title: Generic tools via general refinement

authors: Reeves, Steve

subjects: basis for tools

abstract: Tools have become essential in the formal model-driven development of software but are very time consuming to build and often restricted to a particular semantic interpretation of a particular syntax. This is regrettable since there is large amount in common between tools, even if they do “implement” different syntaxes and different semantics.
We propose splitting tools into front- and back-ends where an operational semantics acts as the link between the two. We will not have much to say about the front-end and the link in this paper since it is theoretically straightforward. Instead, we concentrate on the second part and provide a well-motivated, general, mathematical framework to form the underlying theory that gives great flexibility to the back-end of a tool which is concerned with developing software via stepwise refinement.
From a general model of refinement between two entities, where the refinement is parameterised on contexts and observations, we build logical theories which have refinement as implication. Further, we consider what can be expected of a guarantee concerning the behaviour of an implementation relative to a specification. Then by fixing the contexts and observations in suitable ways, and so getting particular, special models of refinement, we give a formal interpretation of a guarantee. To this we add theory morphisms between special models, where a theory morphism can change the contexts and observations we can make in controlled and useful ways, mainly by preserving a refinement relation between entities even as we change them.
We show how the generality brought about by the parameterisation allows an example from the literature, which seems formally not to be a refinement, to be captured as a refinement, in accordance with our intuitions about the example.
In this way we show the flexibility of our theory for a refinement tool back-end. From this it follows that the effort put into building a tool based on our theory will be well-spent—a single tool should be parameterised (just as our theory is) to deal with the many different notions of refinement found in the literature. Thus we make a contribution to the problem of ensuring correctness and dependability of software using formal methods and tools of modelling, design, verification and validation.

text: Generic tools via general refinement Tools have become essential in the formal model-driven development of software but are very time consuming to build and often restricted to a particular semantic interpretation of a particular syntax. This is regrettable since there is large amount in common between tools, even if they do “implement” different syntaxes and different semantics.
We propose splitting tools into front- and back-ends where an operational semantics acts as the link between the two. We will not have much to say about the front-end and the link in this paper since it is theoretically straightforward. Instead, we concentrate on the second part and provide a well-motivated, general, mathematical framework to form the underlying theory that gives great flexibility to the back-end of a tool which is concerned with developing software via stepwise refinement.
From a general model of refinement between two entities, where the refinement is parameterised on contexts and observations, we build logical theories which have refinement as implication. Further, we consider what can be expected of a guarantee concerning the behaviour of an implementation relative to a specification. Then by fixing the contexts and observations in suitable ways, and so getting particular, special models of refinement, we give a formal interpretation of a guarantee. To this we add theory morphisms between special models, where a theory morphism can change the contexts and observations we can make in controlled and useful ways, mainly by preserving a refinement relation between entities even as we change them.
We show how the generality brought about by the parameterisation allows an example from the literature, which seems formally not to be a refinement, to be captured as a refinement, in accordance with our intuitions about the example.
In this way we show the flexibility of our theory for a refinement tool back-end. From this it follows that the effort put into building a tool based on our theory will be well-spent—a single tool should be parameterised (just as our theory is) to deal with the many different notions of refinement found in the literature. Thus we make a contribution to the problem of ensuring correctness and dependability of software using formal methods and tools of modelling, design, verification and validation.

year: 2008

title: The language of certain conflicts of a nondeterministic process

authors: Malik, Robi

subjects: computer science

abstract: The language of certain conflicts is the most general set of behaviours of a nondeterministic process, which certainly lead to a livelock or deadlock when accepted by another process running in parallel. It is of great use in model checking to detect livelocks or deadlocks in very large systems, and in process-algebra to obtain abstractions preserving livelock and deadlock. Unfortunately, the language of certain conflicts is difficult to compute and has only been approximated in previous work. This paper presents an effective algorithm to calculate the language of certain conflicts for any given nondeterministic finite-state process and discusses its properties. The algorithm is shown to be correct and of exponential complexity.

text: The language of certain conflicts of a nondeterministic process The language of certain conflicts is the most general set of behaviours of a nondeterministic process, which certainly lead to a livelock or deadlock when accepted by another process running in parallel. It is of great use in model checking to detect livelocks or deadlocks in very large systems, and in process-algebra to obtain abstractions preserving livelock and deadlock. Unfortunately, the language of certain conflicts is difficult to compute and has only been approximated in previous work. This paper presents an effective algorithm to calculate the language of certain conflicts for any given nondeterministic finite-state process and discusses its properties. The algorithm is shown to be correct and of exponential complexity.

