Destination tutorial for Ontop

This tutorial is adapted from the Virtual Knowledge Graph of the South Tyrolean Open Data Hub.

Materials

Slides of the tutorial given at the Knowledge Graph Conference (KGC) 2021 can be found in the slides directory.

The video of the tutorial is available here (subscription or conference ticket required).

Requirements

• Docker
• Protégé 5.5 with the Ontop 4.1.0 plugin installed. A bundle is available here.
• Optionally DBeaver or another database tool for visualizing the data source.

Clone this repository

On Windows

git clone https://github.com/ontopic-vkg/destination-tutorial  --config core.autocrlf=input

Otherwise, on MacOS and Linux:

git clone https://github.com/ontopic-vkg/destination-tutorial

Table of contents

• Setup Protégé
• Start Docker-Compose
• Dataset
• Mapping
• Solutions
• More info

Setup Protégé

• Run Protégé (run.bat on Windows, run.sh on Mac/Linux)
• Register the PostgreSQL JDBC driver: go to Preferences -> JDBC Drivers and add an entry with the following information
  • Description: postgresql
  • Class Name: org.postgresql.Driver
  • Driver file (jar): /path/to/destination-tutorial/jdbc/postgresql-42.2.8.jar
• Go to Reasoner and select Ontop 4.1.0 .

Start Docker-compose

• Go to the destination-tutorial repository
• Start the default Docker-compose file

docker-compose pull && docker-compose up

This command starts and initializes the database. Once the database is ready, it launches the SPARQL endpoint from Ontop at http://localhost:8080 .

For this tutorial, we assume that the ports 7777 (used for database) and 8080 (used by Ontop) are free. If you need to use different ports, please edit the file .env.

Dataset

The dataset is composed of the following tables:

• source1.municipalities

The table source1.municipalities contains the ID (m_id), name (en, it, de), Italian statistical institute code (istat) , population, geospatial coordinates (latitude, longitude, altitude) and geometrical point of municipalities.

m_id	istat	name_en	name_it	name_de	population	latitude	longitude	altitude	geometrypoint
A7CA017FF0424503 827BCD0E552F4648	021069	Proves/Proveis	Proves	Proveis	266	46.4781	11.023	1420.0	POINT Z(11.023 46.4781 1420)
BB0043517A574986 83B2F997B7B68D5F	021065	Ponte Gardena/Waidbruck	Ponte Gardena	Waidbruck	203	46.598	11.5317	470.0	POINT Z(11.5317 46.598 470)
516EF5F9F7794997 B874828DBE157E6E	021036	Glorenza/Glurns	Glorenza	Glurns	894	46.6711	10.5565	907.0	POINT Z(10.5565 46.6711 907)

The column m_id is the primary key.

• source1.hospitality

The table source1.hospitality contains the ID (h_id), name (en ,it ,de), telephone number, email, type (kind), geospatial coordinates (latitude, longitude, altitude), geometrical points and the associated municipality ID of lodging businesses.

h_id	name_en	name_it	name_de	telephone	email	kind	latitude	longitude	altitude	category	geometrypoint	m_id
ACE81868364111D4 9F0000105AF76E96	Apartments Monica	Appartamenti Monica	Appartements Monica	+39 380 4243160	[email protected]	BedBreakfast	46.9386	11.4444	1098.0	2suns	POINT Z(11.4444 46.9386 1098)	2B138D40992744BD BD38F56B73F45183
EFF0FACBA54C11D1 AD760020AFF92740	Residence Tuberis	Residence Tuberis	Residence Tuberis	+39 0474 678488	[email protected]	HotelPension	46.9191	11.9547	865.0	3stars	POINT Z(11.9547 46.9191 865)	6A5FF36917FA48D2 B1996B76C7AA8BC6
5F74DCC404AAA52B 318A12507A1F27F7	Camping Gisser Vitha Hotels	Camping Gisser Vitha Hotels	Camping Gisser Vitha Hotels	+39 0474 569605	[email protected]	Camping	46.807976	11.812105	778.0	3stars	POINT Z(11.812105 46.807976 778)	1E84922B82234EE6 82A341531E1D1925

The column kind is populated with the following values: Hotel, Hostel, Campground, Bed and Breakfast.

The column h_id is the primary key.

• source1.rooms

Similarly, the table source1.rooms contains the ID, name, number of units, maximal number of guests, multilingual descriptions and lodging business ID of accommodations (e.g. rooms and apartments).

r_id	name_en	name_it	name_de	room_units	type	guest_nb	description_de	description_it	h_id
E4B47698C5A67758 4245B6F4E13CCB69	Appartement "PANORMASUITE"	Apartment "Panoramasuite"	Appartamento "PANORMASUITE"	1	apartment	4	Natursuite mit Schlafempore...	Suite con area notte al piano superiore...	32001C4FAA1311D1 926F00805A150B0B
AF57632D700A11D3 962F00104B421FA8	"Crab apple"	"Zierapfel"	"Mela selvatica"	1	apartment	6	Wohnraum mit Kochnische...	Stanza di soggiorno con cucina...	E650C0C33DC111D2 9536004F56000ECA
65F7D5D3182D4300 A42E23D60F836F61	apartment Sella for 5-6 people	Ferienwohnung Sella für 5-6 Personen	Appartamento Sella per 5-6 persone	1	apartment	6	Ferienwohnung 5 Personen	Appartamento 5 persone	8DA75A1A0AE743B4 89948BA98ECA30A9

The column type is also populated with the following datatypes: Room, Appartement, Pitch, Youth.

