[tracker/wip/carlosg/some-docs: 3/3] docs: Add first couple of chapters for SPARQL tutorial
- From: Carlos Garnacho <carlosg src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [tracker/wip/carlosg/some-docs: 3/3] docs: Add first couple of chapters for SPARQL tutorial
- Date: Mon, 27 Apr 2020 22:03:41 +0000 (UTC)
commit 73113a6c66be25ca0fb62233fde7c39017bef0c9
Author: Carlos Garnacho <carlosg gnome org>
Date: Mon Apr 27 18:48:49 2020 +0200
docs: Add first couple of chapters for SPARQL tutorial
.../libtracker-sparql/images/triple-graph-1.dia | Bin 0 -> 1189 bytes
.../libtracker-sparql/images/triple-graph-1.png | Bin 0 -> 3140 bytes
.../libtracker-sparql/images/triple-graph-2.dia | Bin 0 -> 2774 bytes
.../libtracker-sparql/images/triple-graph-2.png | Bin 0 -> 26803 bytes
.../libtracker-sparql/images/triple-graph-3.dia | Bin 0 -> 1707 bytes
.../libtracker-sparql/images/triple-graph-3.png | Bin 0 -> 8628 bytes
.../libtracker-sparql/libtracker-sparql-docs.xml | 1 +
docs/reference/libtracker-sparql/meson.build | 8 +-
docs/reference/libtracker-sparql/tutorial.xml | 326 +++++++++++++++++++++
9 files changed, 334 insertions(+), 1 deletion(-)
---
diff --git a/docs/reference/libtracker-sparql/images/triple-graph-1.dia
b/docs/reference/libtracker-sparql/images/triple-graph-1.dia
new file mode 100644
index 000000000..d423640a9
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diff --git a/docs/reference/libtracker-sparql/images/triple-graph-1.png
b/docs/reference/libtracker-sparql/images/triple-graph-1.png
new file mode 100644
index 000000000..94ff24b9a
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diff --git a/docs/reference/libtracker-sparql/images/triple-graph-2.dia
b/docs/reference/libtracker-sparql/images/triple-graph-2.dia
new file mode 100644
index 000000000..b65d3b07b
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diff --git a/docs/reference/libtracker-sparql/images/triple-graph-2.png
b/docs/reference/libtracker-sparql/images/triple-graph-2.png
new file mode 100644
index 000000000..f199a07c3
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diff --git a/docs/reference/libtracker-sparql/images/triple-graph-3.dia
b/docs/reference/libtracker-sparql/images/triple-graph-3.dia
new file mode 100644
index 000000000..d6171659f
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diff --git a/docs/reference/libtracker-sparql/images/triple-graph-3.png
b/docs/reference/libtracker-sparql/images/triple-graph-3.png
new file mode 100644
index 000000000..cd4b97d84
Binary files /dev/null and b/docs/reference/libtracker-sparql/images/triple-graph-3.png differ
diff --git a/docs/reference/libtracker-sparql/libtracker-sparql-docs.xml
b/docs/reference/libtracker-sparql/libtracker-sparql-docs.xml
index 64b72e3ec..e0d6c1b3e 100644
--- a/docs/reference/libtracker-sparql/libtracker-sparql-docs.xml
+++ b/docs/reference/libtracker-sparql/libtracker-sparql-docs.xml
@@ -55,6 +55,7 @@
<xi:include href="performance.xml"/>
<xi:include href="migrating-1to2.xml"/>
<xi:include href="migrating-2to3.xml"/>
+ <xi:include href="tutorial.xml"/>
<index id="api-index-full">
<title>Index</title>
diff --git a/docs/reference/libtracker-sparql/meson.build b/docs/reference/libtracker-sparql/meson.build
index f85a17bce..9ae4893ac 100644
--- a/docs/reference/libtracker-sparql/meson.build
+++ b/docs/reference/libtracker-sparql/meson.build
@@ -28,6 +28,12 @@ example_files = [
'examples/writeonly-with-blank-nodes-example.c',
]
+image_files = [
+ 'images/triple-graph-1.png',
+ 'images/triple-graph-2.png',
