arXiv subjects

Miguel E. Coimbra

Publications and source records attributed to Miguel E. Coimbra.

7 recordsLinked to original sources

arXiv2026

Survey: On the Landscape of Graph Databases

Graph databases have become essential tools for managing complex and interconnected data, which is common in areas like social networks, bioinformatics, and recommendation systems. Unlike traditional relational databases, graph databases offer a more natural way to model and query intricate relationships, making them particularly effective for applications that demand flexibility and efficiency in handling interconnected data. Despite their increasing use, graph databases face notable challenges. One significant issue is the irregular nature of graph data, often marked by structural sparsity, such as in its adjacency matrix representation, which can lead to inefficiencies in data read and write operations. Other obstacles include the high computational demands of traversal-based queries, especially within large-scale networks, and complexities in managing transactions in distributed graph environments. Additionally, the reliance on traditional centralized architectures limits the scalability of Online Transaction Processing (OLTP), creating bottlenecks due to contention, CPU overhead, and network bandwidth constraints. This paper presents a thorough survey of graph databases. It begins by examining property models, query languages, and storage architectures, outlining the foundational aspects that users and developers typically engage with. Following this, it provides a detailed analysis of recent advancements in graph database technologies, evaluating these in the context of key aspects such as architecture, deployment, usage, and development, which collectively define the capabilities of graph database solutions.

cs.DB↗

arXiv2023

phyloDB: A framework for large-scale phylogenetic analysis

phyloDB is a modular and extensible framework for large-scale phylogenetic analyses, which are essential for understanding epidemics evolution. It relies on the Neo4j graph database for data storage and processing, providing a schema and an API for representing and querying phylogenetic data. Custom algorithms are also supported, allowing to perform heavy computations directly over the data, and to store results in the database. Multiple computation results are stored as multilayer networks, promoting and facilitating comparative analyses, as well as avoiding unnecessary ab initio computations. The experimental evaluation results showcase that phyloDB is efficient and scalable with respect to both API operations and algorithms execution.

cs.DB↗

arXiv2021

An analysis of the graph processing landscape

The value of graph-based big data can be unlocked by exploring the topology and metrics of the networks they represent, and the computational approaches to this exploration take on many forms. The use-case of performing global computations over a graph, it is first ingested into a graph processing system from one of many digital representations. Extracting information from graphs involves processing all their elements globally, and can be done with single-machine systems (with varying approaches to hardware usage), distributed systems (either homogeneous or heterogeneous groups of machines) and systems dedicated to high-performance computing (HPC). We provide an overview of different aspects of the graph processing landscape and describe classes of systems based on a set of dimensions we detail. The dimensions we detail encompass paradigms to express graph processing, different types of systems to use, coordination and communication models in distributed graph processing, partitioning techniques and different definitions related to the potential for a graph to be updated. This survey is aimed at both the experienced software engineer or researcher as well as the newcomer looking for an understanding of the landscape of solutions (and their limitations) for graph processing.

cs.DC↗

arXiv2019

VeilGraph: Streaming Graph Approximations

Graphs are found in a plethora of domains, including online social networks, the World Wide Web and the study of epidemics, to name a few. With the advent of greater volumes of information and the need for continuously updated results under temporal constraints, it is necessary to explore novel approaches that further enable performance improvements. In the scope of stream processing over graphs, we research the trade-offs between result accuracy and the speedup of approximate computation techniques. We see this as a natural path towards these performance improvements. Herein we present \name, through which we conducted our research. We showcase an innovative model for approximate graph processing, implemented in \texttt{Apache Flink}. We analyze our model and evaluate it with the case study of the PageRank algorithm \cite{pageRank}, perhaps the most famous measure of vertex centrality used to rank websites in search engine results. %In light of our model, we discuss the challenges driven by relations between result accuracy and potential performance gains. Our experiments, even when set up for favoring \texttt{Flink} for comparability, show that \name can improve performance up to 3X speedups, while achieving result quality above 95\% when compared to results of the traditional version of PageRank without any summarization or approximation techniques.

cs.DC↗

arXiv2019

On dynamic succinct graph representations

We address the problem of representing dynamic graphs using $k^2$-trees. The $k^2$-tree data structure is one of the succinct data structures proposed for representing static graphs, and binary relations in general. It relies on compact representations of bit vectors. Hence, by relying on compact representations of dynamic bit vectors, we can also represent dynamic graphs. In this paper we follow instead the ideas by Munro {\em et al.}, and we present an alternative implementation for representing dynamic graphs using $k^2$-trees. Our experimental results show that this new implementation is competitive in practice.

cs.DS↗

arXiv2018

Gelly-Scheduling: Distributed Graph Processing for Network Service Placement in Community Networks

Community networks (CNs) have seen an increase in the last fifteen years. Their members contact nodes which operate Internet proxies, web servers, user file storage and video streaming services, to name a few. Detecting communities of nodes with properties (such as co-location) and assessing node eligibility for service placement is thus a key-factor in optimizing the experience of users. We present a novel solution for the problem of service placement as a two-phase approach, based on: 1) community finding using a scalable graph label propagation technique and 2) a decentralized election procedure to address the multi-objective challenge of optimizing service placement in CNs. Herein we: i) highlight the applicability of leader election heuristics which are important for service placement in community networks and scheduler-dependent scenarios; ii) present a parallel and distributed solution designed as a scalable alternative for the problem of service placement, which has mostly seen computational approaches based on centralization and sequential execution.

cs.DC↗

arXiv2017

Study on Resource Efficiency of Distributed Graph Processing

Graphs may be used to represent many different problem domains -- a concrete example is that of detecting communities in social networks, which are represented as graphs. With big data and more sophisticated applications becoming widespread in recent years, graph processing has seen an emergence of requirements pertaining data volume and volatility. This multidisciplinary study presents a review of relevant distributed graph processing systems. Herein they are presented in groups defined by common traits (distributed processing paradigm, type of graph operations, among others), with an overview of each system's strengths and weaknesses. The set of systems is then narrowed down to a set of two, upon which quantitative analysis was performed. For this quantitative comparison of systems, focus was cast on evaluating the performance of algorithms for the problem of detecting communities. To help further understand the evaluations performed, a background is provided on graph clustering.

cs.DC↗