The column r_id is the primary key.

• source2.hotels

The table source2.hotels has similar content to source1.hospitality, but with a different structure. It contains the ID, multilingual names (english, italian, german), type (htype), geospatial coordinates (lat, long, alt) rating value (cat), municipality ISTAT code (mun) and geometrical point (geom) of lodging businesses.

id	english	italian	german	htype	lat	long	alt	cat	mun	geom
001AE4C0FA0781A2C DD3750811DBDAEB	Apartment Haideblick	Appartamento Haideblick App.	Ferienwohnung Haideblick	1	46.766831	10.533657	1470.0	2suns	21027	POINT Z(10.533657 46.766831 1470)
0614E1C5699E11D7 82540020AF71A63E	House Rosi	Cafe/Casa Rosi	Cafe Ferienhaus Rosi	1	46.615587	10.699991	868.0	3suns	21042	POINT Z(10.699991 46.615587 868)
05287B29094E4B03 AD97A5B4B3E66345	Sonnenhof	Sonnenhof	Sonnenhof	3	46.706881	10.473704	1730.0	1flower	21046	POINT Z(10.473704 46.706881 1730)

The column htype is populated with magic numbers:

• 1 -> BedAndBreakfast
• 2 -> Hotel
• 3 -> Hostel
• 4 -> Campground

The column id is the primary key.

• source2.accommodation

The table source2.accommodation has similar content to source1.rooms, but with a different structure. An important difference is that it does not contain the number of units, which is implicitly equal to 1.

id	english_title	german_title	italian_title	acco_type	guest_nb	german_description	italian_description	hotel
73F2B6C02A6152C2 86BFF186D1572DBC	Apartment Zerminiger	Ferienwohnung Zerminiger	Appartamento Zerminiger	2	4	Mit einer Wohnfläche von 59 m² bietet...	Con una superficie abitabile di 59 mq...	0A99E8B00EBA5795 6959949D017055FB
7F90B92F9CAA2F65 3B0F4DAEF5476A67	Appartment for 2-6 persons	Ferienwohnung für 2-6 Personen	Appartamento per 2-6 persone	2	5	Großzügig ausgestatete geräumige Wohnung...	Ben aredate spazio appartamento...	25548AEDD4682E0D 809086AD1B28E6F2
D3B0D75E132711D2 91A60040055FA744	Family room	Doppelzimmer	Süd A mit Balkon & Talblick Camera famigliare	1	4	WC, Dusche, Balkon, Talblick	WC, doccia, balcone	F63F948FEE3E11D1 91A60040055FA744

The column acco_type is populated with magic numbers:

• 1 -> Room
• 2 -> Apartment
• 3 -> Pitch
• 4 -> Youth

The column id is the primary key.

• source3.weather_platforms

The table source3.weather_platforms contains the ID, name and geometrical point of weather platforms.

id	name	pointprojection
23862	Forte D'Ampola	POINT (10.646293 45.863893)
23863	Ghiacciaio Del Careser	POINT (10.718272 46.451278)
23864	Ghiacciaio di Fradusta	POINT (11.871709 46.255107)

• source3.weather_measurement

The table source3.weather_measurement contains the ID, validity period, timestamp, name and value of weather measurements. There is also the ID of the platform that performed the measurement.

id	period	timestamp	name	double_value	platform_id
203881	3600	2019-01-07 23:00:00	water-temperature	11.7	2173
204004	3600	2019-01-07 23:00:00	water-temperature	10.8	2166
230277	900	2020-07-14 14:15:00	wind10m_speed	4.5	23893

• source3.measurement_types

The table source3.measurement_types contains the name, unit, description and statistical type of measurements.

name	unit	description	statisticalType
temp_aria	[°C]	Temperatura dell’aria	Mean
umidita_rel	[%]	Umidità relativa dell’aria	Mean
umidita_abs	[g/m^3]	Umidità assoluta dell’aria	Mean

Optional: visualize it in DBeaver

To visualize the dataset in DBeaver or a similar tool, we need to create a database connection. In DBeaver, one can follow the next steps: Database -> New Database Connection -> PostgreSQL

The credentials to access the PostgreSQL database are the followings:

• Host: localhost
• Port: 7777
• User: postgres
• Password: postgres2

Mapping

In this tutorial, the ontology and the SPARQL queries are already provided. We will focus on the mapping. Our goal is to reproduce the following diagrams.

For tables in the schemas source1 and source2:

For tables in the schema source3:

The initial mapping already includes an entry describing municipalities.

Open the project on Protégé

On Protégé, open (in a new window if requested) the ontology file vkg/dest.ttl. Go to the Ontop Mappings tab (if you don't see it, enable it in Windows -> Tabs) and to the Mapping manager sub-tab. One mapping entry called Municipality should be visible.

If you click of File -> Save, your changes will be saved and the Ontop SPARQL endpoint will be automatically restarted.

Mapping entries

See the dedicated page for specifying the mapping entries.

Solutions

First, stop the current docker-compose:

docker-compose stop

Then, specify the file by using -f :

docker-compose -f docker-compose.solution.yml up

This Docker-compose file uses the mapping vkg/dest-solution.obda.

You can see it in Protégé by opening the ontology vkg/dest-solution.ttl in a different window.

Example SPARQL queries are available at http://localhost:8080/ .

To know more

Visit the official website of Ontop https://ontop-vkg.org, which also provides a more detailed tutorial.