Squerall-GUI

Squerall-GUI is the user interface of Squerall --a solution for querying Data Lakes in a unified manner. Squerall-GUI produces three input files used by Squerall to execute queries:

• Config: It stores information needed to connect to a data source, e.g., host, port, user, password, cluster name, replicas number, etc.
• Mappings: A dedicate database (embedded) storing mappings between data and ontology terms.
• Query: SPARQL query to pass to Squerall for execution.

Configuration

Open conf/application.conf file and set values for the following configuration options:

• sourcesConfFile and mappingsDB point to the path of the config file and mappings database, respecitvely.

sourcesConfFile = "/path/to/config"
mappingsDB = "/path/to/mappings.db"

• pathToParquetToolsJar points to where parquet-tools JAR is stored. parquet-tools is an external tool that Squerall uses to extract schema from a Parquet files (see 2. Mappings UI below). It can be downloaded from here.

pathToParquetToolsJar="/path/to/parquet-tools-1.10.1.jar"

• play.http.secret.key stores the application secret key (needed for real production deployment, see here for explanation). The key can either be set manually (minimum eight charecters) or generated using the command: bash sbt playGenerateSecret.

play.http.secret.key="UtdjTsV32Dus<E1UDs:Xv]YE]UENJvJ7U9ei@L@MIb/`iG^obB_oBLs3z<kpotg72"
play.http.secret.key=${?APPLICATION_SECRET}

Execution

To build and run Squerall-GUI, run the following commands from the root of the project:

sbt compile
sbt runProd

Or directly sbt runProd.

Squerall-GUI can then be opened by navigating to localhost:9000/squerall.

Usage

Squerall-GUI consists of three interfaces:

1. Connection UI

It is used to generate the config file, it shows users the options they need to provide in order to connect to a data source. Those are Spark and Presto options, an example of MongoDB options in Spark can be found here, and in Presto here.

2. Mappings UI

Using the information collected by the previous GUI, data schema is extracted showed to the user. The user searches for Ontology properties and classes to map data attributes and entities. The search is powered by the LOV catalog, but users can enter their own terms.

Mappings are saved in their dedicated database, users use this interface to generate the mappings file used by Squerall to query the data.

3. Query UI

It guides users through the creation of SPARQL queries. Users provide input to widgets, and the interface creates the query for them. The interface auto-suggests Ontology terms from the mappings collected by the previous interface. This interface helps users create queries that potentially return results; e.g., if they choose terms not known in the mappings, the query will not return results.

Try it

A Dockerfile is available to have a quick look at Squerall-GUI. Navigate to the root of the repo (where Dockerfile is located) and then run:

sudo docker build -t squerall-gui . # wait till finished
sudo docker run -p 9000:9000 -it --rm squerall-gui

Once done, open your browser at localhost:9000/squerall.

To see the generated config files, you need to log in to the container by opening a bash inside it. To do so, run sudo docker ps and note the container name/id running the squerall-gui image. Then run:

sudo docker exec -it [container_ID/name] bash

Once in the bash, navigate to cd /usr/local/squerall-gui/conf, there you find config and mappings.ttl files.

Or, watch a walkthrough screencasts at: https://drive.google.com/drive/folders/10mkwMrbuxv71gtwE2etDzqANt8S9YXhr

Technology

Squerall-GUI is built using the open-source Play Framework (v2.7.0) in Scala language. It makes use of Nitrite database as a light-weight embedded document database.

Contact

For any inquiries, please contact me on: mami@cs.uni-bonn.de, or ask directly on Gitter chat.

License

This project is openly available under the terms of the Apache License v2.0 (read for more).