These are rules to design a catalog. A catalog presupposes human intellectual effort, not raw computer indexing of an undifferentiated mass of keywords. Human intellectual effort is expensive, so it should be used as efficiently as possible to identify the entities of most interest to the users of collections represented in catalogs.
The bibliographic universe is complex. Catalogs should be designed to reduce this complexity for its users. Thus these rules are intended to support the labelling of bibliographic data by humans such that computers can use the labeled data to build complex indexes and displays that will appear simple to the users of the catalog. Like RDA, these rules could be used as a simple list of raw data elements that could be implemented and displayed many different ways in many different contexts. However, unlike RDA, these rules do not push most of what was formerly considered to be cataloging out of the rules and into implementation decisions and display decisions that are independent of the data elements. In addition to defining raw data elements, these rules include recommended implementation decisions and recommended display decisions, so as to try to ensure the greatest possible functionality and user service in the resultant catalog(s).
The approach recommended in these rules (to start with the work rather than the item) has the potential to allow us to create a complexly organized and extendable description for each work that can be exposed to commercial search engines such as Google. A Google searcher interested in that work can start from the work and end up with a particular manifestation of a particular expression of that work that is available at the searcher's local library, on the shelves, via interlibrary loan, or via licensed electronic delivery.