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Apply SPARQL to Query Results

Description

SPARQL (SPARQL Protocol and RDF Query Language - pronounced "sparkle") is an industry-standard query language designed to work with graph databases. It is similar in syntax to SQL.

You can use SPARQL queries on CM-Well in order to apply database operations to infotons, which are the type of "database records" that CM-Well provides.

A SPARQL query to CM-Well has two parts. The first part is a set of paths within CM-Well on which you want to run the SPARQL query. The "paths" are in fact regular queries to CM-Well, which produce a list of infotons. After retrieving this list, CM-Well applies the second part - the SPARQL query - to the list.

See Using SPARQL on CM-Well Infotons for detailed explanations and examples.

Syntax

URL: <cm-well-host>/_sp

REST verb: POST

Mandatory parameters: PATHS section, SPARQL section (see below)

Template:

<cm-well-host>/_sp 
    PATHS
    <CMWellPath with query parameters, one per line>
    <CMWellPath with query parameters, one per line>
    <CMWellPath with query parameters, one per line>
    ...
    <empty line>
    SPARQL
    <SPARQL query - one or several separated by empty lines>

    <SPARQL query>

    <SPARQL query>
    ...

URL example: N/A

Curl example (REST API):

See Code Example.

Special Parameters

Each line in the PATHS section is a query to CM-Well, and its syntax is identical to that of a regular (non-SPARQL) query.

See CM-Well Query Parameters to learn more about CM-Well query syntax.

In addition, here are some special parameters you can add to a SPARQL query:

Parameter   Description
quads Returns RDF "quadruples" rather than "triples", meaning that in addition to the subject, predicate and object, it also returns the graph name for each triple.
verbose Returns the time-metrics of data retrieval and processing operations, as well as the data itself.
show-graph Shows the list of infotons, which are the result of the initial CM-Well query (and the input to the SPARQL query).

Code Example

Call

curl -X POST "<cm-well-host>/_sp?format=ascii" @curlInput.txt

File Contents

PATHS
    /example.org/Individuals?op=search&length=1000&with-data
    /example.org/Individuals/RonaldKhun
    /example.org/Individuals/JohnSmith?xg=3

    SPARQL
    SELECT DISTINCT ?name ?active WHERE { ?name <http://www.lbd.com/bold#active> ?active . } ORDER BY DESC(?active)

Note

The empty line between the end of the paths and the "SPARQL" header is mandatory.

Results

-------------------------------------------------------------
    | name| active  |
    =============================================================
    | <http://example.org/Individuals/BruceWayne> | "true"  |
    | <http://example.org/Individuals/DonaldDuck> | "true"  |
    | <http://example.org/Individuals/HarryMiller>| "true"  |
    | <http://example.org/Individuals/JohnSmith>  | "true"  |
    | <http://example.org/Individuals/MartinOdersky>  | "true"  |
    | <http://example.org/Individuals/NatalieMiller>  | "true"  |
    | <http://example.org/Individuals/PeterParker>| "true"  |
    | <http://example.org/Individuals/RonaldKhun> | "true"  |
    | <http://example.org/Individuals/SaraSmith>  | "true"  |
    | <http://example.org/Individuals/DaisyDuck>  | "false" |
    | <http://example.org/Individuals/RebbecaSmith>   | "false" |
    -------------------------------------------------------------

Note

  • Currently, the only SPARQL operations that CM-Well supports are SELECT and CONSTRUCT.
  • When referring to field names in SPARQL queries, you must use the full URI notation.
  • For SPARQL queries, you must use the header “Content Type: text/plain”.
  • If you need to include non-English characters in a SPARQL query (including the PATHS sections), add the Content Type: text/plain;charset=utf-8 header to the HTTP request. If you choose to URL-encode the non-English characters, make sure to encode all of them (don't mix URL-encoded and non-encoded characters in the same query). This is because once CM-Well detects URL-encoding, it will assume that all characters are URL-encoded.
  • Only the following output formats are supported for SPARQL queries: ascii, json, rdf, tsv, xml.
  • To learn how to upload and use SPARQL "stored procedures", see Using SPARQL on CM-Well Infotons.

Using SPARQL on CM-Well Infotons