Summer Institute on Data Curation:

Digital Preservation& Standards

Jerome McDonoughAsst. Professor, GSLIS

June 4, 2008

I love standards. There are so many of them to choose from.

Standards & Sustainability

Disclosure: Are complete specifications available? For free?

Adoption: To what extent is the standard already used?

Documentation: Is the specification clear and straightforward? Are there additional resources to assist in understanding the standard?

Standards & Sustainability

External Dependencies: To what extent does use of the standard rely on particular hardware or software? On other standards? On other non-standards?

Impact of Patents: If patents cover some or all of the standard, are licensing issues likely to complicate use of the standard?

Technological Protection Measures: Does the standard rely on technological protection measures which will inhibit your ability to preserve data?

Tip of the hat to Library of Congress Sustainability Of Digital Formats Sitehttp://www.digitalpreservation.gov/formats/sustain/sustain.shtml

Part I:How to Operate an

Archive

Open Archival Information System

Reference ModelDeveloped by the Consultative Committee For Space Data Systems

Adopted as ISO 14721:2003Available at http://public.ccsds.org/publications/archive/650x0b1.pdf

Provides definitions of components of an archive, their relationship to each other, a set of mandatory responsibilities for an archive, and both functional and data models.

OAIS Reference Model:Mandatory

Responsibilities Negotiate for an accept information from producers Obtain sufficient control of information to ensure long-

term preservation (including necessary IP permissions and authority to migrate)

Determine which communities should be the Designated Communities and should be able to understand the information provided

Ensure that the information to be preserved is independently understandable to the designated community (i.e., they can understand it without the assistance of experts who created it ).

Follow documented policies and procedures ensuring information is preserved against reasonable contingencies

Make the information available to the designated community

OAIS Functional Model

OAIS Functional Model: Ingest

OAIS Functional Model: Archival Storage

OAIS Functional Model:Data Management

OAIS Functional Model: Access

OAIS Functional Model:Preservation Planning

OAIS Functional Model: Administration

OAIS Data Model

Part II:How to Create Content

for an Archive

Archival Content

A syllogism to ponder:No digital media can be read without a hardware device designed to read the media format.

It is exceedingly rare for a hardware device intended to read a specific digital media format to be manufactured for more than 30 years, and many have had shorter lifespans.

Therefore, if your content is not device independent, it is not really archival.

Archival Content: Text

Some Issues to Consider When Examining Text StandardsTechnical aspects of character encoding

Character Repertoire (Script & Language Support)

Line Break Handling & Line OrientationIndexingFormattingOther processing

Archival Content: Text

A Standard for CharactersUnicode 5.1 - ISO/IEC 10646

Two variable length encodings (UTF-8, UTF-16) and a fixed length encoding (UTF-32). In UTF-8, byte order is not an issue. In UTF-16 and UTF-32, big-endian and little-endian encodings are supported.

Over 100K characters, supporting 75 different scripts and many additional symbols and diacritics, with room for expansion to 1,114,112 characters.

Support for a variety of line breaking mechanismsSupport for different text directionality, including algorithms specifying the appropriate handling of text of mixed directionality

Archival Content: Text

A Standard for Syntax XML (World Wide Web Consortium)

Standards for Semantics Chemical Markup Language, Chemical Industry Data Exchange

Astronomical Markup Language, Astronomical Dataset Markup Language, Astronomical Instrument Markup Language

Earth Science Markup Language, Geography Markup Language, NetCDF Markup Language, ArcGIS Markup Language

MathML Etc., etc., etc….

Archival Content: Images

Some Issues to Consider When Examining Image StandardsColor DepthColor SpaceColor ManagementImage Resolution ScalabilityCompression

Archival Content: Images

Tagged Image File Format (TIFF) 6.0 -- 1 to 64-bit color depth, supports grayscale, RGB, YCbCr, CMYK and CIELab color spaces, supports embedded ICC color profiles, raster format, supports uncompressed as well as lossless and lossy DCT-based compression

JPEG 2000 (ISO/IEC 15444) -- 1-48 bits per channel with multiple channels (including alpha & transparency), supports wide array of color spaces with sRGB and sYCC as defaults, supports ICC color profiles, raster format, supports uncompressed as well as lossless and lossy wavelet based compression

Scalable Vector Graphics 1.2 -- uses sRGB color spaces, supports ICC Color Profiles, vector format

Archival Content: Audio/Video

Some Issues to Consider when Examining Audio/Video StandardsAudio sampling rateAudio bit depthVideo frame rateVideo color space/depthCompression

Good News: Audio/Video is a bit more standardized than text/image world

Bad News: Lossless digital audio is rare; lossless digital video is almost nonexistent.

Archival Content:Audio/Video

Broadcast WAVE Audio (EBU Standard N22 - 1997)

For video, picture is less clear. Proprietary solutions dominate market. Many of these (e.g., QuickTime, WMV) do support lossless image frame and audio data. MXF, a SMPTE standard, is gaining some traction in digital library circles (and the movie industry)

Archival Content: Data

Some disciplinary de facto standards (e.g., Chemical Markup Language). Cover Pages (http://xml.coverpages.org) is a good source for information on many of the major ones.

