PowerPoint-Pr

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A Theory for Model-based Transformation Applied
to Computer-Supported Preservation in Digital
Archives
Thomas Triebsees Universität der Bundeswehr
München Department of Computer Science Thomas.Tri
ebsees_at_unibw.de Tucson, 27th March 2007
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Agenda

1. Research Context
2. Motivating Example
3. Declarative, Preservation-Centric Approach for
   Model Transformation
4. Preservation Language
5. Results / Conclusions / Remarks

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Research Context

• Long-term preservation of digital material
• Two facets
• Preservation procedure
• Technical environment
• Preservation approaches
• Emulation
• Migration
• Hybrid
• Technical environment
• usually highly modularized and complex

preserve information
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Motivating Example
Customer
User
Archive
Archiver
Browser
extractMetadata
store
EXPOSE
UI
CI
BII
storePerm
respond
INGEST
REQUEST / RESPONSE
Permanent Storage
Web Storage
PStorage 1
PStorage 2
PStorage m
Server 1
Server 2
Server n
...
...
Transformation
Integratable into system specifications
Appropriate language elements
Abstraction from different implementations
Contribution Declarative, domain-specific,
preservation-centric language
that facilitates to specify preservation
requirements
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1. Declarative, Preservation-Centric Approach for
   Model Transformation

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Approach System Model and Transformation
Semantics
Model elements

• Typed Entities
• Associations
• Functions

Transformation algorithm sequence of basic
operations
basic operation (create object)
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Approach - Preservation
Concept ( semantic property)
implements
implements
specify pre- servation of


Context 1
Context n
defines
Constraints
Preservation language
used to generate / implement
respect
Transform. algorithms
source context
target context
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Example Abstraction through Contexts and
Concepts
Concept Website
Context AWeb
Context BWeb
AWeb
ltnamegt
src

Website

0..1
ltnamegt.html
f (FOPL)

eP
BWeb
1
1

ltnamegt
Folder
HTMLFile
0..1
1
1
ltnamegt.html
html




File
Tag

resources
trg

PDFFile

? (FOPL)

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Example Specifying the Preservation Task
Calculation
Concept Website
source
ltnamegt
start.html

AWeb

calculation2005
ltnamegt.html

calc.pdf
Website
0..1
overview
ltnamegt
eP
doclist.html
ltnamegt.html
1
1
HTMLFile
Folder
d
html
EXPOSE





resources
?
BWeb



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Example - Typed Entities
name String location String content Tag
start.html
HTMLFile
hHTML
lthtmlgt lthead/gt ltbodygt lta hrefgtlt/agt
lt/bodygt lt/htmlgt
start.html
lthtmlgt
t11Tag
ltheadgt
ltbodygt
t111Tag
t112Tag
name String attrs SeqltString x
Stringgt content Seqlt(String Taggt
Tag
lttitlegt
ltagt
t1121Tag
t1111Tag
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1. Preservation Language

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Preservation Language Transformation Constraints
h ? HTMLFile
h
h
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Preservation Language Object Preservation
Constraints
h ? HTMLFile
trans(d h ? h)
post(d) name(h) name(h)
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Preservation Language Concept Preservation
Constraints
presK(w ? Website, Website(w,f,h), AWeb, BWeb)
location, content
presO(h ? HTMLFile, hHTMLFile- )
Concept Website
Context AWeb
Context BWeb
d

Calculation

w Calculation
d(w) ____________
eP
eP

start.html
source

d(f) ________
d(h) __________


f source
h start.html


f html
f resources
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1. Results / Conclusion / Remarks

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Conclusion

• Constraint definitions show generality
  (abstraction
• from specification language)
• Prototypical implementation available
• Website migration example
• 300 files
• 20 concepts
• 700 constraints
• 2300 affected objects

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Conclusion

• Strengths
• State-based approach
• Powerful object model
• Abstraction via concepts specification language
  need not necessarily
• be FOPL
• Intuitive constraint definition for application
  domain
• Coherently formal underpinning
• Limits
• Generation of parallel migration algorithms
• Undecidability of FOPL
• Generating algorithms for comprehensive model
  reconstructions
• Efficiency

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Subject to your questions
?
Thomas Triebsees Universität der Bundeswehr
München Department of Computer Science Thomas.Tri
ebsees_at_unibw.de
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Constraint-based Migration
Advantages of declarative approach

• easily integratable into system specifications
• focus on critical issues
• abstraction from implementation, thus platform
  independent
• formal treatment possible

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Approach
Conceptual overview