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Subject: DOCBOOK: Re: imagedata: entityref vs fileref
/ Patrick Eisenacher <eisenacher@fillmore-labs.com> was heard to say: | I'm new to the list and I have a question regarding the use of the | entityref and fileref attributes when including an image via the | imagedata element. When do I use which attribute? Is it merely personal | preference? What are the benefits? What are the drawbacks? What is the | preferred way? It is, to a large extent, personal preference. The use of entities provides a degree of indirection that is sometimes useful. It was more common, perhaps, in the pre-XML (and pre-web) days before URIs were a widespread concept. In order to use entityref, you must setup a more complex document structure: <!DOCTYPE article PUBLIC "..." "..." [ <!ENTITY graphic PUBLIC "..." "..." NDATA PNG> ]> <article> ... <imagedata entityref="graphic"/> When the document is processed, the PUBLIC and SYSTEM identifiers are used to resolve the actual location of the 'graphic'. This means that a catalog or other resolver mechanism can make dynamic selections. It's also possible to put the entity declarations in an external file and switch between them wholesale. For DocBook: TDG, there are several hundred 'unicode character' graphics. For the HTML version of the book, these are all PNGs; for the print version, they're all EPSes. I switch between the two by selecting different sets of entities. | The processing expectations say: |> There are two ways to provide content for ImageData: EntityRef or FileRef. It is best to use only one of these methods, however, if multiple sources are provided, EntityRef will be used in favor of FileRef. | | How do I have to understand 'if multiple sources are provided' - if I | specify a fileref and an entityref attribute for the same imagedata | element? Yes. Be seeing you, norm -- Norman Walsh <ndw@nwalsh.com> | Extinction, n. The raw material http://www.oasis-open.org/docbook/ | out of which theology created the Chair, DocBook Technical Committee | future state.--Ambrose Bierce
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