Flavio Ferrarotti

Flavio Ferrarotti
Software Competence Center Hagenberg | SCCH

Doctor of Philosophy

About

41
Publications
1,082
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149
Citations

Publications

Publications (41)
Article
Full-text available
It is well-known that polylogarithmic space (PolyL for short) does not have complete problems under logarithmic space many-one reductions. Thus, we propose an alternative notion of completeness inspired by the concept of uniformity studied in circuit complexity theory. We then prove the existence of a uniformly complete problem for PolyL under this...
Article
Message Queuing Telemetry Transport (MQTT) is the most widely used protocol within the communication layer of the Internet of Things (IoT). Message brokers are a key component of the MQTT protocol and a single point of failure. Incompatibilities between different MQTT brokers or broker versions with their clients can cause critical failures and bec...
Article
Full-text available
Following the stimulating discussions in the workshops held during the 9th International Conference on Model and Data Engineering (MEDI 2019), we proposed to edit a special issue compiling the fruitful research resulting from those discussions. This special issue on current research in model and data engineering of the Journal of Universal Computer...
Chapter
In this paper we use the Abstract State Machine (ASM) method for high-level system design and analysis created by Egon Börger to formally specify Grover’s quantum database search algorithm, stepwise refining it from its highest abstraction level down to its implementation as a quantum circuit. Our aim is to raise the question of whether the ASM met...
Article
Reflective algorithms are algorithms that can modify their own behaviour. Recently a behavioural theory of reflective algorithms has been developed, which shows that they are captured by reflective abstract state machines (rASMs). Reflective ASMs exploit extended states that include an updatable representation of the ASM signature and rules to be e...
Article
We propose logical characterizations of problems solvable in deterministic polylogarithmic time (PolylogTime) and polylogarithmic space (PolylogSpace). We introduce a novel two-sorted logic that separates the elements of the input domain from the bit positions needed to address these elements. We prove that the inflationary and partial fixed point...
Preprint
Full-text available
Complexity theory can be viewed as the study of the relationship between computation and applications, understood the former as complexity classes and the latter as problems. Completeness results are clearly central to that view. Many natural algorithms resulting from current applications have polylogarithmic time (PolylogTime) or space complexity...
Chapter
Message Queuing Telemetry Transport (MQTT) protocol is among the preferred publish/subscribe protocols used for Machine-to-Machine (M2M) communication and Internet of Things (IoT). Although the MQTT protocol itself is quite simple, the concurrent iteration of brokers and clients and its intrinsic non-determinism, coupled with the diversity of platf...
Chapter
Distributed Denial-of-Service attacks are a dramatically increasing threat to Internet-based services and connected devices. In the form of reflection attacks they are abusing other systems to perform the actual attack, often with an additional amplification factor. In this work we describe a reflection attack exploiting the industrial Message Queu...
Article
We are interested in specifications which provide a consistent high-level view of systems. They should abstract irrelevant details and provide a precise and complete description of the behaviour of the system. This view of software specification can naturally be expressed by means of Gurevich’s Abstract State Machines (ASMs). There are many known b...
Chapter
Reflective algorithms are algorithms that can modify their own behaviour. Recently a behavioural theory of reflective algorithms has been developed, which shows that they are captured by reflective abstract state machines (rASMs). Reflective ASMs exploit extended states that include an updatable representation of the ASM signature and rules to be e...
Article
We introduce a restricted second-order logic $\textrm{SO}^{\textit{plog}}$ for finite structures where second-order quantification ranges over relations of size at most poly-logarithmic in the size of the structure. We demonstrate the relevance of this logic and complexity class by several problems in database theory. We then prove a Fagin’s style...
Preprint
Full-text available
We develop a behavioural theory of reflective sequential algorithms (RSAs), i.e. sequential algorithms that can modify their own behaviour. The theory comprises a set of language-independent postulates defining the class of RSAs, an abstract machine model, and the proof that all RSAs are captured by this machine model. As in Gurevich's behavioural...
Chapter
The polylogarithmic time hierarchy structures sub-linear time complexity. In recent work it was shown that all classes or () in this hierarchy can be captured by semantically restricted fragments of second-order logic. In this paper the descriptive complexity theory of polylogarithmic time is taken further showing that there are strict hierarchies...
Preprint
Full-text available
The polylogarithmic time hierarchy structures sub-linear time complexity. In recent work it was shown that all classes $\tilde{\Sigma}_{m}^{\mathit{plog}}$ or $\tilde{\Pi}_{m}^{\mathit{plog}}$ ($m \in \mathbb{N}$) in this hierarchy can be captured by semantically restricted fragments of second-order logic. In this paper the descriptive complexity t...
Preprint
Full-text available
We introduce a restricted second-order logic $\mathrm{SO}^{\mathit{plog}}$ for finite structures where second-order quantification ranges over relations of size at most poly-logarithmic in the size of the structure. We demonstrate the relevance of this logic and complexity class by several problems in database theory. We then prove a Fagin's style...
Chapter
We are interested in specifications which provide a consistent high-level view of systems. They should abstract irrelevant details and provide a precise and complete description of the behaviour of the system. This view of software specification can naturally be expressed by means of Gurevich’s Abstract State Machines (ASMs). There are many known b...
Article
The bulk synchronous parallel (BSP) bridging model is a model for concurrent computations with alternating computation and communication phases between programs running on different processors. In a computation phase the programs proceed independently and asynchronously until a barrier is reached. In a communication phase initiated by all programs...
