Jovanka Pantovic

Types for role-based access control of dynamic web data

We introduce a role-based access control calculus for modelling dynamic web data and a corresponding type system. It is an extension of the Xdp calculus proposed by Gardner and Maffeis. In our framework, a network is a parallel composition of locations, where each location contains processes with roles and a data tree whose edges are associated with roles. Processes can communicate, migrate from a location to another, use the data, change the data and the roles in the local tree. In this way, we obtain a model that controls process access to data. We propose a type system which ensures that a specified network policy is respected during computations. Finally, we show that our calculus obeys the following security properties: (1) all data trees and processes with roles in a location agree with the location policy; (2) a process can migrate only to a location with whose policy it agrees; (3) a process with roles can read and modify only data which are accessible to it; (4) a process with roles can enable and disable roles in agreement with the location policy.

Minimal partial hyperclones on a two-element set

Let A be a two-element set. It has been proven by Machida that the lattice of hyperclones has continuum cardinality. The current paper first determines all the minimal partial hyperclones. Following this, the authors give all three-element subsets of minimal hyperoperations whose union generates the clone of all hyperoperations as well as all four minimal subsets of minimal partial hyperoperations whose union generates the clone of all partial hyperoperations.

Combining behavioural types with security analysis

Todays software systems are highly distributed and interconnected, and they increasingly rely on communication to achieve their goals; due to their societal importance, security and trustworthiness are crucial aspects for the correctness of these systems. Behavioural types, which extend data types by describing also the structured behaviour of programs, are a widely studied approach to the enforcement of correctness properties in communicating systems. This paper offers a unified overview of proposals based on behavioural types which are aimed at the analysis of security properties.

Precise subtyping for synchronous multiparty sessions

The notion of subtyping has gained an important role both in theoretical and applicative domains: in lambda and concurrent calculi as well as in programming languages. The soundness and the completeness, together referred to as the preciseness of subtyping, can be considered from two different points of view: operational and denotational. The former preciseness has been recently developed with respect to type safety, i.e. the safe replacement of a term of a smaller type when a term of a bigger type is expected. The latter preciseness is based on the denotation of a type which is a mathematical object that describes the meaning of the type in accordance with the denotations of other expressions from the language. The result of this paper is the operational and denotational preciseness of the subtyping for a synchronous multiparty session calculus. The novelty of this paper is the introduction of characteristic global types to prove the operational completeness.

Separating Points by Parallel Hyperplanes— Characterization Problem

This paper deals with partitions of a discrete set S of points in a d-dimensional space, by h parallel hyperplanes. Such partitions are in a direct correspondence with multilinear threshold functions which appear in the theory of neural networks and multivalued logic. The characterization (encoding) problem is studied. We show that a unique characterization (encoding) of such multilinear partitions of S = {0,1,..., m - 1}d is possible within O(h ldr d2 ldr log to) bit rate per encoded partition. The proposed characterization (code) consists of(d+l)ldr(h+l) discrete moments having the order no bigger than 1. The obtained bit rate is evaluated depending on the mutual relations between h, d, and m. The optimality is reached in some cases.

On the partial hyperclone lattice

For any finite set A, the partial clone lattice on A is embedded into the partial hyperclone lattice on A. It is shown that there are maximal intervals in the partial hyperclone lattice and there are four minimal partial hyperclones such that their join contains all partial hyperoperations. It is proved in (T. Drescher et al., 2001) that the mapping /spl lambda/ from the lattice of partial hyperclones on A into the lattice of clones of operations on P(A) defined by /spl lambda/(C)=/spl delta/(C/sup #/), where /spl delta/(C/sup #/) is the clone of operations on P(A) generated by C/sup #/, is an order embedding, but not a full one. In this paper, it is proved that there are continuum many clones of operations on P(A) that are in the interval [/spl lambda/(J/sub A/), /spl lambda/(Hp/sub A/)] but these are not in the set im/spl lambda/ of all images of the mapping /spl lambda/, where J/sub A/ is the set of all (partial) hyperprojections and Hp/sub A/ is the set of all partial hyperoperations on A.

Dynamic role authorization in multiparty conversations

Protocols in distributed settings usually rely on the interaction of several parties and often identify the roles involved in communications. Roles may have a behavioral interpretation, as they do not necessarily correspond to sites or physical devices. Notions of role authorization thus become necessary to consider settings in which, e.g., different sites may be authorized to act on behalf of a single role, or in which one site may be authorized to act on behalf of different roles. This flexibility must be equipped with ways of controlling the roles that the different parties are authorized to represent, including the challenging case in which role authorizations are determined only at runtime. We present a typed framework for the analysis of multiparty interaction with dynamic role authorization and delegation. Building on previous work on conversation types with role assignment, our formal model is based on an extension of the

Dynamic Role Authorization in Multiparty Conversations

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