add example for Optionals Order Dependent Queries in sparql tutorial (#50)
diff --git a/source/tutorials/sparql_optionals.md b/source/tutorials/sparql_optionals.md
index dcc19d0..8a6bb07 100644
--- a/source/tutorials/sparql_optionals.md
+++ b/source/tutorials/sparql_optionals.md
@@ -146,11 +146,59 @@
If the first optional binds `?name` and `?x` to some values, the
second `OPTIONAL` is an attempt to match the ground triples (`?x`
-and `<kbd>?name</kbd>` have values). If the first optional did not
+and `?name` have values). If the first optional did not
match the optional part, then the second one is an attempt to match
its triple with two variables.
-
+With an example set of data in which every combination of values exist:
+
+```xml
+<rdf:RDF
+ xmlns:rdf='http://www.w3.org/1999/02/22-rdf-syntax-ns#'
+ xmlns:vCard='http://www.w3.org/2001/vcard-rdf/3.0#'
+ xmlns:info='http://somewhere/peopleInfo#'
+ xmlns:foaf='http://xmlns.com/foaf/0.1/'
+ >
+
+ <!-- both vCard:FN and foaf:name have values, and the values are the same -->
+ <foaf:Person rdf:about="http://somewhere/JohnSmith">
+ <vCard:FN>John Smith</vCard:FN>
+ <foaf:name>John Smith</foaf:name>
+ </foaf:Person>
+
+ <!-- both vCard:FN and foaf:name have values, but the values are not the same -->
+ <foaf:Person rdf:about="http://somewhere/RebeccaSmith">
+ <vCard:FN>Becky Smith</vCard:FN>
+ <foaf:name>Rebecca Smith</foaf:name>
+ </foaf:Person>
+
+ <!-- only vCard:FN has values -->
+ <foaf:Person rdf:about="http://somewhere/SarahJones">
+ <vCard:FN>Sarah Jones</vCard:FN>
+ </foaf:Person>
+
+ <!-- only foaf:name has values -->
+ <foaf:Person rdf:about="http://somewhere/MattJones">
+ <foaf:name>Matthew Jones</foaf:name>
+ </foaf:Person>
+
+ <!-- neither vCard:FN nor foaf:name have values -->
+ <foaf:Person rdf:about="http://somewhere/AdamJones" />
+
+</rdf:RDF>
+```
+
+Executing the above query will yield these solutions:
+
+ -------------------
+ | name |
+ ===================
+ | "John Smith" |
+ | "Matthew Jones" |
+ | "Sarah Jones" |
+ | |
+ | "Rebecca Smith" |
+ -------------------
[Next: union queries](sparql_union.html)
