> For the complete documentation index, see [llms.txt](https://gl-docs.gitbook.io/zkpass/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gl-docs.gitbook.io/zkpass/zkpass-developers-guide/zkpass-modules/dvr/dvr-query.md).

# DVR Query

The query language is implemented by the DVR Query Engine component, which takes two inputs:

* <mark style="color:orange;">**User Data**</mark>\
  This is the JSON data that is issued by the Data Issuer and is being inquired by the Proof Verifier to see if the data meets specific requirements or conditions. The data can follow any schema or structure as DVR does not set any specific format requirement on the user data.
* <mark style="color:orange;">**DVR Query**</mark>\
  The query is a JSON-based script that sets the requirements or conditions for the user data. The query is expressed as a DVR scripting language and is included in the "query" field of the Data Verification Request (DVR) object.\
  An example of the query would be “user must be either married or over 21 years of age”.\
  The query is executed by the DVR Query Engine to produce the ZK Proof and the result of the query.

The goal of defining its own query language is to let the Proof Validator client be able to perform queries on the data using an expressive, flexible, intuitive, easy-to-use, and performant scripting language.&#x20;