Natalia Wehler HS 'Digital Libraries' Standards in Digital Preservation Summary of Delos Summer...

Natalia WehlerHS 'Digital Libraries'

Standards in Digital PreservationSummary of Delos Summer School 2005see last pages for details on lecturers

Summary of Presentations of DELOS Summer School 2005

'Unpacking The OAIS Model' by David Giaretta'Categories, Uses and Challenges of Metadata and Process Documentation' by Michael Day'Workflow and Workflow Modelling' by Stephan Heuscher'Role of Registries and Representation Information' by David Giaretta



OAIS - Denotation

Open Archive Information System where

open = model standard developed using a public process and are publicly available

information = knowledge that can be exchanged, independent of form (representation)

archival information system = men and machines responsible for the acquisition, preservation and dissemination of information



The OAIS Model - History

The Consultative Committee for Space Data developed several discipline-independend standards

basis for TC20 (aircraft and space vehicles) and SC13 (data and information transfer)

general problem: information leakage through time

decided that SC13 should become archival standard



The OAIS Model - Background I

How to achieve such an archival standard? development of framework for digital archive

standards development of 'Reference Model' ensure participation (across disciplines, apart

from space communities) focus on digital formats (but keep traditional

archiving in mind)



General Definition: Archive

a structured collection of documents, certificates, files, records

orientation: long term preservation access for public

not focused on the needs of the users (in contrast to a library)

a library (institution) sometimes fulfills the functions of an archive



General Definition: Reference Model

a referece model is the basis for the development of special models

and the construction of special applications

the comparison between models which describe the same issues

a reference model represents the ideal abstract key concepts



General Definition: Framework

a framework defines the architecture of an application or a process

a framework defines the structures and the control flow

it functions as a model it helps to understand the relationship among

the entities of a system an important goal of a framework is to

create/use reusable patterns/modules



The OAIS Model - Background II

How to develop a standard? investigation of other standards definition of archiving of data break archiving into functional areas e.g.

ingest, storage, access define interface between functional areas use formal specification tools like UML, (data

classes) data flow diagrams (interfaces) etc.



General Definition: Ingest

the acquisition of digital objects for a repository

has to identify and record the appropriate semantic and syntactic properties of the object



General Definition: UML

Unified Modeling Language a standardised language to describe and

specify structures of systems not only used in software engineering, but also

to model business processes



The OAIS Model - Background IV

How is the status of the standard? widely accepted not only by digital libraries,

archives but also commercial organisations ISO 14721 and final CCSDS available



The OAIS Model -Environment

How does the model view of the OAIS environment look like?

producers provide information to be preserved

managers set OAIS policy as one concept in a broader policy domain (????)

consumers find and acquire digital information



The OAIS Model -Responsibilities

Which responsibilities does the OAIS have? negotiate for appropriate information of producers control information conscerning long term preservation ensure that the information is independently

understandable follow documented policies and procedures determine the addressee of the information make the information available



The OAIS Model-Information Terminology

information represented by data if the data object is interpreted with the help of

representation information, the information object is accessible

an information package is a conceptual unit consisting of content information and preservation description information (PDI)

types of information: rendered non-rendered others



The OAIS Model - Information Object (UML)



The OAIS Model - Representation Information (UML)



The OAIS Model - Information Types (UML)



The OAIS Model - Content Information

(primary) object of preservation needs to be negotiated between producer and

OAIS The data object in the content information can

be digital physical



The OAIS Model - Descriptive Information

contain the data which allow access to a document

can be used by the consumer e.g. to analyse or retrieve information



The OAIS Model -Packaging Information

relates the components of the package into identifiable entity of media data

e.g. tape marks, file names



The OAIS Model -Archival Information Package



The OAIS Model - Preservation Description Information

Provenance Information description of Content information source e.g.

pointers to the original, pointers to earlier versions Context Information

description of relations outside the Information Package e.g. pointers to documents from the original environment of the publication

Reference Information unique identifier e.g. bibliographic identifier

Fixity Information protection of alteration e.g. by checksum, digital

signature



The OAIS Model - Types of Information Packages

Submission Information Packages (SIP)information submitted by producer (based on negotiations between producer and OAIS)

Archival Information Package (AIP)used for preservation

Dissemination Information Package (DIP)distribution of information of one or more AIPs to the consumer using the OAIS



The OAIS Model - Functional View I

Principles: Stress on major functional areas important

to digital archiving Use of functional decomposition, but not too

detailed Identification of common services



The OAIS Model - Functional View II



The OAIS Model - Functional Entities

Ingest accepts SIPs prepares content for storage

Archival Storage provides services and functions for storage

Data Management provides services and functions maintaining descriptive

information and internal archive administration data Administration

manages the overall operation of the archive Preservation Planning

monitors environment of the OAIS provides recommendations

Access allows the consumers to access the information content of the

OAIS as a product



The OAIS Model - Digital Migration

Migration of digital information within the OAIS in order to preserve it

full information content replacement of old information

implemetation motivated by:

media decay cost effectiveness new customer requirements



The OAIS Model - Types of Digital Migration

Refreshment no bit changes

Replication no change of packaging or content information

bits Repackaging

some bits change in packaging information Transformation

reversible: bit changes can be reversed by an algorithm

irreversible



The OAIS Model - Problems of Access Presevation

cost effective use of APIs only possible if not too complicated applicable on many different AIUs (Archive Information

