Describing LDP Applications with the Hydra Core Vocabulary
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The document describes how to model an address book application using the Linked Data Platform (LDP) and Hydra Core Vocabularies. It provides examples of modeling an address book container and contacts as LDP resources, supporting common operations like GET, POST and PATCH. It also shows how to describe the application's API using the Hydra Core Vocabulary, including supported classes, operations and documentation. Potential conflicts between LDP and Hydra concepts like containers vs collections and paging are discussed.
![LDP Container - POST
13Nandana Mihindukulasooriya, OEG
POST /nandana/contacts/ HTTP/1.1
Host: example.org
Slug: jane
Link: <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:jane@example.com>;
vcard:fn “Jane Doe";
vcard:hasTelephone [ a vcard:Home, vcard:Voice;
vcard:hasValue <tel:+34655555555> ] .
expected Input
(vocabulary,
cardinalities)
supports Slug header](https://image.slidesharecdn.com/ldp-hydra-api-salad2015-150601143936-lva1-app6892/85/Describing-LDP-Applications-with-the-Hydra-Core-Vocabulary-13-320.jpg)
![API Documentation
21Nandana Mihindukulasooriya, OEG
{
"@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",
…
},
….
],
…](https://image.slidesharecdn.com/ldp-hydra-api-salad2015-150601143936-lva1-app6892/85/Describing-LDP-Applications-with-the-Hydra-Core-Vocabulary-21-320.jpg)
![API Documentation
22Nandana Mihindukulasooriya, OEG
{
"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": [
…
]
},](https://image.slidesharecdn.com/ldp-hydra-api-salad2015-150601143936-lva1-app6892/85/Describing-LDP-Applications-with-the-Hydra-Core-Vocabulary-22-320.jpg)
![API Documentation
23Nandana Mihindukulasooriya, OEG
{
"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": [
…
]
},](https://image.slidesharecdn.com/ldp-hydra-api-salad2015-150601143936-lva1-app6892/85/Describing-LDP-Applications-with-the-Hydra-Core-Vocabulary-23-320.jpg)
![Hydra PagedCollection
29Nandana Mihindukulasooriya, OEG
@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 ...
]
}](https://image.slidesharecdn.com/ldp-hydra-api-salad2015-150601143936-lva1-app6892/85/Describing-LDP-Applications-with-the-Hydra-Core-Vocabulary-29-320.jpg)
Describing LDP Applications with the Hydra Core Vocabulary
- 1. 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 2Nandana Mihindukulasooriya, OEG
- 3. An example application 3Nandana Mihindukulasooriya, OEG • 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 4Nandana Mihindukulasooriya, OEG Address Book Application Address Book Client
- 5. Domain Model 5Nandana Mihindukulasooriya, OEG AddressBook Contact •email •fullName •telephone •url User •name •title Schema Restrictions • Data types • Cardinalities
- 6. LDP Model 6Nandana Mihindukulasooriya, OEG «BasicContainer» AddressBook /{personId}/contacts/ «LDPResource» Contact ldp:contains /{personId}/contacts/{contactId} «LDPResource» User /{personId}/ foaf: primaryTopic vcard:Email vcard:Voice rdfs:Resource vcard:hasURL xsd:string vcard:hasEmail vcard:hasTelephone vcard:fn xsd:string foaf:name
- 7. Application 7Nandana Mihindukulasooriya, OEG Address Book Application Address Book Client
- 8. LDP Container - GET 8Nandana Mihindukulasooriya, OEG GET /alice/contacts/ HTTP/1.1 Host: example.org Accept: text/turtle HTTP/1.1 200 OK Content-Type: text/turtle; charset=UTF-8 Link: <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, POST Accept-Post: text/turtle, application/ld+json Content-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 9Nandana Mihindukulasooriya, OEG GET /alice/contacts/ HTTP/1.1 Host: example.org Accept: text/turtle HTTP/1.1 200 OK Content-Type: text/turtle; charset=UTF-8 Link: <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, POST Accept-Post: text/turtle Content-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> . supports LDP Basic Container interactions
- 10. LDP Container - GET 10Nandana Mihindukulasooriya, OEG GET /alice/contacts/ HTTP/1.1 Host: example.org Accept: text/turtle HTTP/1.1 200 OK Content-Type: text/turtle; charset=UTF-8 Link: <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, POST Accept-Post: text/turtle, application/ld+json Content-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> . supports the mentioned HTTP operations on this resource
