Constraint-based representation scheme

Constraint-based Representation Scheme. The primary feature of the chemists ability to specify QC criteria based on the QA/QC Objective and other inputs is that the QC criteria are specified as a set of general constraints and limits which the data must adhere to. For example, for a PCB site with a QA/QC Objective level of QA2, the experts could specify constraints for the data such as "the matrix spike duplicate recoveries should be between 801 to 120Z", and that "the PCB detection level must be at least 1.5 ppm." Therefore, a constraint-based representation presents a natural mechanism to emulate the thought process of the chemists in developing QC criteria. 

Knowledge Representation for IQAP. Three knowledge representation schemes, i.e., relational, rule-based and frame-based, and constraint-based, were examined for developing IQAP s knowledge base. For a general description of some knowledge representation schemes (4). 

It is also possible to use internal coordinate representations to treat constraints, i.e. parameterization schemes, which are typically based on partitioning the coordinates of the system into a set of independent variables and a complementary collection of dependent variables (which are expressed in terms of the first set). These approaches result in systems of slightly smaller dimension, but typically greater complexity. Moreover, the parameterization is typically local which leads to additional implementation issues. For some details on such schemes and discussion of their use in molecular simulation, the reader is referred to [20, 190, 255]. 

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