Synchronisation of Model Visualisation and Code Generation Based on Model Transformation

The development, maintenance and documentation of complex systems is commonly supported by model-driven approaches where system properties are captured by visual models at different layers of abstraction and from different perspectives as proposed by the Object Management Group (OMG) and its model-driven architecture. Generally, a model is a concrete view on the system from a specific perspective in a particular domain. We focus on visual models in the form of diagrams and whose syntax is defined by domain-specific modelling languages (DSLs). Different models may represent different views on a system, i.e., they may be linked to each other by sharing a common set of information. Therefore, models that are expressed in one DSL may be transformed to interlinked models in other DSLs and furthermore, model updates may be synchronised between different domains. Concretely, this thesis presents the transformation and synchronisation of source code (abstract syntax trees, ASTs) written in the Satellite-Procedure & Execution Language (SPELL) to flow charts (code visualisation) and vice versa (code generation) as the result of an industrial case study. The transformation and synchronisation are performed based on existing approaches for model transformations and synchronisations between two domains in the theoretic framework of graph transformation where models are represented by graphs. Furthermore, extensions to existing approaches are presented for treating non-determinism in concurrent model synchronisations. Finally, the existing results for model transformations and synchronisations between two domains are lifted to the more general case of an arbitrary number of domains or models containing views, i.e., a model in one domain may be transformed to models in several domains or to all other views, respectively, and model updates in one domain may be synchronised to several other domains or to all other views, respectively

On Reasonable Space and Time Cost Models for the λ-Calculus

Slot and van Emde Boas Invariance Thesis states that a time (respectively, space) cost model is reasonable for a computational model C if there are mutual simulations between Turing machines and C such that the overhead is polynomial in time (respectively, linear in space). The rationale is that under the Invariance Thesis, complexity classes such as LOGSPACE, P, PSPACE, become robust, i.e. machine independent. In this dissertation, we want to find out if it possible to define a reasonable space cost model for the lambda-calculus, the paradigmatic model for functional programming languages. We start by considering an unusual evaluation mechanism for the lambda-calculus, based on Girard's Geometry of Interaction, that was conjectured to be the key ingredient to obtain a space reasonable cost model. By a fine complexity analysis of this schema, based on new variants of non-idempotent intersection types, we disprove this conjecture. Then, we change the target of our analysis. We consider a variant over Krivine's abstract machine, a standard evaluation mechanism for the call-by-name lambda-calculus, optimized for space complexity, and implemented without any pointer. A fine analysis of the execution of (a refined version of) the encoding of Turing machines into the lambda-calculus allows us to conclude that the space consumed by this machine is indeed a reasonable space cost model. In particular, for the first time we are able to measure also sub-linear space complexities. Moreover, we transfer this result to the call-by-value case. Finally, we provide also an intersection type system that characterizes compositionally this new reasonable space measure. This is done through a minimal, yet non trivial, modification of the original de Carvalho type system