Accurate recording of what is being uncovered during excavation is an absolute obligation upon all archaeologists, whatever their background and experience. Once an excavation has started, every piece of information retrieved from the site must be related to the layers, finds and structures around it, so that the complex relationships which contribute to the interpretation of the site can be recorded. An example might be a Roman pottery kiln, where the position and quantity of the pottery itself, the kiln structure and waste material from the manufacturing process are together essential to our understanding of the site - just an individual piece of pottery detached from this other information loses almost all its significance.
Each layer, structure or deposit uncovered during an excavation is called a ‘context’ and given a unique context number. These can run into many thousands, and even more on very large and complex sites. As the site is excavated, each context is described and related to artefact finds and surrounding contexts. Written records, on paper or computer, record this basic site information. Scale drawings (called ‘plans’) and photography record each context visually. Lists of contexts, finds, soil samples, plans, photographs, human and animal bones need to be kept up-to-date and correct because these will be used later to re-trace the steps taken during the excavation. When the excavation itself is finished but the resulting mass of information still needs to be sorted, processed and written-up, this is called the ‘post-excavation’ phase of work, often abbreviated to ‘post-ex’.
When excavation and post-excavation phases are complete, future researchers should be able to re-investigate the archaeology by searching the site records - asking questions that could have been asked of the original archaeology, such as, for example, the depth of stratigraphy, the size of buildings or the quantity and content of storage pits. The information which results from excavations is only of permanent value if it is made available to other people by publication, and by the site records being deposited in publicly-available archives.