Relative dating with stratigraphy is based on the principle of
Contexts are single events or actions that leave discrete, detectable traces in the archaeological sequence or stratigraphy.
They can be deposits (such as the back-fill of a ditch), structures (such as walls), or "zero thickness surfaciques", better known as "cuts".
When archaeological finds are below the surface of the ground (as is most commonly the case), the identification of the context of each find is vital in enabling the archaeologist to draw conclusions about the site and about the nature and date of its occupation.
There are two different principles of stratigraphy.
The first principle is the principle of the original horizontality. Study of layered sedimentary rocks, especially their formation and relationships.
One issue in using stratigraphic relationships is that the date of artifacts in a context does not represent the date of the context, but just the earliest date the context could be.
If one looks at the sequence in fig A, one may find that the cut for the construction of wall 2, context 5, has cut through layers 9 and 10, and in doing so has introduced the possibility that artifacts from layers 9 and 10 may be redeposited higher up the sequence in the context representing the backfill of the construction cut, context 3.