Since my designs follow object-oriented design principles, my XSD schemas import multiple XSD schemas, which provide and permit reuse of many of their simpleTypes and complexTypes. The time for a successful validation of a schema that solely imports 9 other schemas and does not have any data-type or element definitions was in excess of 10 minutes. The subsequent validation took 3 minutes. 2.66 out of 4 gigabytes of memory and 50% of the CPU were used. I validated with Saxon-EE 9.4.0.3 for XSD1.1. I suspect that the problem is that Saxon validated all of the imported schemas. Since these schemas had NOT been changed after their previous validation, this was a total waste of time! Does Saxon have a tool to check the time of the previous validation against the time of the last edit? If not, it needs one. There is a potential problem when two schemas import each other. In this case, it probably pays to validate both. A quick way to ameliorate this problem is to extend the validation-well-formatted pull-down to include Validate only this schema. Since a schema tree structure is needed to perform an intelligent validation, it would be useful to make this tree available to the user and to note if any of the imported schemas were not being used. Has anyone else observed similar long validation times with another validator? Thank you. Yours truly, Bob Leif