Enrico Nardelli | "Tor Vergata" University of Rome (original) (raw)
Papers by Enrico Nardelli
Lecture Notes in Computer Science, 2003
The performance of a database management system (DBMS) is fundamentally dependent on the access m... more The performance of a database management system (DBMS) is fundamentally dependent on the access methods and query processing techniques available to the system. Traditionally, relational DBMSs have relied on well-known access methods, such as the ubiquitous B + -tree, hashing with chaining, and, in some cases, linear hashing . Object-oriented and object-relational systems have also adopted these structures to a great extend.
Lecture Notes in Computer Science, 2001
SDDSs (Scalable Distributed Data Structures) are access methods specifically designed to satisfy ... more SDDSs (Scalable Distributed Data Structures) are access methods specifically designed to satisfy the high performance requirements of a distributed computing environment made up by a collection of computers connected through a high speed network. In this paper we present and discuss performances of ADST, a new order preserving SDDS with a worst-case constant cost for exact-search queries, a worst-case logarithmic cost for update queries, and an optimal worst-case cost for range search queries of O(k) messages, where k is the number of servers covering the query range. Moreover, our structure has an amortized almost constant cost for any single-key query. Finally, our scheme can be easily generalized to manage k-dimensional points, while maintaining the same costs of the 1-dimensional case. We report experimental comparisons between ADST and its direct competitors (i.e., LH*, DRT, and RP*) where it is shown that ADST behaves clearly better. Furthermore we show how our basic technique can be combined with recent proposals for ensuring high-availability to an SDDS. Therefore our solution is very attractive for network servers requiring both a fast response time and a high reliability.
Lecture Notes in Computer Science, 2001
Scalable Distributed Data Structures (SDDS) are access methods specifically designed to satisfy t... more Scalable Distributed Data Structures (SDDS) are access methods specifically designed to satisfy the high performance requirements of a distributed computing environment made up by a collection of computers connected through a high speed network. In this paper we propose an order preserving SDDS with a worst-case constant cost for exact-search queries and a worst-case logarithmic cost for update queries. Since our technique preserves the ordering between keys, it is also able to answer to range search queries with an optimal worst-case cost of O(k) messages, where k is the number of servers covering the query range. Moreover, our structure has an amortized almost constant cost for any single-key query. Hence, our proposal is the first solution combining the advantages of the constant worst-case access cost featured by hashing techniques (e.g. LH*) and of the optimal worst-case cost for range queries featured by order preserving techniques (e.g., RP* and DRT). Furthermore, recent proposals for ensuring high-availability to an SDDS can be easily combined with our basic technique. Therefore our solution is a theoretical achievement potentially attractive for network servers requiring both a fast response time and a high reliability. Finally, our scheme can be easily generalized to manage k-dimensional points, while maintaining the same costs of the 1-dimensional case.
Abstract In network communication systems, frequently messages are routed along a minimum diamete... more Abstract In network communication systems, frequently messages are routed along a minimum diameter spanning tree (MDST) of the network, to minimize the maximum delay in delivering a message. When a transient edge failure occurs, it is important to choose a temporary replacement edge which minimizes the diameter of the new spanning tree. Such an optimal replacement is called the best swap. As a natural extension, the all-best-swaps (ABS) problem is the problem of finding the best swap for every edge of the MDST.
Abstract In this paper we analyze the amortized cost of inserts and exact searches in a DRT*, an ... more Abstract In this paper we analyze the amortized cost of inserts and exact searches in a DRT*, an order preserving scalable distributed data structure able to manage both mono-dimensional and multi-dimensional data.
ABSTRACT The paper describes the certification mark promoted by the Italian Association of Comput... more ABSTRACT The paper describes the certification mark promoted by the Italian Association of Computer Science University Professors (GRIN) for undergraduate and graduate degree programs in Computer Science. The certification process yields a system of comparable and transparent curricula that facilitates student mobility across different Universities.
Abstract We present and discuss a novel architectural approach supporting the integration among l... more Abstract We present and discuss a novel architectural approach supporting the integration among legacy information systems of autonomous organizations. It is based on the use of a data warehouse in a new conceptual role. Namely, we propose to use it during design and implementation of a cooperative information system as a tool supporting the coherence maintenance of the underlying databases and the efficient management of accesses to them.
Abstract Whereas earlier work on spatiotemporal databases generally focused on geometries changin... more Abstract Whereas earlier work on spatiotemporal databases generally focused on geometries changing in discrete steps, the emerging area of moving objects databases supports geometries changing continuously. Two important abstractions are moving point and moving region, modelling objects for which only the time-dependent position, or also the shape and extent are relevant, respectively.
