The B Book

https://people.maths.ox.ac.uk/maini/PKM%20publications/282.pdf

Chaste: A test-driven approach to software development for biological modelling☆

Despite their widespread adoption, Role-based Access Control (RBAC) models exhibit certain shortcomings that make them less than ideal for deployment in, for example, distributed access control. In the distributed case, standard RBAC assumptions (e.g., of relatively static access policies, managed by human users, with complete information available about users and job functions) do not necessarily apply. Moreover, RBAC is restricted in the sense that it is based on one type of ascribed status, an assignment of a user to a role. In this article, we introduce the status-based access control (SBAC) model for distributed access control. The SBAC model (or family of models) is based on the notion of users having an action status as well as an ascribed status. A user's action status is established, in part, from a history of events that relate to the user; this history enables changing access policy requirements to be naturally accommodated. The approach can be implemented as an autonomous agent that reasons about the events, actions, and a history (of events and actions), which relates to a requester for access to resources, in order to decide whether the requester is permitted the access sought. We define a number of algebras for composing SBAC policies, algebras that exploit the language that we introduce for SBAC policy representation: identification-based logic programs. The SBAC model is richer than RBAC models and the policies that can be represented in our approach are more expressive than the policies admitted by a number of monotonic languages that have been hitherto described for representing distributed access control requirements. Our algebras generalize existing algebras that have been defined for access policy composition. We also describe an approach for the efficient implementation of SBAC policies.

Status-Based Access Control

The paper addresses theoretical and practical aspects of implementing multi-stage languages using abstract syntax trees (ASTs), gensym, and reflection. We present an operational account of the correctness of this approach, and report on our experience with a bytecode compiler called MetaOCaml that is based on this strategy. Current performance measurements reveal interesting characteristics of the underlying OCaml compiler, and illustrate why this strategy can be particularly useful for implementing domain-specific languages in a typed, functional setting.

Implementing multi-stage languages using ASTs, Gensym, and reflection

2003 0 Gerwin Klein, and Tobias Nipkow; Verified Bytecode Verifiers; Theoretical Computer Science, 298:583-626; 2003. 1 S. Berghofer, and M. Strecker; Extracting a formally verified, fully executable compiler from a proof assistant; In Proceedings of Compiler Optimization meet Compiler Verification; 2003. 2 Sabine Glesner, and Jan Olaf Blech; Classifying and Formally Verifying Integer Constant Folding; In Proceedings of Compiler Optimization meet Compiler Verification; 2003. 3 Thomas Genet, Thomas Jensen, Vikash Kodati, and David Pichardie; A Java Card CAP Converter in PVS; In Proceedings of Compiler Optimization meet Compiler Verification; 2003.

Compiler verification: a bibliography

We describe the use of a flexible meta-interpreter for performing access control checks on deductive databases. The meta-program is implemented in Prolog and takes as input a database and an access policy specification. We then proceed to specialise the meta-program for a given access policy and intensional database by using the logen partial evaluation system. In addition to describing the programs involved in our approach, we give a number of performance measures for our implementation of an access control checker, and we discuss the implications of using this approach for access control on deductive databases. In particular, we show that by using our approach we get flexible access control with virtually zero overhead.

/pdf/efficient-and-flexible-access-control-via-logic-program-4zp8bs2sqy.pdf

Efficient and flexible access control via logic program specialisation

We present ECCE and LOGEN, two partial evaluators for Prolog using the online and offline approach respectively. We briefly present the foundations of these tools and discuss various applications. We also present new implementations of these tools, carried out in Ciao Prolog. In addition to a command-line interface new user-friendly web interfaces were developed. These enable non-expert users to specialise logic programs using a web browser, without the need for a local installation.

/pdf/the-ecce-and-logen-partial-evaluators-and-their-web-g52qdijhhu.pdf

The Ecce and Logen partial evaluators and their web interfaces

This paper presents a new modelling technique capable of modelling both control and data information using a single unified approach. This is achieved by modifying the classical Petri Net structure, allowing it to have two types of transitions and arcs. As a consequence, loops and conditional operations within complex specifications are easily identified. The system dynamic behaviour is modelled using a new marking scheme of the net consisting of a new element called value for data representation in addition to classical tokens used for control purpose. Structural definitions, behavioural rules and graphical representation of the new modelling technique are given. One potential application of the proposed modelling technique is the internal representation of embedded systems specification. Two examples are included illustrating the applicability and efficiency of the proposed modelling technique.

/pdf/dual-transitions-petri-net-based-modelling-technique-for-1liqr6f2zp.pdf

Dual transitions petri net based modelling technique for embedded systems specification

This paper addresses the interrelation between control and data flow in embedded system models through a new design representation, called Dual Flow Net (DFN). A modeling formalism with a very close-fitting control and data flow is achieved by this representation, as a consequence of enhancing its underlying Petri net structure. The work presented in this paper does not only tackle the modeling side in embedded systems design, but also the validation of embedded system models through formal methods. Various introductory examples illustrate the applicability of the DFN principles, whereas the capability of the model to with complex designs is demonstrated through the design and verification of a real-life Ethernet coprocessor.

/pdf/dual-flow-nets-modeling-the-control-data-flow-relation-in-3wtkoaj7yd.pdf

Dual Flow Nets: Modeling the control/data-flow relation in embedded systems

We describe the use of a flexible meta-interpreter for performing access control checks on deductive databases. The meta-program is implemented in Prolog and takes as input a database and an access policy specification. For processing access control requests we specialise the meta-program for a given access policy and database by using the logen partial evaluation system. The resulting specialised control checking program is dependent solely upon dynamic information that can only be known at the time of actual access request evaluation. In addition to describing our approach, we give a number of performance measures for our implementation of an access control checker. In particular, we show that by using our approach we get flexible access control with virtually no overhead, satisfying the Jones optimality criterion. The paper also shows how to satisfy the Jones optimality criterion more generally for interpreters written in the non-ground representation.

/pdf/efficient-and-flexible-access-control-via-jones-optimal-3py6rerxd9.pdf

Mauricio Varea

Papers

Efficient and flexible access control via logic program specialisation

The Ecce and Logen partial evaluators and their web interfaces

Dual transitions petri net based modelling technique for embedded systems specification

Dual Flow Nets: Modeling the control/data-flow relation in embedded systems

Efficient and flexible access control via Jones-optimal logic program specialisation