update RDF example

rdf/RDF.ipynb

@@ -89,7 +89,7 @@
     "editable": false,
     "nbgrader": {
      "cell_type": "markdown",
-     "checksum": "5c2cccdf6463262a0f8bc89c64f97fb2",
+     "checksum": "27164b58076ba5ec8929d9652528a1bb",
      "grade": false,
      "grade_id": "cell-d8db3c16cee92ac1",
      "locked": true,
@@ -143,7 +143,15 @@
     "\n",
     "In the exercises, we will be using turtle notation, because it is very readable.\n",
     "\n",
-    "Here's an example of document in Turtle, taken from the Turtle specification:\n",
+    "For instance, turtle allows us to re-use parts of a previous triple to avoid repetition.\n",
+    "Our previous example would look like this:\n",
+    "\n",
+    "```turtle\n",
+    "<http://example.org/Timmy>  <http://example.org/hasDog> <http://example.org/Tobby> ;\n",
+    "                            <http://example.org/age> 7\n",
+    "```\n",
+    "\n",
+    "Here's another example of document in Turtle, taken from the Turtle specification:\n",
     "\n",
     "```turtle\n",
     "@base <http://example.org/> .\n",
@@ -152,15 +160,13 @@
     "@prefix foaf: <http://xmlns.com/foaf/0.1/> .\n",
     "@prefix rel: <http://www.perceive.net/schemas/relationship/> .\n",
     "\n",
-    "<#green-goblin>\n",
-    "    rel:enemyOf <#spiderman> ;\n",
-    "    a foaf:Person ;    # in the context of the Marvel universe\n",
-    "    foaf:name \"Green Goblin\" .\n",
+    "<#green-goblin> a foaf:Person ;             # Green Goblin is a person (in the universe of Marvel)\n",
+    "                foaf:name \"Green Goblin\" ;\n",
+    "                rel:enemyOf <#spiderman> .  # Green Goblin is one of Spiderman's enemy \n",
     "\n",
-    "<#spiderman>\n",
-    "    rel:enemyOf <#green-goblin> ;\n",
-    "    a foaf:Person ;\n",
-    "    foaf:name \"Spiderman\", \"Человек-паук\"@ru .\n",
+    "<#spiderman> a foaf:Person ;  # Spiderman is also a person\n",
+    "             foaf:name \"Spiderman\", \"Человек-паук\"@ru .  # Spiderman's name in Russian is Человек-паук\n",
+    "             rel:enemyOf <#green-goblin> ; \n",
     "```\n",
     "\n",
     "\n",