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Writing a Data Query for an LOI

A data query is used to obtain the data required to answer the question template of the LOI.


The data query will be executed on an external data repository that has a data adapter that integrates it with DISK. The current implementation of DISK supports queries for data using SPARQL as the query language.
Developers can extend DISK to integrate new data sources and create new data adapters.

Writing a Data Query in SPARQL

The starting point of the query are the Question Variables specified in the Question Template.

You can write the query by clicking on the Query text area.


The next example shows a data query for neuroscience data. The query follows several steps to obtain the data:

  1. Using the Question Variable ?Genotype to find the ?Cohort
  2. Using ?Cohort to find the ?dataset
  3. Using ?dataset to find the ?schema
  4. Using ?schema to find ?url

The query also includes at the end the Workflow Variable: Url that is passed as an input to the workflow of the LOI, as we describe next.

Data Query

Specifying Workflows and Meta-Workflows

To specify the workflow of the LOI, you need to select the button Add Workflow and select the workflow from the list of workflows.


Next steps

In the next section, you will learn how to select workflows and select the workflow inputs.