Strategic Thinking and Significant Characteristics Hamish James

Recap: Complexity datamedia + drive + computer + operating system application + display +

Basic Preservation Strategies Migration: convert the data to work with new applications Emulation: convert the data, application (and operating system) to work on new hardware Technology preservation: Keep everything running

Newer Ideas Virtual computing: create a standard ‘virtual’ runtime environment Migration on demand: convert original format directly into up-to- date format

In Theory Open Archival Information System

In Practice In practice, migration is the simplest and most common approach Limitations of migration are: –Can be difficult to ensure accurate migration –Does not capture functionality, only (possibly partial) data –May need to be repeated frequently –Might lead to ‘mutation’ over time

What to Preserve?

Significant Characteristics Very difficult to preserve everything (data, functionality and interaction) about a digital resource Documented or commonly understood significant characteristics help simplify preservation actions

Book Significant: Words, paragraphs, chapters, author, publication date, … Not Significant: Binding, print run, font, colour of paper, …

Newspaper Significant: Words, paragraphs, headlines, size of type, date, page number of article, … Not Significant: Size of page, spacing, text justification, colour of paper, …

Digital Resources There is a shared understanding of what is important in a paper-based resource Less agreement about what is important in a digital resource Complicated to decide as software and formats support many options that are not knowingly used but have default settings

Digital Examples Digital ObjectSignificant Characteristics plain text filecharacters (lines) word processor filecharacters, lines, paragraphs, fonts, styles, bookmarks? … database filevalues, fields, data types, relationships, reports? forms? … still imageresolution, colour depth, palette, metadata? … moving image clipresolution, colour depth, palette, frames per second

Question What are the significant characteristics of your digital outputs? –What are the digital objects that make up your resource? –What is the purpose of your digital resource?

Digital Resources by Type Textual Documents Still Images Moving Images Audio files Numeric dataset Database Markup Documents (XML etc.) CAD GIS Virtual reality Website Software executable

Digital Resources by Purpose Original digital recording (audio, moving image etc.) Digital surrogate of an analogue work (text, image, audio etc.) Primary research data Processed research data Learning and teaching resource Working paper, report or published paper Catalogue Computer model or simulation Software product

Summary Think about the problem in terms of content and purpose Very difficult (if not impossible) to ensure your resource stays exactly the same in the future –What can change without adverse effects? –What changes must be limited, and by how much? –How can you check changes are acceptable?