year: 2010-07-07

title: Schooling  for  'lesser beings'

authors: Holdom, Jim

subjects: Maori

abstract: Using Edward Said’s notion of ‘lesser beings’, it is argued that the political culture of schooling for Maori was and still is part of a pervasive Western European intellectual climate and culture which has a quite recent history, and which provided powerful support for the notion of Europe possessing a categorical superiority over all other continents, which in turn justified imperialism or neo-colonialism as civilising missions.
Racism and violence were endemic in colonialism and, despite the claimed moral high ground, were endemic in Aotearoa/New Zealand.  War was eulogised in the Native School system more than once.  The rise and demise of the World War II Maori War Organisation is illustrative of the rejection of Maori aspirations.  There were still no Maori in the senior echelons of the Maori Department in 1972.
The Native, later Maori, School system was overtly designed to 'Europeanise' Maori children and therefore Maori society.  Individualism was deeply embedded in English and set-tler thinking, whilst communal, ‘communist’ Maori society was to be destroyed.
The thesis examines images of colonialism, empire and imperialism in fiction and non-fiction, New Zealand and British, for adults and children, and notes the attitudes of think-ers like J S Mill and Darwin, of children’s authors Jules Verne and G H Henty, and of New Zealand author William Satchell.  The images continue, pervasive and endemic, in recent adult novels.  Science also played a role, as did history.
 Ranginui Walker, who is Maori, is the only historian to have written a history of New Zea-land which addressed the issue of waste lands, an issue on which Pakeha historians have a blind spot.  New Zealand encyclopedia do not index ‘waste land’ or ‘confiscation’.  Only two Waikato histories deal adequately, or even accurately, with confiscation, the central episode in the history of the Waikato.  Tourist material is equally illustrative.
The Native Schools section of the Education Department ran the Native Schools like a fiefdom, operating in legislative and regulatory black holes for the first thirty years and for much of the time after that.  Teachers were moved around at will.  
The practice of James H Pope, the first inspector of Native Schools, is closely and critically examined, and negatively assessed.  His official writings were consistently derogatory of Maori, and his decisions in respect of Te Kopua Native School were at times detrimental to the pupils.  Pope was a product of his times.
The Te Kopua record is closely scrutinised, and the practice of the Education Department is frequently found wanting.  It is probable that the establishment of the school was aimed to destabilise King Country Maori, not to benefit the children.  It is a story of Maori co-operation and contribution.
Part Two is a detailed partial biography of Te Kopua, it being argued that until there is a significant corpus of studies of Native Schools a valid history of the Native/Maori School system and of schooling for Maori is not possible

text: Schooling  for  'lesser beings' Using Edward Said’s notion of ‘lesser beings’, it is argued that the political culture of schooling for Maori was and still is part of a pervasive Western European intellectual climate and culture which has a quite recent history, and which provided powerful support for the notion of Europe possessing a categorical superiority over all other continents, which in turn justified imperialism or neo-colonialism as civilising missions.
Racism and violence were endemic in colonialism and, despite the claimed moral high ground, were endemic in Aotearoa/New Zealand.  War was eulogised in the Native School system more than once.  The rise and demise of the World War II Maori War Organisation is illustrative of the rejection of Maori aspirations.  There were still no Maori in the senior echelons of the Maori Department in 1972.
The Native, later Maori, School system was overtly designed to 'Europeanise' Maori children and therefore Maori society.  Individualism was deeply embedded in English and set-tler thinking, whilst communal, ‘communist’ Maori society was to be destroyed.
The thesis examines images of colonialism, empire and imperialism in fiction and non-fiction, New Zealand and British, for adults and children, and notes the attitudes of think-ers like J S Mill and Darwin, of children’s authors Jules Verne and G H Henty, and of New Zealand author William Satchell.  The images continue, pervasive and endemic, in recent adult novels.  Science also played a role, as did history.
 Ranginui Walker, who is Maori, is the only historian to have written a history of New Zea-land which addressed the issue of waste lands, an issue on which Pakeha historians have a blind spot.  New Zealand encyclopedia do not index ‘waste land’ or ‘confiscation’.  Only two Waikato histories deal adequately, or even accurately, with confiscation, the central episode in the history of the Waikato.  Tourist material is equally illustrative.
The Native Schools section of the Education Department ran the Native Schools like a fiefdom, operating in legislative and regulatory black holes for the first thirty years and for much of the time after that.  Teachers were moved around at will.  
The practice of James H Pope, the first inspector of Native Schools, is closely and critically examined, and negatively assessed.  His official writings were consistently derogatory of Maori, and his decisions in respect of Te Kopua Native School were at times detrimental to the pupils.  Pope was a product of his times.
The Te Kopua record is closely scrutinised, and the practice of the Education Department is frequently found wanting.  It is probable that the establishment of the school was aimed to destabilise King Country Maori, not to benefit the children.  It is a story of Maori co-operation and contribution.
Part Two is a detailed partial biography of Te Kopua, it being argued that until there is a significant corpus of studies of Native Schools a valid history of the Native/Maori School system and of schooling for Maori is not possible

year: 1998