The invention includes a system for product selection, the system including: a CPU; a memory operatively connected to the CPU, the memory containing a program adapted to be executed by the CPU and the CPU and memory cooperatively adapted for presenting a user interface and expert interface to an expert system for product selection; a expert-interface code segment embodied on a computer-readable medium configured and adapted for: creating and modifying via a graphical user interface a graphically-displayed tree structure representing a plurality of product applications; associating and modifying via a graphical user interface one or more use condition with each node of the tree structure; and associating and modifying via a graphical user interface one or more suitability ratings for a plurality of applications; creating and modifying via a graphical user interface a list of products associating and modifying via a graphical user interface one or more product with each leaf node of the tree structure; associating via a graphical user interface use condition choices with each product associating via a graphical user interface suitability ratings for each product a user-interface code segment embodied on a computer-readable medium configured and adapted for selecting via a graphical-use interface a path in the tree structure, and for displaying on the same window of the graphical-use interface: the products associated with the leaf node of the selected path; the use conditions associated with each node of the selected path; and the product usability suitability indicators associated with each node of the selected path; selecting via the same window of the graphical-use interface one or more of the use conditions associated with the nodes of the selected path and for entering the user-defined relative importance of the product usability suitability indicators for the intended application of the products associated with the leaf nodes of the selected path; comparing the selected use conditions with the displayed products, where products not having such selected use conditions as attributes are filtered out of the displayed list of products; comparing the entered relative importance of the product usability suitability indicators with the product usability suitability indicators associated with the displayed products, associating a score with each displayed product indicating the correlation of the comparison, and displaying the score with the product; and printing the resulting product list, corresponding suitability scores, selected tree path, selected use conditions, and entered relative importance of product usability suitability indicators.