PDF versus TIFF: Storage Media Dependency

One of the most important factors involved with recommending a storage subsystem is the legal compliance of the documents, the weight (value) and relevance (importance) of the documents. When a Certified Document Imaging Architech (CDIA) is tasked with designing an Electronic Document Management System (EDMS), he or she will at some point be responsible for recommending the proper storage subsystem (i.e. RAID, SAN, NAS, optical jukebox, tape library, etc.) and storage media type (i.e. magnetic drives, magneto-optical, CD-R, DVD-R, etc.) to achieve compliance. However, a less obvious factor to consider for achieving compliance is how the image file format affects hardware selection.


In the document imaging world, there are two dominant file formats to consider when storing scanned paper business documents as images, the Tagged Image File Format (TIFF) and/or Portable Document Format (PDF).


The TIFF is an industry standard file format and is "platform-independent" (i.e. Windows PC, Apple/Mac, UNIX, etc.). TIFF was originally developed by Aldus and Microsoft, Inc. and the specification was owned by Aldus, which in turn merged with Adobe Systems, Inc. Consequently, Adobe Systems now holds the copyright for the TIFF specification and claims the trademark originally registered to Aldus. The TIFF image file format is very flexible and supports several color spaces (i.e. bitonal, grayscale, RGB, etc.) and compression schemes (i.e. raw uncompressed, CCITT Group 3 & 4, Unisys LZW, etc.) and is a raster image file format. Because raster images can be easily altered in an image editing program (Windows Imaging, Photoshop, MS Paint, etc.), the TIFF image format needs to be stored in a read-only format on Write Once Read Many (WORM) media (i.e. Magneto-Optical, CD-R, DVD-R, etc.) immediately after creation and validation by authorized personnel to maintain legal compliancy.  TIFF images can be stored on non-WORM storage media only if one of the two conditions is met, (a) paper originals exist (b) micrographics (microfilm, microfiche, etc.) of paper originals are maintained. TIFF images stored on magnetic media (i.e. DASD/hard drive, RAID, SAN, Network Attached Storage (NAS), DLT tape, etc.) without original paper or micrographic backups could spell legal woes if ever challenged in a court of law.


The PDF file format was developed and released by Adobe Systems in 1993 and has become the de facto standard in electronic document distribution worldwide. It was originally developed for the US federal government to store its legacy files. In fact, the US federal government is still the largest user of the PDF file format. The PDF file format uses a variable compression scheme to create small portable file sizes. An innovative feature of PDF is the ability to perform file streaming, in which a user can request a multi-page document across a network and will receive the first requested page immediately while the remaining pages download in the background. The PDF file format has several additional features including self-contained annotations, comments, security and document encryption, just to name a few. When a user makes changes to a PDF file, it will record these changes and alert others as to the validity of these changes. In essence, you cannot alter a PDF document without leaving an electronic footprint, regardless of the storage media type. Managing the storage and archival of scanned business documents with the PDF file format is a much easier process due to the fact that it can be maintained on any storage media. The PDF file format is both "platform-independent" and "storage media-independent".


In summary, a CDIA must perform a thorough Needs Assessment with the client to determine the proper storage subsystem and media type based on the data collected and the clients business requirements. For example, if a client images business documents and disposes of their paper originals but needs immediate access and the ability to share scanned documents via the internet, PDF is an excellent choice while storing on magnetic media. Keep in mind, with the TIFF file format, if no paper originals or micrographic originals exist, the scanned TIFF images are your only legal originals and must be stored on WORM storage media to maintain legal compliance. With the PDF file format, the storage media type is not an issue because the PDF file format is considered a legally binding original in a federal court of law regardless of the storage media type.


Erin Spalding, CDIA+
CDIA+ Instructor


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