Strategic Thinking and Significant

Characteristics

Hamish James

Recap: Complexity

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data media

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drive

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computer

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operatingsystem

application

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display

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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?

interaction

softwaredata

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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 ExamplesDigital Object Significant Characteristics

plain text file characters (lines)

word processor file

characters, lines, paragraphs, fonts, styles, bookmarks? …

database file values, fields, data types, relationships, reports? forms? …

still image resolution, colour depth, palette, metadata? …

moving image clip

resolution, 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?