Sutra period existed roughly between 1000 B.C. to 200 B.C. it
is during this period Brahmins became divided into various Sakhas
/ branches. Shakhas means the school from which the students
learnt the Ved's and its interpretations. The teachings of the
Rishis are called sutras. Every Ved has its own sutras. The
sutras that contain social, moral and legal ascepts are called
dharma sutras, the sutras that deal with ceremonials are called
Srauta sutras and the sutras containing domestic rituals are
called gruhya sutras. Sutras are generally written in prose
and verse. These sutras are based on Ved's therefore they are
known as Smritis which means remembered.
Dharma Sutra of Shukla Yajur Ved is Shankkhalikita.
Rishi was the most ancient sage of all Brahmin law givers. He
was belonged to Sam Ved School. Gautam's teachings are known
as Gautam sutra / Gautam smriti.
Rishi was also the author of Dharm Sutra known as Gautam Dharm
Sutra which is the earliest Dharm Sutra containing 28 chapters
with 1000 aphorisms.