Unit) extensive testing necessary when porting API to a new

environment preservation through emulation of executables problematic



The OAIS Model - Archive Interoperability

need for interoperability among the different archives consumers need common aids, common DIP, common

package descriptor for access producers need common SIP, one single repository managers need cost reduction by sharing resources



The OAIS Model -Categories Archive Interoperability

independent: no knowledge from one archive to another

cooperating common submission and dissemination standards no common access

federated common access provided

shared resources resources shared but not externally visible (e.g. shared

storage)



The OAIS Model-Possible Architecture



Metadata - Definitions

Data about data Structured information to describe, explain,

locate ... information objects Definition by function

Descriptive metadata Structural metadata Administrative metadata

understandable by men and machines many different standards



Preservation Metadata - Definitions

Types of data that allow the re-creation and interpretation of structure and content of digital data over time (Ludäsher, Marciano, Moore, 2001)

The information used by an repository to support the digital preservation process (PREMIS working group, 2005)

All digital preservation strategies depend on the creation of appropriate metadata

Preserving the right metadata is the key to preservation (Duff, Hofmann, Troemel, 2003)



Preservation Metadata - Roles

reference to each digital object provides structural, descriptive, administrative

... information understanding the history of data (how it was

cleaned, what parameters were used) handling of huge amount of data

(searchability)



PREMIS WG - About

Preservation Metadata Implementation Strategies sponsored by OCLC (Online Computer Library Center)

and RLG (Research Libraries Group) since 2003 international WG main objectives:

a basic set of preservation metadata ("Data Dictionary")

strategies for encoding, packaging, storing, exchanging metadata

output: Implementation Survey Report (2004) PREMIS Data Dictionary (2005)



PREMIS WG - Observations

little experience of digital preservation: will metadata be adequate

the OAIS model was the basis for many repositories METS was the most common scheme for non descriptive

metadata metadata is stored together with data objects (self-

documenting) and in data bases

Trends keep originals to limit the risk use of multiple preservation strategies



PREMIS WG - Data Dictionary

based on OAIS framework a set of implementable semantic units defines metadata that maintains iability, renderability,

understandability, authenticity and identity in a preservation context

not focused on descriptive metadata metadata set for the needs of repositories automatic capture of metadata the Data Dictionary implementation is independent

(does not determine how s.th. is stored) everything is based on a simple data model



PREMIS WG - Data Model



PREMIS WG - Data Model - Definitions I

Entities Digital Object Interlectual Entity (considered to be covered by existing

standards) Event Agent Rights

Relationships statements of association between instances of entities

structural relationships derivation relationships dependency relationships

Semantic Units properties of one entity have values



PREMIS WG - Data Model - Definitions II

Digital Objects discrete unit of information

files = named and ordered sequence of bytes known by an operating system

bitstreams = a set of bits embedded within a file representation = the set of files needed for the

rendering of an Interlectual Entity Interlectual Entity

a coherent set of content that can be viewd as a single unit Event

an action involving at least one object or agent of the repository

objects can be connected to several actions



PREMIS WG - Limits

no focus on descriptive metadata no definition of the characteristics of an agent no consideration of rights, which are not directly associated

with preservation actions (e.g. access) no definition of all technical metadata no documentation of media or hardware no consideration of the business rules of a repository



PREMIS WG - Metadata Capture

capture metadata which already exists develop tools for automatic capture of metadata create event metadata at different points of the object life

cycle (creation, ingest, migration



PREMIS WG - Interoperability

important to support reuse of existing metadata to exchange digital objects centralised repositories specialised on file format information

and metadata schemas



Workflow - Definition

a specific representation of a process represents activities, applications and participants (humans or

machines) represents the structure of tasks, who performs a task, the

synchronisation of tasks controlled by a workflow management system can be graphically depict by workflow diagrams



Workflow - What for?

