The first two paragraphs are redundant to some extend:
"All Attribute Names (Data Names) are listed alphabetically in Clause 6. The data in the Logical Nodes Classes are grouped into various categories (as described below) for the convenience of the reader. This grouping may result in some overlapping.
All Attribute Names (Data Names) are listed alphabetically in Clause 6. Despite some overlapping, the data in the Logical Nodes Classes are grouped for the convenience of the reader into some of the following categories."