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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). Why Evolutionary Hypermedia?. Dynamic and evolving nature of Hp 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)
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.
Memorisation system: information semantics, conceptual domain. A Semantic-Dynamic Model based on Systems Navigation system: extends semantics, order relationships to cover the conceptual domain. Evolution Changes and updates integrated in the development process
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
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
Memorisation SystemSpecification: Conceptual Structure CS (Graph) item, II concept, C association concepts, Ac association concept-item, Ai
Memorisation SystemSpecification: Restrictions RTs & RTa (Temporal logic) • RTs: “is_a association is not recursive” <c, is_a, c1> not <c1, is_a, c> c, c1 C • RTa: “every planet will rotate around the sun” <c, rotate, Sun> <c, is_a, Planets> c C
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
Ace: add_concept_assoc: <Saturn, is_a, Planets > Meta-RT: (set-theory) < Planets, is_a, Saturn > Ac (temporal logic) <c, is_a, c1> not <c1, is_a, c> with c = Saturn and c1= Planets Ace: add_concept: Saturn Meta-RT: Saturn C Memorisation SystemEvolution: Modification of CS (Set-theory) (Set-theory or Temporal logic) Internal propagation of the changes Evolving MS: CS CS' CS' = (C', II', Ac', Ai') C'= C {Saturn}; II' = II ; Ac'= Ac {<Planets, is_a, Saturn>}; Ai' = Ai
(Predicate temporal logic) Ace: addRest (<c,is_a,Planets> <c,rotate,Sun>) 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 (<c, rotate, Sun>, <c, is_a, Planets>) not isRest(<c, is_a, Planets>, <c,rotate, Sun>) Memorisation SystemEvolution: Modification of RTa
Memorisation SystemSpecification: Restrictions RTs & RTa (Temporal logic) • RTs: “is_a association is not recursive” <c, is_a, c1> not <c1, is_a, c> c, c1 C • RTa: “every planet will rotate around the sun” <c, rotate, Sun> <c, is_a, Planets> c C
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
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
Navigation System: Specification: Creating PN from RTn (Petri Nets)
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
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,
PN111 . . . PN11n CSn11 . . . CSn1n CSm1 . . . CSmn PN1n1 . . . PN1nn Information System PNn11 . . . PNn1n CSnn1 . . . CSnnn PNnn1 . . . PNnnn Evolution and flexibility Different ways of representing, structuring and browsing the same Information System
Evolution formalisation 1) Consistency 2) Propagation inside 3) Propagation outside
Evolving Actions 5)CS evolves (Set Theory) 6)RTa evolve (PTL) 7) If RTa change --> CS changes 8)RTn evolve (PTL) 1)RTsor RTa <--> CS 2)CSn, subset of the CS If CS changes --> CSn changes 3)RTn constraint CSn 4)PN created from RTn. If RTn change --> PN changes
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).
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?