Traceability of processes, documentation of handling quality control tool for automated processes Knowledge sharing, important for

centralised implementation iterative development



Workflow and Preservation

workflows mainly for arrangement purpose implicit knowledge local differences no standards very adaptive only a small number of archives: no out of the box solutions



Workflow - Advantages/Disadvantages

Disadvantages costs complexity more surveillance too many tools and standards

Advantages documentation automation more control sharing knowledge connecting applications



Workflow - Lifecycle

Planning requirements analyses defining goals

Implementation design workflow on basis of requirement analyses evaluate tools

Enactment Evaluation Planning... (based on evaluation results)



Workflow - Routing

Routing: what to do next? manifestation of control flow definition of sequence routing needs to be defined in dependeny of the outcome of

an action



Workflow - Activities

clearly identifiable units of work always completed Hierarchy (there may be subworkflows)



Workflow - Data

activity data input and output data files, databases

routing data outcome of routing evaluated for branching



Workflow - Design

define requirements, goals textual decription of wat should happen abstraction visualisation and formalisation



Workflow - Symbols



Workflow - Example

missing: error handling data flow details



Workflow - Example

Swim lane



Workflow - Digital Preservation Specials

Formal Semantics textual definitions change meaning in time

Flexibility changes in workflow during time new technologies should not require a new modeling

Decomposition horizontal and vertical (details) reusability parallel development

Simplicity understandable, not misinterpretable, better acceptance

Stability backwards compatibility, active development (future)

Traceability possibility to relive a workflow basic requirement for authentic digital objects



Workflow and the OAIS RM

OAIS RM standard for digital archives and framework for terminology, responsibilities, functional entities, logical data models

OAIS RM defines sevreal workflows mainly data flows serve as guideline



Workflow and the OAIS RM - Example



Representation Information I

a data object is interpreted using the representation information (remember OAIS)

representation information is information that maps a data object into a more meaningful concept

for example: ASCII definition describes how a sequence of bits is mapped into a symbol



Structures of Formats

Formats used for rendering, inspected by humans

Formats for automated processes Formats with unknown structure need a

software to interprete proprietary formats like MS Word Open Source software

Formats with known structure e.g. ASCII file



Formats - OAIS Layer Model



Semantics

meaning and relationships cause a hard problem

start with Data Dictionaries? add RDF (Resource Description Framework)?



Definition RDF

Resource Description Framework specification idea: making statements about resources in the form

of subject - predicate - object subject of an RDF statement is a resource e.g.

addressed by an URI (Unified Resource Identifier)



Information over the time

datasets changes over the time state may be important

take a snapshot of each moment in time and store it?

might result in a series of snapshots, additional representation information necessary (e.g. link from one snapshot to another)

annotations need to be stored (Why did they do it the way they did?)



Time Dependend Systems

there are time dependent systems, e.g. data bases

an implicit or explicit process might be associated

Emulation UVC (Universal Virtual Computer) JVM (Java Virtual Machine)



Questions

"Is saying 'It is XML' enough?" Does every archive need to do/store

everything?



Registries - About

a place to register a place to look up Example:

http://metadata.net/registries.html http://hul.harvard.edu/gdfr



Registry - Representation Information Labels I

digital object has an identifier pointing to representation information (Representation Information Label)

a data object is associated with one or more labels the label can have structure itself (it is itself a digital

object) on basis of the label the repository returns the

representation information registry needs to be searchable 'people' need to look up, whether representation

information is already in the registry



Registry - Representation Information Labels II



Registry - Representation Information Labels III

Structure of Representation Information Labels: http://dev.dcc.ac.uk/twiki/bin/view/Main/DCC

ApproachToCuration



Registry Access Solutions

Interface and protocols : JAXR can communicate with UDDI and ebXML FreebXML implementation

many access methods



JAXR - Definition

Java API for XML Registries provides a uniform and standard Java API for

accessing different kinds of XML Registries.



UDDI - Definition

Universal Description, Discovery and Integration

functions like a registry implemented using some kind of database companies or organisations may register their

services possibility to search for the service



ebXML I

Electronic Business Extended Markup Language

a set of specifications forming a modular electronic business framework

to conduct business with each other through the exchange of XML-based messages

ebXML uses a repository to store the information for international access

FreebXML offers sharing of free ebXML code



ebXML II



Persistent IDs

Need of persistent Ids Findability Which one to use?

DOI URN ARK PURL



Trusted Repositories

authenticity of representation information access control certification shared effort extensibility a format registry is not enough need of certification



Lecturers and Presentations of Delos Summer School I

Birte Christensen-Dalsgaard Head of Development at the State and University Library in Aarhus

Michael Day Research and Development team at UKOLN.

David Giaretta Associate Director for Development at the UK Digital Curation Centre.

Mariella Guercio, professor in archival science and electronic record management, ISTBAL, Università degli Studi di Urbino.

Ross Harvey inaugural Professor of Library and Information Management at Charles Sturt University’s School of Information Studies.

Stephan Heuscher, co-founder ikeep AG (Digital Archives Services).



Lecturers and Presentations of Delos Summer School II

Hans Hofman, co-director of ERPANET and senior advisor at the Nationaal Archief (National Archives) of the Netherlands.

Anne R. Kenney, Associate University Librarian for Instruction, Research, and Information Services at Cornell University Library.

Seamus Ross, Professor of Humanities Informatics and Digital Curation, and Director HATII (Humanities Advanced Technology and Information Institute) , University of Glasgow.

Andreas Rauber, Associate Professor at the Department of Software Technology and Interactive Systems at the Vienna University of Technology.

Manfred Thaller Professor of Historisch-Kulturwissenschaftliche Informationsverarbeitung, University of Cologne

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