1	Long Term Data Storage: Are We Getting Closer to a Solution A.Stander, S. Rossouw & N. van der Merwe
2	Introduction Problems Storage media unstable Equipment rapidly outdated Software versions incompatible
3	Archival Format Possible solution is to strip away machine and software dependence and to recopy it regularly to newer media Convert to common character format such as ASCII or Unicode Unicode supports all characters across all platforms, languages and programs Standards needed for data that is only available online
4	Problems Copyright when recopying Software needed to make digital documents accessible often outdated or cannot run on later versions of the operating system Later hardware often incompatible
5	SGML & XML Standard Generalised Markup Language (SGML) – standard for representing texts in electronic format Extensible Markup Language (XML) – cut down version for ease of use Can be used to store and transfer any kind of structured data between different computer systems
6	SGML (cont..) Descriptive markup system that allows different processing instructions to be associated with the same part of the file eg. To extract data or to format it A special file, the Document Type Definition (DTD) defines the contents of the file and allows for it to be checked by a special program (parser)
7	SGML & XML (cont…) Data Independence is facilitated by SGML & XML by the provision of a mechanism that allows the replacement of a particular string by another so that different computer systems can understand each other’s character sets
8	Magnetic Media Tends to lose magnetism and must be regularly rewritten Substrate also deteriorates Needs proper storage and operating environments
9	Optical Media CD-ROM (Compact Disc - Read Only Memory) CD-R (Compact Disc -Recordable) DVD-ROM (Digital Versatile Disc - Read Only Memory)
10	Optical Media Use laser to read data stored as series of pits in metallic layer CD-R uses dye layer that is changed by laser light (can be affected by strong light) Long lifetime attractive
11	Media Life D3 Magnetic tape: 1 – 50 years DLT magnetic tape cartridge: 1 – 75 years CD/DVD: 2 – 75 years CD-ROM: 3 months – 30 years
12	Smaller Amounts of data Store as XML on CD-ROM or CD-R in ISO 9660 format Regularly recopy Use suitable storage facilities Create policies to make data available to other users
13	Management Standards needed for data that depends on software eg. To take snapshots for archival Standards needed for online data Proper migration policies needed Legislative issues must be addressed
14	Conclusion Software & Hardware independent data and optical media can solve many of the current problems Standards are needed for transient data and proper migration policies must be developed