Introduction and summary. We consider planar spatial databases in the topological data model, i.e... more Introduction and summary. We consider planar spatial databases in the topological data model, i.e., databases that consist of a finite number of labeled regions in the real plane. Figure 1 (a) gives an example of such a database showing four labeled regions. Egenhofer and his collaborators, who were among the first to consider this model, have studied the possible topological relationships between regions in the plane and proposed a number of predicates (the so-called 9-intersection model) to express topological properties of pairs of regions (see, e.g., [1]). Later on, the topological data model was investigated further and given a theoretical foundation by Papadimitriou, Segoufin, Suciu, and Vianu [3, 6], who considered first-order languages, built on the predicates of the 9-intersection model, to express topological properties of spatial data (for an overview and a general discussion on topological spatial data and topological queries see also ). In these languages the input databases as well as the variables range over some infinite class of regions.
In an undirected, 2-node connected graph G=(V, E) with positive real edge lengths, the distance b... more In an undirected, 2-node connected graph G=(V, E) with positive real edge lengths, the distance between any two nodes r and s is the length of a shortest path between r and s in G. The removal of a node and its incident edges from G may increase the distance from r to s. A most vital node of a given shortest path from r to s is a node (other than r and s) whose removal from G results in the largest increase of the distance from r to s.
In this paper we consider two new cost measures related to the communication overhead and the spa... more In this paper we consider two new cost measures related to the communication overhead and the space requirements associated to virtual path layouts in ATM networks, that is the edge congestion and the node congestion. Informally, the edge congestion of a given edge e at an incident node u is defined as the number of VPs terminating or starting from e at u, while the node congestion of a node v is defined as the number of VPs having v as an endpoint.
In this paper we describe the overall process of deployment of the Italian Electronic Identity Ca... more In this paper we describe the overall process of deployment of the Italian Electronic Identity Card: the way it is issued, services it is used for, organizations involved in the process, and the Information Technology (IT) infrastructure enabling the effective management of the whole process while ensuring the mandatory security functions.
Methods We present a method for translating a gene network motif to a SC and we show how it overc... more Methods We present a method for translating a gene network motif to a SC and we show how it overcomes the limitations of the method proposed by Shin et Al., by applying it to a number of network motifs. Our method can be used for modeling GRN in an easy and intuitive way by taking advantage of the visual features of SC, and for interactively simulating the execution of the model even in the presence of perturbation by external events.
Identity management systems play a critical role in the field of e-Government and e-Business, as ... more Identity management systems play a critical role in the field of e-Government and e-Business, as they constitute the basic building blocks enabling secure and reliable access to online services. In this chapter, we highlight the main technical and organizational pitfalls of current approaches to identity management which are either based on a centralized architecture or require adoption of common (technological and organizational) standards.
In the delivery of e-government services to citizens it should be clear that the viewpoint cannot... more In the delivery of e-government services to citizens it should be clear that the viewpoint cannot simply be the standard one of client-supplier commonly used to provide services on the Internet. In a modern society it has rather to be the peer-to-peer approach which is typical of democracies, where institutions are equal to citizens in front of the law. But this is not yet a widely accepted standpoint in digital government efforts going on in many advanced countries in the world.
Una delle principali sfide per la comunità accademica è quella della qualità. L'autonomia che è s... more Una delle principali sfide per la comunità accademica è quella della qualità. L'autonomia che è stata data ai singoli Atenei nella specifica dei percorsi di studio espone alla responsabilità di proporre e gestire itinerari formativi di qualità, che sappiano confrontarsi sia con le attese culturali degli studenti, che con le esigenze di un mercato del lavoro sempre più attento ai contenuti e alla solidità delle competenze acquisite dai laureati.
ABSTRACT In this paper we propose and analyze a new meaningful branching sequence to generate ran... more ABSTRACT In this paper we propose and analyze a new meaningful branching sequence to generate random quadtrees representing binary images. In particular, we show that this sequence produces expected distributions of external and intemal nodes much closer to real data than all previous proposed approaches in the literature to model both random binary images and quadtrees. This new model provides a good compromise in representing images belonging to various classes, more or less structured.
Abstract In this paper we describe the architectural solution defined and implemented to ensure s... more Abstract In this paper we describe the architectural solution defined and implemented to ensure secure interoperability among information technology (IT) systems managing personal data registries in Italian municipalities and Ministry of Interior. The architecture features a clear separation between security services, provided at an infrastructure level, and application services, exposed on the Internet as Web services.
