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A different method which should be avoided is to output parts of the first element,switch to parts of the next element, return to the first, etc. In this method the structuretree is created in multiple traversals, where each traversal generates only parts of an element.Importing Pages with PDI. Pages from Tagged PDF documents or other PDF documentscontaining structure information cannot be imported in Tagged PDF mode sincethe imported document structure would interfere with the generated structure.Pages from unstructured documents can be imported, however. Note that they willbe treated »as is« by Acrobat’s accessibility features unless they are tagged with appropriateActualText.Artifacts. Graphic or text objects which are not part of the author’s original contentare called artifacts. Artifacts should be identified as such using the Artifact pseudo tag,and classified according to one of the following categories:> Pagination: features such as running heads and page numbers> Layout: typographic or design elements such as rules and table shadings> Page: production aids, such as trim marks and color bars.Although artifact identification is not strictly required, it is strongly recommended toaid text reflow and accessibility.Inline items. PDF defines block-level structure elements (BLSE) and inline-level structureelements (ILSE) (see the PDFlib Reference for a precise definition). BLSEs may containother BLSEs or actual content, while ILSEs always directly contain content. In addition,PDFlib makes the following distinction:Table 9.19 Regular and inline itemsaffected itemsregular itemsall grouping elements andBLSEsinline itemsall ILSEs and non-structuraltags (pseudo tags)regular/inline status can be changed no only for ASpan itemspart of the document’s structure tree yes nocan cross page boundaries yes nocan be interrupted by other items yes nocan be suspended and activated yes nocan be nested to an arbitrary depth yes only with other inline itemsThe regular vs. inline decision for ASpan items is under client control via the inline optionof PDF_begin_item( ). Forcing an accessibility span to be regular (inline=false) is recommended,for example, when a paragraph which is split across several pages containsmultiple languages. Alternatively, the item could be closed, and a new item started onthe next page. Inline items must be closed on the page where they have been opened.Recommended operations. Table 9.20 lists all operations which are optional, but recommendedwhen generating Tagged PDF output. These features are not strictly re-9.6 Tagged PDF 217