+ 'images/triple-graph-3.png',
+]
+
private_headers = [
'tracker-notifier-private.h',
]
@@ -37,7 +43,7 @@ gnome.gtkdoc('libtracker-sparql',
main_xml: 'libtracker-sparql-docs.xml',
scan_args: ['--ignore-headers=' + ' '.join(private_headers)],
content_files: ['overview.xml', 'examples.xml', 'ontologies.xml', 'private-store.xml',
'migrating-1to2.xml', example_files],
- html_assets: icon_images,
+ html_assets: image_files,
gobject_typesfile: 'libtracker-sparql.types',
dependencies: tracker_sparql_dep,
fixxref_args: fixxref_args,
diff --git a/docs/reference/libtracker-sparql/tutorial.xml b/docs/reference/libtracker-sparql/tutorial.xml
new file mode 100644
index 000000000..94221dcdd
--- /dev/null
+++ b/docs/reference/libtracker-sparql/tutorial.xml
@@ -0,0 +1,326 @@
+<?xml version='1.0' encoding="ISO-8859-1"?>
+<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
+ "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd"; [
+<!ENTITY % local.common.attrib "xmlns:xi CDATA #FIXED 'http://www.w3.org/2001/XInclude'">
+]>
+
+<part id="tracker-tutorial">
+ <title>SPARQL tutorial</title>
+ <partintro>
+ <para>
+ This tutorial aims to introduce you to RDF and SPARQL from the ground
+ up. All examples come from the Nepomuk ontology, and even though the
+ tutorial aims to be generic enough, it mentions things specific to
+ Tracker, those are clearly spelled out.
+ </para>
+ </partintro>
+
+ <chapter id="tracker-tutorial-rdf-triples">
+ <title>RDF Triples</title>
+ <para>
+ RDF data define a graph, composed by vertices and edges. This graph is
+ directed, because edges point from one vertex to another, and it is
+ labeled, as those edges have a name. The unit of data in RDF is a
+ triple of the form:
+ <informalexample>
+ <programlisting>
+ subject predicate object
+ </programlisting>
+ </informalexample>
+
+ Or expressed visually:
+ <graphic fileref="triple-graph-1.png" format="PNG"></graphic>
+ </para>
+ <para>
+ Subject and object are 2 graph vertices and the predicate is the edge,
+ the accumulation of those triples form the full graph. For example,
+ the following triples:
+ <informalexample>
+ <programlisting>
+<a> a nfo:FileDataObject .
+<a> a nmm:MusicPiece .
+<a> nie:title "Images" .
+<a> nmm:musicAlbum <b> .
+<a> nmm:albumArtist <c> .
+<a> nmm:albumArtist <d> .
+<a> nmm:performer <e> .
+<b> a nmm:MusicAlbum .
+<b> nie:title "Go Off!" .
+<c> a nmm:Artist .
+<c> nmm:artistName "Jason Becker" .
+<d> a nmm:Artist .
+<d> nmm:artistName "Marty Friedman" .
+<e> a nmm:Artist .
+<e> nmm:artistName "Cacophony" .
+ </programlisting>
+ </informalexample>
+ Would visually generate the following graph:
+ <graphic fileref="triple-graph-2.png" format="PNG"></graphic>
+ </para>
+ <para>
+ The dot after each triple is not (just) there for legibility, but is
+ part of the syntax. The RDF triples in full length are quite repetitive
+ and cumbersome to write, luckily they can be shortened by providing multiple
+ objects (with <systemitem>,</systemitem> separator) or multiple predicate/object
+ pairs (with <systemitem>;</systemitem> separator), the previous RDF could be
+ transformed into:
+ <informalexample>
+ <programlisting>
+<a> a nfo:FileDataObject, nmm:MusicPiece .
+<a> nie:title "Images" .
+<a> nmm:musicAlbum <b> .
+<a> nmm:albumArtist <c> , <d> .
+<a> nmm:performer <e> .
+<b> a nmm:MusicAlbum .
+<b> nie:title "Go Off!" .
+<c> a nmm:Artist .
+<c> nmm:artistName "Jason Becker" .
+<d> a nmm:Artist .
+<d> nmm:artistName "Marty Friedman" .
+<e> a nmm:Artist .
+<e> nmm:artistName "Cacophony" .