Lecture Notes in Computer Science, 2003
The performance of a database management system (DBMS) is fundamentally dependent on the access m... more The performance of a database management system (DBMS) is fundamentally dependent on the access methods and query processing techniques available to the system. Traditionally, relational DBMSs have relied on well-known access methods, such as the ubiquitous B + -tree, hashing with chaining, and, in some cases, linear hashing . Object-oriented and object-relational systems have also adopted these structures to a great extend.
Lecture Notes in Computer Science, 2001
SDDSs (Scalable Distributed Data Structures) are access methods specifically designed to satisfy ... more SDDSs (Scalable Distributed Data Structures) are access methods specifically designed to satisfy the high performance requirements of a distributed computing environment made up by a collection of computers connected through a high speed network. In this paper we present and discuss performances of ADST, a new order preserving SDDS with a worst-case constant cost for exact-search queries, a worst-case logarithmic cost for update queries, and an optimal worst-case cost for range search queries of O(k) messages, where k is the number of servers covering the query range. Moreover, our structure has an amortized almost constant cost for any single-key query. Finally, our scheme can be easily generalized to manage k-dimensional points, while maintaining the same costs of the 1-dimensional case. We report experimental comparisons between ADST and its direct competitors (i.e., LH*, DRT, and RP*) where it is shown that ADST behaves clearly better. Furthermore we show how our basic technique can be combined with recent proposals for ensuring high-availability to an SDDS. Therefore our solution is very attractive for network servers requiring both a fast response time and a high reliability.
Lecture Notes in Computer Science, 2001
Scalable Distributed Data Structures (SDDS) are access methods specifically designed to satisfy t... more Scalable Distributed Data Structures (SDDS) are access methods specifically designed to satisfy the high performance requirements of a distributed computing environment made up by a collection of computers connected through a high speed network. In this paper we propose an order preserving SDDS with a worst-case constant cost for exact-search queries and a worst-case logarithmic cost for update queries. Since our technique preserves the ordering between keys, it is also able to answer to range search queries with an optimal worst-case cost of O(k) messages, where k is the number of servers covering the query range. Moreover, our structure has an amortized almost constant cost for any single-key query. Hence, our proposal is the first solution combining the advantages of the constant worst-case access cost featured by hashing techniques (e.g. LH*) and of the optimal worst-case cost for range queries featured by order preserving techniques (e.g., RP* and DRT). Furthermore, recent proposals for ensuring high-availability to an SDDS can be easily combined with our basic technique. Therefore our solution is a theoretical achievement potentially attractive for network servers requiring both a fast response time and a high reliability. Finally, our scheme can be easily generalized to manage k-dimensional points, while maintaining the same costs of the 1-dimensional case.
Abstract In network communication systems, frequently messages are routed along a minimum diamete... more Abstract In network communication systems, frequently messages are routed along a minimum diameter spanning tree (MDST) of the network, to minimize the maximum delay in delivering a message. When a transient edge failure occurs, it is important to choose a temporary replacement edge which minimizes the diameter of the new spanning tree. Such an optimal replacement is called the best swap. As a natural extension, the all-best-swaps (ABS) problem is the problem of finding the best swap for every edge of the MDST.
Abstract In this paper we analyze the amortized cost of inserts and exact searches in a DRT*, an ... more Abstract In this paper we analyze the amortized cost of inserts and exact searches in a DRT*, an order preserving scalable distributed data structure able to manage both mono-dimensional and multi-dimensional data.
ABSTRACT The paper describes the certification mark promoted by the Italian Association of Comput... more ABSTRACT The paper describes the certification mark promoted by the Italian Association of Computer Science University Professors (GRIN) for undergraduate and graduate degree programs in Computer Science. The certification process yields a system of comparable and transparent curricula that facilitates student mobility across different Universities.
Abstract We present and discuss a novel architectural approach supporting the integration among l... more Abstract We present and discuss a novel architectural approach supporting the integration among legacy information systems of autonomous organizations. It is based on the use of a data warehouse in a new conceptual role. Namely, we propose to use it during design and implementation of a cooperative information system as a tool supporting the coherence maintenance of the underlying databases and the efficient management of accesses to them.
Abstract Whereas earlier work on spatiotemporal databases generally focused on geometries changin... more Abstract Whereas earlier work on spatiotemporal databases generally focused on geometries changing in discrete steps, the emerging area of moving objects databases supports geometries changing continuously. Two important abstractions are moving point and moving region, modelling objects for which only the time-dependent position, or also the shape and extent are relevant, respectively.
