"Inline-level" tags are elements like emphasis, hyperlinks, etc. They wrap text within a block-level element. These elements do not cause the text to break when rendered in a paragraph format, but typically they cause the document processor to apply some kind of distinct typographical treatment to the enclosed text, by changing the font, size, or similar attributes. (The DocBook specification "does" say that it expects different typographical treatment, but it does not offer specific requirements as to what this treatment may be.) That is, a DocBook processor doesn't have to transform an codice_15 tag into "italics". A reader-based DocBook processor could increase the size of the words, or, a text-based processor could use bold instead of italics.