Merge pull request #4 from e-e-e/sparql

Add SPARQL query interface

Author: e-e-e

index.js

@@ -3,6 +3,7 @@ const stream = require('readable-stream')
 const pump = require('pump')
 const inherits = require('inherits')
 const events = require('events')
+const SparqlIterator = require('sparql-iterator')
 
 const utils = require('./lib/utils')
 const Variable = require('./lib/Variable')
@@ -122,6 +123,14 @@ Graph.prototype.search = function (query, options, callback) {
   utils.collect(this.searchStream(query, options), callback)
 }
 
+Graph.prototype.queryStream = function (query) {
+  return new SparqlIterator(query, { hypergraph: this })
+}
+
+Graph.prototype.query = function (query, callback) {
+  utils.collect(this.queryStream(query), callback)
+}
+
 Graph.prototype.generateBatch = utils.generateBatch
 
 Graph.prototype.close = function (callback) {

lib/utils.js

@@ -17,6 +17,15 @@ function collect (stream, cb) {
   stream.once('end', cb.bind(null, null, res))
 }
 
+function namespaceBlankVariables (triple) {
+  Object.keys(triple).forEach((key) => {
+    if (triple[key].startsWith && triple[key].startsWith('_:')) {
+      triple[key] = triple[key].replace(/^_:/, 'hypergraph:')
+    }
+  })
+  return triple
+}
+
 function filterTriple (triple) {
   const filtered = {}
   defs.spo.forEach((key) => {
@@ -58,7 +67,7 @@ function genKeys (triple) {
 function generateBatch (triple, action) {
   if (!action) action = 'put'
   var data = (action === 'put')
-    ? JSON.stringify(triple)
+    ? JSON.stringify(namespaceBlankVariables(triple))
     : null
   return genKeys(triple).map(key => ({
     type: 'put', // no delete in hyperdb so just puting nulls

package.json

@@ -14,7 +14,8 @@
     "hyperdb": "^2.0.0",
     "lru": "^3.1.0",
     "pump": "^2.0.0",
-    "readable-stream": "^2.3.3"
+    "readable-stream": "^2.3.3",
+    "sparql-iterator": "^2.0.5"
   },
   "devDependencies": {
     "chai": "^4.1.2",

readme.md

@@ -95,10 +95,21 @@ Allowed options:
 }
 ```
 
-#### `db.search(queries, [options], callback)`
+#### `db.query(query, callback)`
 
-Allows for Basic Graph Patterns searches where all queries must match.
-Expects queries to be an array of triple options of the form:
+Allows for querying the graph with [SPARQL](https://www.w3.org/TR/sparql11-protocol/) queries.
+Returns all entries that match the query.
+
+SPARQL queries are implemented using [sparql-iterator](https://github.com/e-e-e/sparql-iterator) - a fork of [Linked Data Fragments Client](https://github.com/LinkedDataFragments/Client.js).
+
+#### `var stream = db.queryStream(query)`
+
+Returns a stream of results from the SPARQL query.
+
+#### `db.search(patterns, [options], callback)`
+
+Allows for Basic Graph Patterns searches where all patterns must match.
+Expects patterns to be an array of triple options of the form:
 
 ```js
 {

test/data/simplefoaf.ttl

@@ -0,0 +1,7 @@
+@prefix  foaf:  <http://xmlns.com/foaf/0.1/> .
+
+_:a    foaf:givenname   "Alice" .
+_:a    foaf:family_name "Hacker" .
+
+_:b    foaf:firstname   "Bob" .
+_:b    foaf:surname     "Hacker" .

test/data/sparqlIn11Minutes.ttl

@@ -0,0 +1,25 @@
+@prefix vcard: <http://www.w3.org/2006/vcard/ns#> .
+@prefix sn: <http://www.snee.com/hr/> .
+
+sn:emp1   vcard:given-name   "Heidi" .
+sn:emp1   vcard:family-name   "Smith" .
+sn:emp1   vcard:title   "CEO" .
+sn:emp1   sn:hireDate   "2015-01-13" .
+sn:emp1   sn:completedOrientation   "2015-01-30" .
+
+sn:emp2   vcard:given-name   "John" .
+sn:emp2   vcard:family-name   "Smith" .
+sn:emp2   sn:hireDate   "2015-01-28" .
+sn:emp2   vcard:title   "Engineer" .
+sn:emp2   sn:completedOrientation   "2015-01-30" .
+sn:emp2   sn:completedOrientation   "2015-03-15" .
+
+sn:emp3   vcard:given-name   "Francis" .
+sn:emp3   vcard:family-name   "Jones" .
+sn:emp3   sn:hireDate   "2015-02-13" .
+sn:emp3   vcard:title   "Vice President" .
+
+sn:emp4   vcard:given-name   "Jane" .
+sn:emp4   vcard:family-name   "Berger" .
+sn:emp4   sn:hireDate   "1000-03-10" .
+sn:emp4   vcard:title   "Sales" .

test/queries/sparqlIn11Minutes1.rq

@@ -0,0 +1,7 @@
+PREFIX vcard: <http://www.w3.org/2006/vcard/ns#> 
+
+SELECT ?person 
+WHERE 
+{ 
+   ?person vcard:family-name "Smith" . 
+}

test/queries/sparqlIn11Minutes11.rq

@@ -0,0 +1,16 @@
+PREFIX vcard: <http://www.w3.org/2006/vcard/ns#> 
+PREFIX sn: <http://www.snee.com/hr/> 
+PREFIX foaf: <http://xmlns.com/foaf/0.1/>
+PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
+
+CONSTRUCT { 
+  ?person rdf:type foaf:Person . 
+  ?person foaf:givenName ?givenName .
+  ?person foaf:familyName ?familyName .
+  ?person foaf:name ?fullName .
+}
+WHERE { 
+  ?person vcard:given-name ?givenName .  
+  ?person vcard:family-name ?familyName .
+  BIND(concat(?givenName," ",?familyName) AS ?fullName) 
+}

test/queries/sparqlIn11Minutes2.rq

@@ -0,0 +1,8 @@
+PREFIX vcard: <http://www.w3.org/2006/vcard/ns#>
+
+SELECT ?person ?givenName
+WHERE
+{
+   ?person vcard:family-name "Smith" .
+   ?person vcard:given-name ?givenName .
+}

test/queries/sparqlIn11Minutes3.rq

@@ -0,0 +1,10 @@
+PREFIX vcard: <http://www.w3.org/2006/vcard/ns#> 
+PREFIX sn: <http://www.snee.com/hr/> 
+
+SELECT ?givenName ?familyName ?hireDate
+WHERE 
+{ 
+   ?person vcard:given-name ?givenName .
+   ?person vcard:family-name ?familyName . 
+   ?person sn:hireDate ?hireDate . 
+}