+ </programlisting>
+ </informalexample>
+ And further into:
+ <informalexample>
+ <programlisting>
+<a> a nfo:FileDataObject, nmm:MusicPiece ;
+ nie:title "Images" ;
+ nmm:musicAlbum <b> ;
+ nmm:albumArtist <c>, <d> ;
+ nmm:performer <e> .
+<b> a nmm:MusicAlbum ;
+ nie:title "Go Off!" .
+<c> a nmm:Artist ;
+ nmm:artistName "Jason Becker" .
+<d> a nmm:Artist ;
+ nmm:artistName "Marty Friedman" .
+<e> a nmm:Artist ;
+ nmm:artistName "Cacophony" .
+ </programlisting>
+ </informalexample>
+ </para>
+ </chapter>
+
+ <chapter id="tracker-tutorial-sparql">
+ <title>SPARQL</title>
+ <para>
+ SPARQL defines a query language for RDF data. How does a query language
+ for graphs work? Naturally by providing a graph to be matched, it is
+ conveniently called the "graph pattern".
+ </para>
+ <para>
+ To begin simple, the simplest query would consist of a triple with all
+ 3 elements defined, e.g.:
+ <informalexample>
+ <programlisting language="SPARQL">
+ASK { <a> nie:title "Images" }
+ </programlisting>
+ </informalexample>
+ </para>
+ <para>
+ Which would result in <systemitem>true</systemitem>, as the triple does
+ exist. The ASK query syntax is actually the simplest form of graph
+ testing, resulting in a single boolean row/column containing whether
+ the provided graph exists in the store or not. It also works for more
+ complex graphs, for example:
+
+ <informalexample>
+ <programlisting language="SPARQL">
+ASK { <a> nie:title "Images" ;
+ nmm:albumArtist <c> ;
+ nmm:musicAlbum <b> .
+ <b> nie:title "Go Off!" .
+ <c> nmm:artistName "Jason Becker" }
+ </programlisting>
+ </informalexample>
+ </para>
+ <para>
+ But of course the deal of a query language is being able to obtain
+ the stored data. The SELECT query syntax is used for that, and variables
+ are denoted with a '?' prefix, variables act as "placeholders" where any
+ data will match and be available to the resultset or within the query as
+ that variable name. The following query would be the opposite to the
+ first ASK query:
+
+ <informalexample>
+ <programlisting language="SPARQL">
+SELECT * { ?subject ?predicate ?object }
+ </programlisting>
+ </informalexample>
+ </para>
+ <para>
+ What does this query do? it provides a triple with 3 variables, that
+ every known triple in the database will match. The '*' is a shortcut for
+ all queried variables, the query could also be expressed as:
+
+ <informalexample>
+ <programlisting language="SPARQL">
+SELECT ?subject ?predicate ?object { ?subject ?predicate ?object }
+ </programlisting>
+ </informalexample>
+ </para>
+ <para>
+ However, querying for all known data is most often hardly useful, this
+ got unwieldly soon! Luckily, that is not necessarily the case, the variables
+ may be used anywhere in the triple definition, with other triple elements
+ consisting of literals you want to match for, e.g.:
+
+ <example>
+ <title>
+ Give me the title of resource <systemitem><a></systemitem> (Result: "Images").
+ </title>
+ <programlisting language="SPARQL">
+SELECT ?songName { <a> nie:title ?songName }
+ </programlisting>
+ </example>
+
+ <example>
+ <title>
+ What is this text to <b>? (Result: the nie:title)
+ </title>
+ <programlisting language="SPARQL">
+SELECT ?predicate { <b> ?predicate "Go Off!" }
+ </programlisting>
+ </example>
+
+ <example>
+ <title>
+ What is the resource URI of this fine musician? (Result: <systemitem><d></systemitem>)
+ </title>
+ <programlisting language="SPARQL">
+SELECT ?subject { ?subject nmm:artistName "Marty Friedman" }
+ </programlisting>
+ </example>
+
+ <example>
+ <title>
+ Give me all resources that are a music piece (Result: <systemitem><a></systemitem>)
+ </title>
+ <programlisting language="SPARQL">
+SELECT ?song { ?song a nmm:MusicPiece }
+ </programlisting>
+ </example>
+ </para>
+ <para>
+ And also combinations of them, for example:
+
+ <example>
+ <title>
+ Give me all predicate/object pairs for resource <systemitem><a></systemitem>
+ </title>
+ <programlisting language="SPARQL">
+SELECT ?pred ?obj { <a> ?pred ?obj }
+ </programlisting>
+ </example>
+
+ <example>
+ <title>
+ <quote>The Answer to the Ultimate Question of Life, the Universe, and Everything</quote>
+ </title>
+ <programlisting language="SPARQL">
+SELECT ?subj ?pred { ?subj ?pred 42 }
+ </programlisting>
+ </example>
+
+ <example>
+ <title>
+ Give me all resources that have a title, and their title.
