The Hydra user reference is divided into categories where each category corresponds to one of the components a Hydra job. Each category has is a summary page that provides a description of the category and a list of each item in the category. The list of items includes a brief description for each item.

The approximate status of the documentation writing for each category is:

Category Description
 
Hydra Jobs top-level specification of the Hydra jobs
Input Sources input to a job
Bundle Filters transformations that accept a bundle as input
Value Filters transformation that accept a value as input
Output Sinks output from a job
Path Elements describe the nodes in tree output
Data Attachments additional information that is attached to tree nodes
Query Operations query operations that are performed on tree output

Most Hydra jobs are specified using one of the forms listed in the "Hydra Jobs" category. This would be a good place to start if you have just started reading this reference guide. The most common types of Hydra jobs, split jobs and map jobs, are both specified using the 'type : "map"' specification.

Each documentation page should include a summary of the item, one or more examples illustrating how to use that item in a job specification, and a description for each field of the item. If you have any questions, comments, additions, or suggestions for the documentation please submit it on IRC on #hydra at freenode.net or github.