A site or ‘Harris’ matrix is a diagram which depicts layers, structures and features, with their relationships and sequence, in an abstracted and clarified form. A form of flow-chart going from latest (top) to earliest (bottom), a matrix has lines linking boxes, inside which are written the context numbers of the layers which they represent. These help in the process of recording, clarifying and understanding the build-up of deposits which an excavation encounters. 

It is called a ‘Harris’ or sometimes a ‘Harris-Winchester’ matrix because it was invented by the archaeologist Edward Harris, who at the time was working on excavations in Winchester, Hampshire. The Winchester excavations, directed by Martin Biddle in the 1960’s and early 1970’s, were some of the first large-scale urban investigations in Britain. The complexity of the archaeological layers and structures uncovered there were a challenge to existing recording practice, and required new approaches. The Harris matrix has now become a useful interpretative tool which is used for many sites at both the excavation and post-excavation stages.