Introduction and summary. We consider planar spatial databases in the topological data model, i.e... more Introduction and summary. We consider planar spatial databases in the topological data model, i.e., databases that consist of a finite number of labeled regions in the real plane. Figure 1 (a) gives an example of such a database showing four labeled regions. Egenhofer and his collaborators, who were among the first to consider this model, have studied the possible topological relationships between regions in the plane and proposed a number of predicates (the so-called 9-intersection model) to express topological properties of pairs of regions (see, e.g., [1]). Later on, the topological data model was investigated further and given a theoretical foundation by Papadimitriou, Segoufin, Suciu, and Vianu [3, 6], who considered first-order languages, built on the predicates of the 9-intersection model, to express topological properties of spatial data (for an overview and a general discussion on topological spatial data and topological queries see also ). In these languages the input databases as well as the variables range over some infinite class of regions.
In an undirected, 2-node connected graph G=(V, E) with positive real edge lengths, the distance b... more In an undirected, 2-node connected graph G=(V, E) with positive real edge lengths, the distance between any two nodes r and s is the length of a shortest path between r and s in G. The removal of a node and its incident edges from G may increase the distance from r to s. A most vital node of a given shortest path from r to s is a node (other than r and s) whose removal from G results in the largest increase of the distance from r to s.
In this paper we consider two new cost measures related to the communication overhead and the spa... more In this paper we consider two new cost measures related to the communication overhead and the space requirements associated to virtual path layouts in ATM networks, that is the edge congestion and the node congestion. Informally, the edge congestion of a given edge e at an incident node u is defined as the number of VPs terminating or starting from e at u, while the node congestion of a node v is defined as the number of VPs having v as an endpoint.
In this paper we describe the overall process of deployment of the Italian Electronic Identity Ca... more In this paper we describe the overall process of deployment of the Italian Electronic Identity Card: the way it is issued, services it is used for, organizations involved in the process, and the Information Technology (IT) infrastructure enabling the effective management of the whole process while ensuring the mandatory security functions.
Methods We present a method for translating a gene network motif to a SC and we show how it overc... more Methods We present a method for translating a gene network motif to a SC and we show how it overcomes the limitations of the method proposed by Shin et Al., by applying it to a number of network motifs. Our method can be used for modeling GRN in an easy and intuitive way by taking advantage of the visual features of SC, and for interactively simulating the execution of the model even in the presence of perturbation by external events.
Identity management systems play a critical role in the field of e-Government and e-Business, as ... more Identity management systems play a critical role in the field of e-Government and e-Business, as they constitute the basic building blocks enabling secure and reliable access to online services. In this chapter, we highlight the main technical and organizational pitfalls of current approaches to identity management which are either based on a centralized architecture or require adoption of common (technological and organizational) standards.
In the delivery of e-government services to citizens it should be clear that the viewpoint cannot... more In the delivery of e-government services to citizens it should be clear that the viewpoint cannot simply be the standard one of client-supplier commonly used to provide services on the Internet. In a modern society it has rather to be the peer-to-peer approach which is typical of democracies, where institutions are equal to citizens in front of the law. But this is not yet a widely accepted standpoint in digital government efforts going on in many advanced countries in the world.
Una delle principali sfide per la comunità accademica è quella della qualità. L'autonomia che è s... more Una delle principali sfide per la comunità accademica è quella della qualità. L'autonomia che è stata data ai singoli Atenei nella specifica dei percorsi di studio espone alla responsabilità di proporre e gestire itinerari formativi di qualità, che sappiano confrontarsi sia con le attese culturali degli studenti, che con le esigenze di un mercato del lavoro sempre più attento ai contenuti e alla solidità delle competenze acquisite dai laureati.
ABSTRACT In this paper we propose and analyze a new meaningful branching sequence to generate ran... more ABSTRACT In this paper we propose and analyze a new meaningful branching sequence to generate random quadtrees representing binary images. In particular, we show that this sequence produces expected distributions of external and intemal nodes much closer to real data than all previous proposed approaches in the literature to model both random binary images and quadtrees. This new model provides a good compromise in representing images belonging to various classes, more or less structured.
Abstract In this paper we describe the architectural solution defined and implemented to ensure s... more Abstract In this paper we describe the architectural solution defined and implemented to ensure secure interoperability among information technology (IT) systems managing personal data registries in Italian municipalities and Ministry of Interior. The architecture features a clear separation between security services, provided at an infrastructure level, and application services, exposed on the Internet as Web services.