+ </title>
+ <programlisting language="SPARQL">
+SELECT ?subj ?obj { ?subj nie:title ?obj }
+ </programlisting>
+ </example>
+
+ And of course, the graph pattern can hold more complex triple
+ definitions, that will be matched as a whole across the stored
+ data. for example:
+
+ <example>
+ <title>
+ Give me all songs from this fine album
+ </title>
+ <programlisting language="SPARQL">
+SELECT ?song { ?album nie:title "Go Off!" .
+ ?song nmm:musicAlbum ?album }
+ </programlisting>
+ </example>
+
+ <example>
+ <title>
+ Give me all song resources, their title, and their album title
+ </title>
+ <programlisting language="SPARQL">
+SELECT ?song ?songTitle ?albumTitle { ?song a nmm:MusicPiece ;
+ nmm:musicAlbum ?album ;
+ nie:title ?songTitle .
+ ?album nie:title ?albumTitle }
+ </programlisting>
+ </example>
+ </para>
+ <para>
+ Stop a bit to think on the graph pattern expressed in the last query:
+ <graphic fileref="triple-graph-3.png" format="PNG"></graphic>
+ </para>
+ <para>
+ This pattern on one hand consists of specified data (eg. ?song must
+ be a <systemitem>nmm:MusicPiece</systemitem>, it must have a
+ <systemitem>nmm:musicAlbum</systemitem> and a <systemitem>nie:title</systemitem>,
+ ?album must have a <systemitem>nie:title</systemitem>), which must all
+ apply for a match to happen.
+ </para>
+ <para>
+ On the other hand, the graph pattern contains a number of variables,
+ some only used internally in the graph pattern, as a temporary
+ variable of sorts (?album, in order to express the relation between
+ ?song and its album title), while other variables are requested in
+ the result set.
+ </para>
+ </chapter>
+
+ <!-- FIXME: Keep writing! -->
+ <!--
+ <chapter id="tracker-tutorial-ontologies">
+ <title>Ontologies</title>
+ </chapter>
+ <chapter id="tracker-tutorial-inserting-data">
+ <title>Inserting data</title>
+ </chapter>
+ <chapter id="tracker-tutorial-updates-deletes">
+ <title>Updates and deletes</title>
+ </chapter>
+ <chapter id="tracker-tutorial-named-nodes">
+ <title>Named nodes</title>
+ </chapter>
+ <chapter id="tracker-tutorial-blank-nodes">
+ <title>Blank nodes</title>
+ </chapter>
+ <chapter id="tracker-tutorial-property-paths">
+ <title>Property paths</title>
+ </chapter>
+ <chapter id="tracker-tutorial-optional">
+ <title>Optional data</title>
+ </chapter>
+ <chapter id="tracker-tutorial-filtering">
+ <title>Filtering data</title>
+ </chapter>
+ <chapter id="tracker-tutorial-binding">
+ <title>Binding expressions to variables</title>
+ </chapter>
+ <chapter id="tracker-tutorial-aggregates">
+ <title>Aggregates</title>
+ </chapter>
+ <chapter id="tracker-tutorial-graphs">
+ <title>Graphs</title>
+ </chapter>
+ <chapter id="tracker-tutorial-services">
+ <title>Services</title>
+ </chapter>
+ <chapter id="tracker-tutorial-import-export">
+ <title>Importing and exporting data</title>
+ </chapter>
+ <chapter id="tracker-tutorial-graph-management">
+ <title>Graph Management</title>
+ </chapter>
+ -->
+</part>
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