do you consider this as a demotion?

the employer had made their employees do works that based on their new standards doesn't required and/or irrelevant to the educational proficiencies these employees were once required for them to have during their application?

The tasks however are included in the job description but they change the standard so that the whole jod description is now irrelevant to the educational proficiencies this positions once required.

was there a decrease in salary?

there are no percievable reduction in salary,and position (i assume this is the same as job title) because they keep the job title intact (even if it is very much treated obsolete), and create a new position to replace it. I don't know how do the law define rank ( i think its a military term).

the only thing that is somewhat clear is that the employees concern are obliged to do tasks that based on the employers new standards doesn't correspond any more to the educational proficiencies of the employee which they once required. Therefore, technically, they are not qualified anymore to do the job (based on the new standard).

Also the employers is also planning to reduce these employees work load to about 10%-20% of their current assigned tasks. These 10%-20% tasks that are very much arbitrary and are very much prone for obsolesence and redundancy because of technology, design, and routine advancement.

how about you clarify what the previous and current tasks are.

otherwise, these all look well within management prerogative.