Expert System

The expert system approach is essentially looking for patterns in complex dynamic phenomena that have proved to be beyond standard quantification techniques. For example 'ship decoration' cannot be quantified. The outcome of the expert system is a probability statement concerning the tool type or function that is most consistent with the observations. The interpretations are made according to the balance of indications given by the expert system rules and based on the observation of all features.

Expert systems are not intended to replace human experts. For example, the recognition of retouch on stone tools as opposed to edge damage (from spontaneous retouch, trampling, post depositional movement, etc.), is dependent on the analyst's experience and in particular on experimentation, involving not only observation of experimental and archaeological tools , but also an appreciation of the mechanics of making and using stone tools.

The use of expert systems has a number of advantages over other techniques. Increased consistency and standardisation. The development of an expert system means that the observational techniques have to be systematised and the rules provide a base from which results can be assessed.

Different analysts using the same program will obtain the same results. This has been repeatedly confirmed during instruction in use-wear analysis when several students have independently analysed the same experimental tools and all interpreted the correct function of the tool using FAST. Often students enter different observations, due to inexperience, but the flexibility of the program (in particular the 'fuzzy logic' aspects) allows for this so that some variations in observations can be accommodated.

The use of rule based expert systems is a practical approach to lithic studies that bridges the gap between processual and post processual archaeology. The key here is rules; not laws which are inviolate, but rules that can be changed and indeed are always changing in a reflexive relationship allowing the expert system to accommodate new information.
The rules of the expert system are subjective, but they are explicit in that they are written down and incorporated into the computer program. The observations are defined and the rules are explicit therefore anyone can produce the same results, so that though the system is subjective it is consistent when different subjectivities (i.e. different individuals) use it. The acceptance of the assumptions on which the program is based leads to consistency, and direct comparability between results produced by different people; this fulfills the basic requirements of objective data within the consensus reality of mutual users of the program. Therefore expert systems can extract objective-like data, but the complexity of the dynamic process is retained and the data is produced in the form of probabilities that can be compared as if they are objective data within a defined consensus reality.

Expert systems are so called because they are designed to model the behaviour of a human expert. So they are modeling human behaviour, in fact an individuals behaviour. By extension expert systems can be used to model the more complex behaviour of societies. A series of programs that input the results of each individual program into another program further up the hierarchy is being developed. Not only must the interpretations be consistent with use-wear analysis and lithic programs, but non-lithic material such as the faunal assemblage, environmental evidence and spatial information from the site and any chronological evidence.
Alternative interpretations can be modeled with expert systems so rather than postulating a theory and then testing it, a number of alternatives can be tested and matched against the data simultaneously.

(source: hf.uio.no/iakh/forskning/sarc/iakh/lithic)