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Document Lifetime

David G. Lister, President
Digital Daemons, Inc.

Time Factor

One of the crucial factors to consider when creating a document is the lifetime of the document. This is especially important when creating digital documents.

Consider the following scenario. You decide that you need to create a last will and testiment. You choose to do this using a popular word processing package that came with your computer. Imagine how interesting you could make the presentation. You could add audio clips of yourself reading the document to give it greater authenticity. A video clip could add even more interest. Link annotation can be added to aid the reader in understanding your final wishes.

Stop. Wait. Think.

Let's assume first that you are in your 40's. Given the current life span statistics that means that the document that you create may have to remain readable for 40 years.

  • Software - do you really think that the software the you are using to create and read the document will be supported let alone even exist in 40 years? I sincerely doubt it. We have trouble enough creating versions of software that can understand data produced two versions ago (about 3 to four years ago).

  • Hardware - let's say that you stash multiple copies of the software that you use in secure locations. Do you really think that hardware will exist in 40 years that will execute that software? Again, I sincerely doubt it. The Macintosh just celebrated its 20th birthday and I believe that you will be very hard pressed to find a Macintosh computer that can execute code written 20 years ago. When IBM produced its personal computer it used a 16 bit microprocessor. I dare say that you won't be able to find a personal computer now that will execute your 16 bit application.

  • Encodings and standards - technology is moving incredibly quickly and the standards that drive development are changing to meet the immediate needs of developers and their customers. Take for instance the LP records that have probably been gathering dust on your shelf will be suitable for a place in a museum in another 20 years. Similarly, in possibly 10 years time that video clip that you included with your document may be unplayable simply because the encoding technique will have been long since obselete. By the time your family needs to see your video recording of your will standard NTSC, PAL, and MPEG-4 will have gone the way of LP records and the often maligned "Eight Track" tape.

  • Operating Systems - operating systems are evolutionary beasts that add and remove features based upon market needs. I really doubt that I could even run the tax software that I purchased 7 years ago on my current system due to changes to the operating system software. Since then five major revisions to the operating system software have been released. That doesn't even count the service packs that seem to come with increasing frequency.

Consider the lifetime of the document that you are producing when you choose a medium of communication.

Lifetime Groups

Instead of listing types of documents by type lets categorize them by their ability to hold up over time.

Minutes to Months

Most if not all digital document formats will satisfy these short term needs. The software will be available for the foreseeable future, the hardware platform will be almost certainly be accessible, and the operating system will be still be running and supported. The greatest concern to digital document publishers for this lifespan will be who their target audience is and what capabilities their readers have. PDF and HTML will fill the document lifetime needs very nicely. Microsoft Word documents will fill the lifetime needs although reader capabilities must be considered carefully. XHTML (XML) is nice from a development point of view but the audience is somewhat limited due to browser availablity and support. ASCII or Unicode encoded documents are almost always a safe bet for content although they lack the features in the other document formats.

Months to Years

The projection here is relatively clear and the document formats mentioned above are almost certain to fill the needs in much the same way that they did in the shorter term. Just pay particular attention to the intended audience and what formats they are able to accept.

Years to Decades

The picture begins to turn darker and a little fuzzier during this lifetime. The longer the document lifetime the darker and less optimistic it gets. It is possible that ASCII or Unicode encodings will be still around and we can still easily understand these text only documents.

Never Ending

After several decades we can almost say with 100% assurity that things will have changed. The file formats, image encoding schemes, font software, operating systems, and hardware platforms that we are all too familiar with will be nothing but a distant memory (or nightmare depending upon your experiences). I would be willing to bet that the HTML file that your browser is now displaying cannot be displayed as it is now in 2 decades simply because HTML will be standard lost on the scrap heap. Yes you may be able to read this document as a text file but the true document that you are viewing now will not be viewable as intended simply because it is outdated. If that is the case then what do you do when you want to preserve a document for lets say four decades? As of now we probably have only a limited number of choices: paper or ASCII/Unicode encoded text files.

Yeah, but what about PDF?

PDF is a good standard for exchanging high fidelity, human readable documents. It is a publicly available standard published by Adobe that has withstood the test of over ten years of time. But remember, PDF is an evolving standard too. There's no telling if PDF and its associated Adobe Acrobat group of products will support all the peripheral standards such as JavaScript, audio clips, video clips, and font software embedding in the future.

The folks at Adobe work hard to maintain backward compatability. I know, I used to call the Acrobat Development group home. But there is nothing that says that Acrobat has to support all the underlying standards that make this product work.

Then there is the software life cycle. All software products are born to fit a market need (otherwise there would be no reason to invest in it or publish it in the first place), achieves a place in the market, grows to fit the needs, matures, and then dies. Right now you might think that since PDF is reliable and pervasive that it is a safe bet. But what if you intend for the document to be read in 40 years? Is PDF, Acrobat, and the array of technologies that makes the product so attractive going to be around in 40 years? Let's think about it.

The PDF was derived from PostScript technology that was developed in the 1980s. Although PostScript is still around it is a shadow of its former self because it filled a market need and matured to the point where it is considered a legacy product. A market lifetime of 20 plus years is actually pretty good these days and is nothing to be ashamed about. PDF may suffer a similar fate when it too reaches turns 20.

For documents whose lifetime is less than a decade PDF may very will satisfy your needs. Documents whose lifetime is greater than a decade, I'd stick to the type written page on paper for the time being.

Back when Acrobat was first being introduced some Adobe folks who had not caught the Acrobat religion used to say "PDF stands for Paper Does Fine."


Document lifetime is important to consider especially when longevity is of primary concern. For documents whose lifetime is less than a couple of years its more important to match the technology to that which is acceptable by the readers. For longer lifetimes you need to choose your format and medium whether it be CDROM or DVD very carefully.

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