specification: A repository from phochste

Exposing your Linked Datasets in hypermedia collections

ᴛʀᴇᴇ enables you to describe relations between a specific value and all members a page linked from this current page. Using this specific relation, a script or autonomous query client (such as Comunica and Planner.js) can understand whether following the link will be useful or not.

Build the spec using bikeshed:

bikeshed watch spec.bs

The spec will be built automatically when pushing to master.

The Vocabulary

Base URI to be used: https://w3id.org/tree#.

Preferred prefix: tree:.

All newly introduced terms are explained in the RDF vocabulary.

Most important concepts:

a tree:Node is a page that may contain members of a tree:Collection
a node has tree:relation entities with links to other nodes. This relation is typed (e.g., tree:GeospatiallyContainsRelation or a tree:PrefixRelation),
the relation has a tree:value and a tree:path. The former is a literal value on which the search term can be compared. The tree:path explains to which property of the members of the collection this relation applies.

The specification

Available at https://treecg.github.io/specification

Mind that a server exposing data with ᴛʀᴇᴇ must set the CORS headers to allow any host.

Questions and Answers

Why publish a hypermedia structure?

When a document grows too large for 1 HTTP response, we need to fragment it. The way we fragment it will immediatly decide what queries will be fast and which queries will be slow. Hypermedia can be used to hit the sweet spot between data dumps and querying APIs (such as GraphQL or SPARQL). It is particularly a sweet spot for Open Data publishers that need a cost-efficient way of publishing their data, while allowing third parties to create serverless applications to reuse the data.

	dump	ᴛʀᴇᴇ fragments	query
processing	client	shared	server
server cost	low	okay	high
client cost	high	okay	low
caching	low	high	low
query execution control	high	high	low

Why hypermedia?

When you write a client for one server, you can get away with hard-coding the way the API is built based on the API specification. When building a client for the entire Web, we need to make very general specifications that still allow our client to understand what it can do next. The latter are called the hypermedia controls.

What are triples? JSON-LD? RDF? URIs? Linked Data?