address book", "supportedOperation": [ { "@id": "_:create_new_contact", "@type": "hydra:Operation", "method": "POST", "label": "creates a new contact in the address book", "description": null, "expects": “ex:Contact", "returns": null, "statusCodes": [ … ] },

23

API Documentation


{ "supportedClass": [

{ "@id": "ex:AddressBook", "@type": "hydra:Class", "subClassOf": "ldp:BasicContainer", "label": "An example address book", "supportedOperation": [ { "@id": "_:create_new_contact", "@type": "hydra:Operation", "method": "POST", "label": "creates a new contact in the address book", "description": null, "expects": “ex:Contact", "returns": null, "statusCodes": [ … ] },

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API Documentation


{ "supportedClass": [ …..

{ "@id": "ex:Contact", "@type": "hydra:Class", "subClassOf": “vcard:Individual", "label": “A contact", " supportedProperty": [ { "property": “vcard:hasEmail", "hydra:title": “Email”, "hydra:description": “Email of the contact", "required": true, "readable": true, "writable": false, },

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Potential Conflicts

• Similar concepts in LDP and Hydra

• LDP Containers Vs Hydra Collections

• LDP Paging Vs Hydra Paged Collections


26

Collections vs Containers


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

<http://example.org/alice/contacts> a hydra:Collection ; hydra:member <http://example.org/alice/contacts/bob>, <http://example.org/alice/contacts/jane> .

• Hydra Collection

• LDP Container

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

<http://example.org/alice/contacts> a ldp:BasicContainer ; ldp:contains <http://example.org/alice/contacts/bob>, <http://example.org/alice/contacts/jane> .

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Hydra collection as an LDP Direct Container


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

<http://example.org/alice/contacts> a hydra:Collection, ldp:DirectContainer; ldp:membershipResource <>; ldp:hasMemberRelation hydra:member;

ldp:contains <http://example.org/alice/contacts/bob>,<http://example.org/alice/contacts/jane> ;

hydra:member <http://example.org/alice/contacts/bob>, <http://example.org/alice/contacts/jane> ;

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LDP Paging


GET /nandana?page2 HTTP/1.1Host: example.orgAccept: text/turtlePrefer: return=representation; max-triple-count="500"

HTTP/1.1 200 OKContent-Type: text/turtleETag: "_87e52ce291112"Link: <http://www.w3.org/ns/ldp#Resource>; rel="type", <http://www.w3.org/ns/ldp#Page>; rel="type"Link: <http://example.org/alice/contacts?p=3>; rel="next"Link: <http://example.org/alice/contacts>; rel="canonical"; etag="_87e5"Link: <http://example.org/alice/contacts?page1>; rel="first"Link: <http://example.org/alice/contacts?p=4>; rel="last"Link: <http://example.org/alice/contacts?page1>; rel="prev"Allow: GET,OPTIONS,HEAD

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Hydra PagedCollection


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

{ "@context": "http://www.w3.org/ns/hydra/context.jsonld", "@id": "http://example.org/alice/contacts?page=3", "@type": "PagedCollection", "totalItems": “50", "itemsPerPage": "10", "firstPage": "http://example.org/alice/contacts?page=1", "nextPage": " http://example.org/alice/contacts?page=4", "previousPage": "http://example.org/alice/contacts?page=2", "lastPage": "http://example.org/alice/contacts?page=5", "member": [ ... the members of this PagedCollection ... ]}

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Conclusions

• LDP needs mechanisms for vocabulary and affordance discovery

• Hydra Core vocabulary can be used describe LDP application

• Why not just Hydra?

• There are overlaps in some areas

• Overlaps with the W3C RDF Shapes WG


describing ldp applications with the hydra core vocabulary

Technology