No single standard for general use for data encoding, although many contenders

Archival Content: Data

Binary Format Description Language (BDFL) -- XML language based on the Extensible Scientific Interchange Language (XSIL) that supports documentation of binary and ASCII data

eXtensible Data Format (XDF) -- scientific data format supporting hierarchical data structures, N-dimensional arrays, scalar and vector fields, user-defined coordinate systems

Archival Content: Data

Data Format Description Language (DFDL) -- A language for describing the structure or binary and character encoded data to expose their structure, format and metadata so that machine processes can work upon them.

Data Documentation Initiative (DDI) -- An effort by the ICPSR at Univ. of Michigan to develop an XML format for documenting social science data sets. XML files can be used to produce either bibliographic descriptions of data sets or SAS/SPSS/STATA data definition statements.

Archival Content: Data

Hierarchical Data Format (HDF5) -- General purpose file format (with supporting software library) for storing scientific data, developed by NCSA. Uses two fundamental structures, groups and data sets, where a data set is an N-dimensional array of data elements with metadata.

Archival Content: Paper

ANSI/NISO Z39.48-1992, Permanence of Paper for Publications and Documents in Libraries and Archives

ISO 9706-1994, Information and documentation -- Paper for documents -- Requirements for permanence

Part III:How to Create Metadata

for an Archive

Metadata: Identifiers

Persistence is important, but…Clarity on what is being identified may be more important (or, why an OpenURL is not a call number).

Standards proliferate in this space; choice of any identifier may depend on:Social concerns (for whom am I identifying something?)

Identifier/address resolution (how do I find a copy/item using this identifier?)

Metadata: Structural

Metadata intended to identify the components of an object and their relationship to each other in order to support the object’s navigation and use

Metadata Encoding & Transmission Standard (METS)

MPEG-21 Digital Item Declaration Language

XML Formatted Data Units (XFDU)OAI-ORE

Metadata: Provenance

Metadata documenting the origins and life-cycle of a digital object

PREMIS Data Dictionary for Preservation Metadata 2.0Joint project of OCLC & RLGDefines metadata element set that “supports the viability, renderability, understandability, authenticity and integrity of digital objects in a preservation context.”

Metadata: Provenance

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

The PREMIS Data Model

Metadata: Provenance

PREMIS Object Metadata:IdentifierCategoryPreservation LevelSignificant PropertiesCharacteristics (fixity, size, format, etc.)Original NameStorageEnvironmentSignatureRelationships to other Objects, Events, Rights

Metadata: Provenance

PREMIS Event MetadataIdentifierTypeDate & TimeDetailsOutcomeRelationship to Agents and Objects

Metadata: Provenance

PREMIS Agent MetadataIdentifierNameType

Metadata: Provenance

PREMIS Rights MetadataRights StatementRights BasisCopyright InformationLicense InformationStatute InformationRights GrantedRelationship to Objects and Agents

Metadata: Administrative

Technical MetadataZ39.87 and MIXTechnical Metadata for Text (TextMD)AES-X098 Administrative Metadata for Audio Objects

SMPTE RP210.10-2007 Metadata Dictionary

Rights MetadataStandards, yes. That you want to use, no.

Metadata: Descriptive

Issues to consider:Nature of object to be describedReal purpose(s) of descriptionCommunity(ies) that will utilize description

Supporting standards of descriptive practice and controlled vocabularies

Metadata: Descriptive

Library/Archives/Museums/EducatorsMARC, MODS, Dublin CoreEADVRA Core, CDWAIEEE LOM

Data RepositoriesData Documentation InitiativeContent Standard for Digital Geospatial Metadata

Darwin CoreAccess to Biological Collection Data (ABCD)

How to Evaluate an Archive

Evaluating Archives

Trustworthy Repositories Audit & Certification (TRAC) Criteria & Checklisthttp://www.crl.edu/content.asp?l1=13&l2=58&l3=162&l4=91

Digital Repository Audit Method Based on Risk Assessment (DRAMBORA)http://www.repositoryaudit.eu/

Exercise: URLs

Imageshttp://people.lis.uiuc.edu/~jmcdonou/Bryce.tif

http://people.lis.uiuc.edu/~jmcdonou/Bryce.jp2

Exercise: URLs

METS Schema, Documentation, Namespace http://www.loc.gov/standards/mets/mets.xsd http://www.loc.gov/standards/mets/docs/mets.v1-7.html http://www.loc.gov/METS/

PREMIS Schema, Documentation, Namespace http://www.loc.gov/standards/premis/v1/PREMIS-v1-1.xsd

http://www.loc.gov/standards/premis/ http://www.loc.gov/standards/premis/v1

MIX Schema, Documentation, Namespace http://www.loc.gov/standards/mix/mix20/mix20.xsd http://www.niso.org/kst/reports/standards?step=2&gid=

None&project_key=b897b0cf3e2ee526252d9f830207b3cc9f3b6c2c

http://www.loc.gov/mix/v20