Formal Foundations for the Evolution of Hypermedia Systems

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Formal Foundations for the Evolution of
Hypermedia Systems

• Mª José Rodríguez-Fórtiz (Universidad de Granada)
• Lina García-Cabrera (Universidad de Jaén)
• José Parets-Llorca (Universidad de Granada)

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Why Evolutionary Hypermedia?

• Dynamic and evolving nature of Hp Systems.
• Represents a conceptual domain
• Ways of representing, structuring and browsing
  it.
• Life-cycle- of Hp is not sufficiently considered.
  
• Implicit, diluted and unaffordable structuring
  process inside the documents.

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A Semantic-Dynamic Model based on Systems

• Memorisation system
• information semantics, conceptual domain.

Navigation system extends semantics, order
relationships to cover the conceptual domain.

• Evolution
• Changes and updates integrated in the development
  process

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Formalisms of a Higher Abstraction Level
Meta-level Evolution operations
(Ace) (meta-operations with preconditions or
meta-restrictions)
changes
changes
Memorisation System MS (CS, RT) concepts,
items, associations, restrictions
Navigation System NS (CSn , RTn,
PN) navigation rules or restrictions
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Formalisms of a Higher Abstraction Level
Meta-level Evolution operations
(Ace) (meta-operations with preconditions or
meta-restrictions)
changes
changes
Memorisation System MS (CS, RT) concepts,
items, associations, restrictions
Navigation System NS (CSn , RTn,
PN) navigation rules or restrictions
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Memorisation SystemSpecification Conceptual
Structure CS
(Graph)
item, II
concept, C
association concepts, Ac
association concept-item, Ai
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Memorisation SystemSpecification Restrictions
RTs RTa

• (Temporal logic)
• RTs is_a association is not recursive
• ltc, is_a, c1gt ? not ? ltc1, is_a, cgt ? c, c1 ? C
• RTa every planet will rotate around the sun
• ltc, rotate, Sungt ? ? ltc, is_a, Planetsgt ? c?
  C

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Formalisms of a Higher Abstraction Level
Meta-level Evolution operations
(Ace) (meta-operations with preconditions or
meta-restrictions)
changes
changes
Memorisation System MS (CS, RT) concepts,
items, associations, restrictions
Navigation System NS (CSn , RTn,
PN) navigation rules or restrictions
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Memorisation SystemEvolution Modification of CS
(Set-theory)
(Set-theory or Temporal logic)

• Ace
• add_concept Saturn
• Meta-RT
• Saturn ? C

• Ace
• add_concept_assoc
• ltSaturn, is_a, Planets gt
• Meta-RT (set-theory)
• lt Planets, is_a, Saturn gt ? Ac
• (temporal logic)
• ltc, is_a, c1gt ? not ? ltc1, is_a, cgt with c
  Saturn and c1 Planets

Internal propagation of the changes

• Evolving MS
• CS ? CS'
• CS' (C', II', Ac', Ai')
• C' C ? Saturn II' II Ac' Ac ? ltPlanets,
  is_a, Saturngt Ai' Ai

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Memorisation SystemEvolution Modification of
RTa

• (Predicate temporal logic)
• Ace addRest (ltc,is_a,Planetsgt? ?
  ltc,rotate,Sungt)
• Meta-RT cycles in concept associations are not
  allowed
• addRest(ac2, ac1)? not ? isRest(ac1,ac2)
  ac1,ac2? Ac
• This clause can be instantiated
• addRest (ltc, rotate, Sungt, ltc, is_a, Planetsgt)
  ?
• not ? isRest(ltc, is_a, Planetsgt,
  ltc,rotate, Sungt)

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Memorisation SystemSpecification Restrictions
RTs RTa

• (Temporal logic)
• RTs is_a association is not recursive
• ltc, is_a, c1gt ? not ? ltc1, is_a, cgt ? c, c1 ? C
• RTa every planet will rotate around the sun
• ltc, rotate, Sungt ? ? ltc, is_a, Planetsgt ? c?
  C

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Formalisms of a Higher Abstraction Level
Meta-level Evolution operations
(Ace) (meta-operations with preconditions or
meta-restrictions)
changes
changes
Memorisation System MS (CS, RT) concepts,
items, associations, restrictions
Navigation System NS (CSn , RTn,
PN) navigation rules or restrictions
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Navigation System Specification SubGraph CSn
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Navigation System Specification Restrictions
RTn

• (Temporal logic)
• RTn
• c.Portugal.map ? ? c.Countries.list and a.is_a
• c.Portugal.map ? ? c.Countries.cities and a.is_a
• c.Portugal.history ? ? c.Countries.cities and
  a.is_a

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Navigation System Specification Creating PN
from RTn
(Petri Nets)
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Formalisms of a Higher Abstraction Level
Meta-level Evolution operations
(Ace) (meta-operations with preconditions or
meta-restrictions)
changes
changes
Memorisation System MS (CS, RT) concepts,
items, associations, restrictions
Navigation System NS (CSn , RTn,
PN) navigation rules or restrictions
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Navigation System Evolution Modification of
RTn

• (Predicate temporal logic)
• Ace
• delRest ( c.Portugal.map ? ? c.Countries.list
  and a.is_of )
• Meta-RT Every item must be reachable
• delRest(c.i, nav_rest) ? ? existRest(c.i,
  nav_rest1) or ? ( existRest(c1.i1, nav_rest2)
  and ref(nav_rest2, c.i) ) ? c ? C , ? i
  ? II,

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Navigation System Evolution Generating a new
PN
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Evolution and flexibility
Different ways of representing, structuring and
browsing the same Information System
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Specification formalisation
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Evolution formalisation
1) Consistency 2) Propagation inside 3)
Propagation outside
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Evolving Actions
5) CS evolves (Set Theory) 6) RTa evolve
(PTL) 7) If RTa change --gt CS changes 8) RTn
evolve (PTL)
1) RTs or RTa lt--gt CS 2) CSn, subset of the CS
If CS changes --gt CSn changes 3) RTn
constraint CSn 4) PN created from RTn. If
RTn change --gt PN changes
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Conclusions

• MS and NS allow a specification and management of
  the semantics of information and its navigation
  in a separated way, using different formalisms.
• The model guarantees the conservation of the
  integrity of the system by meta-restrictions.
• Evolution actions inside and outside each system.
• The selected formalisms allow an easy
  specification and change of the structure of each
  system.
• These evolution formalisms can also be applied to
  other evolving systems (reactive or temporal
  ones).

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Suggestions for discussion topics

• Evolution during the development process.
• Specification and evolution relationships.
• Evolution (changes in the structure)
• Meta-level.
• Guarantee of consistency invariants, pre or
  postconditions.
• Change impact, propagation of the change.
• Which formalism is the better?