Formal Foundations for the Evolution of Hypermedia Systems

1. 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)

2. 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.

3. 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

4. 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

5. 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

6. Memorisation SystemSpecification: Conceptual Structure CS (Graph) item, II concept, C association concepts, Ac association concept-item, Ai

7. 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

8. 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

9. 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

10. (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

11. 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

12. 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

13. Navigation System: Specification: SubGraph CSn

14. 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

15. Navigation System: Specification: Creating PN from RTn (Petri Nets)

16. 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

17. 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,

18. Navigation System: Evolution: Generating a new PN

19. 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

20. Specification formalisation

21. Evolution formalisation 1) Consistency 2) Propagation inside 3) Propagation outside

22. 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

23. 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).

24. 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?