- 11. LDP Container - GET 11Nandana Mihindukulasooriya, OEG GET /alice/contacts/ HTTP/1.1 Host: example.org Accept: text/turtle HTTP/1.1 200 OK Content-Type: text/turtle; charset=UTF-8 Link: <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, POST Accept-Post: text/turtle, application/ld+json Content-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> . Turtle and JSON-LD media types are accepted on POST
- 13. LDP Container - POST 13Nandana Mihindukulasooriya, OEG POST /nandana/contacts/ HTTP/1.1 Host: example.org Slug: jane Link: <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:jane@example.com>; vcard:fn “Jane Doe"; vcard:hasTelephone [ a vcard:Home, vcard:Voice; vcard:hasValue <tel:+34655555555> ] . expected Input (vocabulary, cardinalities) supports Slug header
- 14. LDP Container - GET 14Nandana Mihindukulasooriya, OEG GET /alice/contacts/ HTTP/1.1 Host: example.org Accept: text/turtle HTTP/1.1 200 OK Content-Type: text/turtle; charset=UTF-8 Link: <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, POST Accept-Post: text/turtle, application/ld+json Accept-Patch: text/ldpatch Content-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> . Hypermedia controls
- 16. LDP Container - GET 16Nandana Mihindukulasooriya, OEG GET /alice/contacts/ HTTP/1.1 Host: example.org Accept: application/vnd.ldp.addressbook+turtle HTTP/1.1 200 OK Content-Type: application/vnd.ldp.addressbook+turtle; charset=UTF-8 Link: <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, POST Accept-Post: application/vnd.ldp.contact+turtle; Accept-Patch: text/ldpatch Content-Length: 250 @prefix ldp: <http://xmlns.com/foaf/0.1/> . @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> .
- 17. LDP Container V1 - GET 17Nandana Mihindukulasooriya, OEG GET /alice/contacts/ HTTP/1.1 Host: example.org Accept: application/vnd.ldp.addressbook.v1+turtle HTTP/1.1 200 OK Content-Type: application/vnd.ldp.addressbook.v1+turtle; charset=UTF-8 Link: <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, POST Accept-Post: application/vnd.ldp.contact.v1+turtle; Accept-Patch: text/ldpatch Content-Length: 250 @prefix ldp: <http://xmlns.com/foaf/0.1/> . @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> .
- 19. Hydra Core Vocabulary 19Nandana Mihindukulasooriya, OEG
- 20. LDP Container – GET /w Hydra API Link relation 20Nandana Mihindukulasooriya, OEG HTTP/1.1 200 OK Content-Type: text/turtle; charset=UTF-8 Link: <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, POST Accept-Post: text/turtle, application/ld+json Accept-Patch: text/ldpatch Content-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> .
- 21. API Documentation 21Nandana Mihindukulasooriya, OEG { "@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", … }, …. ], …
- 22. API Documentation 22Nandana Mihindukulasooriya, OEG { "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 23Nandana Mihindukulasooriya, OEG { "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": [ … ] },
- 24. API Documentation 24Nandana Mihindukulasooriya, OEG { "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, },
- 25. Potential Conflicts • Similar concepts in LDP and Hydra • LDP Containers Vs Hydra Collections • LDP Paging Vs Hydra Paged Collections 25Nandana Mihindukulasooriya, OEG
- 26. Collections vs Containers 26Nandana Mihindukulasooriya, OEG @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> .
- 27. Hydra collection as an LDP Direct Container 27Nandana Mihindukulasooriya, OEG @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> ;
- 28. LDP Paging 28Nandana Mihindukulasooriya, OEG GET /nandana?page2 HTTP/1.1 Host: example.org Accept: text/turtle Prefer: return=representation; max-triple-count="500" HTTP/1.1 200 OK Content-Type: text/turtle ETag: "_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
- 29. Hydra PagedCollection 29Nandana Mihindukulasooriya, OEG @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 ... ] }
- 30. 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 30Nandana Mihindukulasooriya, OEG