Chapter
We propose a logical characterization of problems solvable in deterministic polylogarithmic time (\(\mathrm {PolylogTime}\)). We introduce a novel two-sorted logic that separates the elements of the input domain from the bit positions needed to address these elements. In the course of proving that our logic indeed captures \(\mathrm {PolylogTime}\)...
Preprint
Full-text available
We propose a logical characterization of problems solvable in deterministic polylogarithmic time (PolylogTime). We introduce a novel, two-sorted logic that separates the elements of the input domain from the bit positions needed to address these elements. In the course of proving that our logic indeed captures PolylogTime on finite ordered structur...
Book
This book constitutes the thoroughly refereed papers of the workshops held at the 9th International Conference on New Trends in Model and Data Engineering, MEDI 2019, in Toulouse, France, in October 2019. The 12 full and the three short workshop papers presented together with one invited paper were carefully reviewed and selected from 35 submissio...
Article
Full-text available
We develop a logic which enables reasoning about single steps of non-deterministic and parallel Abstract State Machines (ASMs). Our logic builds upon the unifying logic introduced by Nanchen and Stärk for reasoning about hierarchical (parallel) ASMs. Our main contribution is the handling of non-determinism within the logical formalism. We do this w...
Chapter
The Resource Description Framework (RDF) is a simple, but frequently used W3C standard, which uses triplets to define relationships between resources. In this paper the evaluation of queries in the query language SPARQL on RDF data with meta-data is investigated. We first show that if the data are stratified, i.e. a particular partial order can be...
Preprint
Full-text available
Let $\mathrm{SO}^{\mathit{plog}}$ denote the restriction of second-order logic, where second-order quantification ranges over relations of size at most poly-logarithmic in the size of the structure. In this article we investigate the problem, which Turing machine complexity class is captured by Boolean queries over ordered relational structures tha...
Article
Full-text available
Second-order transitive-closure logic, SO(TC), is an expressive declarative language that captures the complexity class PSPACE. Already its monadic fragment, MSO(TC), allows the expression of various NP-hard and even PSPACE-hard problems in a natural and elegant manner. As SO(TC) offers an attractive framework for expressing properties in terms of...
Chapter
We develop a behavioural theory of reflective sequential algorithms (RSAs), i.e. algorithms that can modify their own behaviour. The theory comprises a set of language-independent postulates characterising the class of RSAs, an abstract machine model that provably satisfies the postulates, and a proof that all RSAs are captured by this machine mode...
Article
In database theory, the term database transformation was used to refer to a unifying treatment for computable queries and updates. Recently, it was shown that non-deterministic database transformations can be captured exactly by a variant of ASMs, the so-called Database Abstract State Machines (DB-ASMs). In this article we present a logic for DB-AS...
Conference Paper
We define new fragments of higher-order logics of order three and above, and investigate their expressive power over finite models. The key unifying property of these fragments is that they all admit inexpensive algorithmic translations of their formulae to equivalent second-order logic formulae. That is, within these fragments we can make use of t...
Conference Paper
A concurrent system can be characterised by autonomously acting agents, where each agent executes its own program, uses shared resources and communicates with the others, but otherwise is totally oblivious to the behaviour of the other agents. In an evolving concurrent system agents may change their programs, enter or leave the collection at any ti...
Article
Full-text available
In the framework of computable queries in Database Theory, there are many examples of queries to (properties of) relational database instances that can be expressed by simple and elegant third order logic ($\mathrm{TO}$) formulae. In many of those properties the expressive power of $\mathrm{TO}$ is not required, but the equivalent second order logi...
Conference Paper
Full-text available
Starting from Gurevich’s thesis for sequential algorithms (the so-called “sequential ASM thesis”), we propose a characterization of the behaviour of sequential algorithms enriched with reflection. That is, we present a set of postulates which we conjecture capture the fundamental properties of reflective sequential algorithms (RSAs). Then we look a...
Conference Paper
We develop a logic which enables reasoning about single steps of non-deterministic parallel Abstract State Machines (ASMs). Our logic builds upon the unifying logic introduced by Nanchen and Stärk for reasoning about hierarchical (parallel) ASMs. Our main contribution to this regard is the handling of non-determinism (both bounded and unbounded) wi...
Article
Full-text available
Database transformations provide a unifying framework for database queries and updates. Recently, it was shown that non-deterministic database transformations can be captured exactly by a variant of ASMs, the so-called Database Abstract StateMachines (DB-ASMs). In this article we present a logic for DB-ASMs, extending the logic of Nanchen and St\"a...
Article
A behavioural theory consists of machine-independent postulates characterizing a particular class of algorithms or systems, an abstract machine model that provably satisfies these postulates, and a rigorous proof that any algorithm or system stipulated by the postulates is captured by the abstract machine model. The class of interest in this articl...
Conference Paper
We review several semantic restrictions to second-order quantification proposed in the literature. Our focus is on the expressibility and complexity over finite models, or equivalently relational databases, of the second-order logics obtained under those semantic restrictions. We also provide new insights and results in this topic.
Conference Paper
Keys are fundamental for database management, independently of the particular data model used. In particular, several notions of XML keys have been proposed over the last decade, and their expressiveness and computational properties have been analyzed in theory. In practice, however, expressive notions of XML keys with good reasoning capabilities h...

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