thomas triebsees universität der bundeswehr münchen department of computer science
DESCRIPTION
A Theory for Model-based Transformation Applied to Computer-Supported Preservation in Digital Archives. Thomas Triebsees Universität der Bundeswehr München Department of Computer Science [email protected] Tucson, 27th March 2007. Agenda. Research Context Motivating Example - PowerPoint PPT PresentationTRANSCRIPT
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 1
Thomas TriebseesUniversität der Bundeswehr München
Department of Computer Science
Tucson, 27th March 2007
A Theory for Model-based TransformationApplied to Computer-SupportedPreservation in Digital Archives
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 2
Agenda
I. Research Context
II. Motivating Example
III. Declarative, Preservation-Centric Approach for Model Transformation
IV. Preservation Language
V. Results / Conclusions / Remarks
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 3
Research Context
Long-term preservation of digital material
Two facets:
o Preservation procedure
o Technical environment
Preservation approaches:
o Emulation
o Migration
o Hybrid
Technical environment
o usually highly modularized and complex
} preserve information
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 4
Motivating Example
PStorage 1 PStorage 2 PStorage m
...Server 1
...
Archiver Browser
Server 2 Server n
UICIINGEST REQUEST /RESPONSE
EXPOSE BII
ArchiveCustomer User
Permanent Storage Web Storage
storePerm
extractMetadata store
respond
TransformationTransformation
Contribution: Declarative, domain-specific, preservation-centric language that facilitates to specify preservation requirements
Integratable into system specifications
Appropriate language elements
Abstraction from differentimplementations
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 5
III. Declarative, Preservation-Centric Approach for Model Transformation
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 6
Approach – System Model and Transformation Semantics
-Typed Entities
-Associations
-Functions
Model elements
Archive State AArchive State ASystem State A Archive State A'Archive State A'System State A'
basic operation(create object)
System State A''
basic operation(set association)
Transformation algorithm = sequence of basic operationsTransformation algorithm = sequence of basic operations
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 7
Approach - Preservation
Preservation Preservation languagelanguage
ConstraintsConstraints
Transform.Transform.algorithmsalgorithms
defines
used togenerate /implement
respect
Concept (= semantic property)Concept (= semantic property)
Context 1Context 1 Context nContext n…
source context target context
implements implements
…specify pre-servation of
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 8
Example – Abstraction through Contexts and Concepts
Website
HTMLFileFolder
File
PDFFile
Tag
eP
0..1
11
1
*
1
*
*
0..1
<name>
<name>.html
<name>
html
resources
<name>.html
Concept Website
……
…
……
…
……
…
src
trg
Context AWebContext BWeb
φ (FOPL)
ψ (FOPL)
AWeb
BWeb
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 9
Example – Specifying the Preservation Task
source
calculation2005
overview
calc.pdf
doclist.html
start.html
Website
eP
0..1
<name>
<name>.html
<name>
html
resources
<name>.html
……
…
……
…
……
…
AWeb
??
HTMLFileFolder
11
… …
δ
Concept Website
BWeb
Calculation
EXPOSE
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 10
Example - Typed Entities
name : Stringattrs : Seq<String x String>content : Seq<(String | Tag>
name : Stringattrs : Seq<String x String>content : Seq<(String | Tag>
Tag
<html><head/>
<body> … <a href=“…“></a> …</body></html>
<html><head/>
<body> … <a href=“…“></a> …</body></html>
start.html name : Stringlocation : Stringcontent : Tag
name : Stringlocation : Stringcontent : Tag
HTMLFile start.htmlstart.html
h:HTMLh:HTML
<html><html>
t11:Tagt11:Tag
<head><head>
t111:Tagt111:Tag<body><body>
t112:Tagt112:Tag
<title><title>
t1111:Tagt1111:Tag
<a><a>
t1121:Tagt1121:Tag
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IV. Preservation Language
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 12
Preservation Language – Transformation Constraints
h → HTMLFile
name = "start.html"location = "/… /source"content = <...>
name = "start.html"location = "/… /source"content = <...>
h:HTMLFile
name = ?location = ?content = ?
name = ?location = ?content = ?
δ(h):HTMLFileδ
trans(δ | h → h‘)trans(δ | h → h‘)
Archive State A'Archive State A'System State A Archive State A'Archive State A'System State A'
h h‘
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 13
HTMLFile-{ }
name
location,content
name = "start.html"location = "/… /source"content = <...>
name = "start.html"location = "/… /source"content = <...>
h:HTMLFile
Preservation Language – Object Preservation Constraints
name = "start.html"location = ?content = <...>
name = "start.html"location = ?content = <...>
δ(h):HTMLFile
δ
name
trans(δ | h → h‘)trans(δ | h → h‘)
h → HTMLFile
post(δ) ≡ { name(h‘) = name(h) }
presO(h → HTMLFile, h[HTMLFile-{ }])location,content
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 14
Preservation Language – Concept Preservation
Constraints
w: „Calculation“
f: „source“
Context AWeb
δ
presK({w → Website}, Website(w,f,h), AWeb, BWeb)
Concept Website
h: „start.html“
eP
δ(w): ____________
δ(f): ________ δ(h): __________
eP
Context BWeb
f‘: „html“ f‘‘: „resources“
presO(h → HTMLFile, h[HTMLFile-{ }])location, content
„start.html“„source“
„Calculation“
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V. Results / Conclusion / Remarks
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 16
Conclusion
Constraint definitions show generality (abstraction
from specification language)
Prototypical implementation available
Website migration example:o ≈ 300 files
o ≈ 20 concepts
o ≈ 700 constraints
o ≈ 2300 affected objects
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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 17
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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Thomas Triebsees, Uwe M. Borghoff, Dptmt. of Computer Science 18
Subject to your questions…
Thomas TriebseesUniversität der Bundeswehr München
Department of Computer Science
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Constraint-based Migration
easily integratable into system specifications
focus on critical issues
abstraction from implementation, thus platform independent
formal treatment possible
Advantages of declarative approach
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Approach
Conceptual overview
(1) Pre-processing
object model
source modelinstance
(4) Algorithm execution
target objectmodel
(2) Concept recognition
concept def.
extendedobject model
(3) Algorithm generation
constraints
migration alg.
(5) Post-processing
target modelinstance