Grange implements a modern subset of the range query language. It is an expressive grammar for selecting information out of arbitrary, self-referential metadata. It was developed for querying information about hosts across datacenters. A range query operates on a state containing clusters. Range also allows for a default cluster (traditionally named GROUPS), that can be accessed with some shortcut syntax, documented below. Values can also be range expressions, so that clusters can be defined in terms of each other ("self-referential"). For an example usage of this library, see https://github.com/square/grange-server Syntax All of the above can be combined to form highly expressive queries. A number of libcrange features have been deliberately omitted from grange, either becase they are archaic features of the language, or they are mis-aligned with the goals of this library.