[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Structured from/within unstructured documents
On Sat, 15 Dec 2007 18:04:41 +0000, Stephen Green wrote > What methods are there, these days, for extracting structured data from > unstructured documents (such as PDF)? PDF documents are typically not really "unstructured". There is the metadata (Title, author, creator etc.) and the pages as graphically intended to be viewed. Unless the contents are purely image data (scanned in) one can just render it to text (same applies to MS Word, Postscript and a host of other formats). The text has typically some intended structure. The rest is the old art of auto-tagging. In indexing PDF documents we routinely extract basic structure such as sentence, paragraph and page-- in PDF we don't bother with line. This is generic enough that we found it can nearly always be applied. For the intent of search and retrieval we've indexed many millions of millions of PDF documents over the years. The metadata we've found typically of very limited use (almost always not correctly maintained). Sentence, paragraph and page identification is, by contrast, given the conventions of writing. very reliable. For more complicated and detailed structure its less generic and one needs to define some regular expression models and rules to define what makes for whatever structural element one is looking for. Typically, however, for PDF in the applications were a finer structure is needed there are other, alternative, formats of the information available. One can, of course, using other methods even break things down into linguistic and grammatical elements as well as determine things like place names, person names, inter-relationships etc.: the whole bag of textual analysis. -- Edward C. Zimmermann, Basis Systeme netzwerk, Munich Office Leo (R&D): Leopoldstrasse 53-55, D-80802 Munich, http://www.nonmonotonic.net
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