arXiv subjects

Molham Aref

Publications and source records attributed to Molham Aref.

4 recordsLinked to original sources

arXiv2026

Time to Move on: Querying without Nulls and Bags

SQL is the database community's success story in terms of language design. The key reason for its success is its declarativeness: it gives rise to optimizability, reducing the programmer's burden significantly. However, given the evolving complexity of problems to solve with query languages, our community needs to re-think some of the fundamental early query language design decisions. Our experience in having worked on the design of Rel (a language for end-to-end relational programming) tells us that it is possible to design, implement, and successfully deploy a language based on fully normalized relations. Such relations avoid what Codd called corrupted relations and what we commonly refer to as bags, and the 'harmful' 'billion dollar mistake' that we know as nulls. In the SQL world, it is accepted that bags and nulls are tolerated as an unavoidable evil. We argue that the evil is completely avoidable: reasons offered for justifying bags and nulls evaporate at a closer examination. In addition to debunking them, we also describe opportunities offered by a null-free language with set semantics.

cs.DB↗

arXiv2025

Rel: A Programming Language for Relational Data

From the moment of their inception, languages for relational data have been described as sublanguages embedded in a host programming language. Rel is a new relational language whose key design goal is to go beyond this paradigm with features that allow for programming in the large, making it possible to fully describe end to end application semantics. With the new approach we can model the semantics of entire enterprise applications relationally, which helps significantly reduce architecture complexity and avoid the well-known impedance mismatch problem. This paradigm shift is enabled by 50 years of database research, making it possible to revisit the sublanguage/host language paradigm, starting from the fundamental principles. We present the main features of Rel: those that give it the power to express traditional query language operations and those that are designed to grow the language and allow programming in the large.

cs.DB↗

arXiv2015

Join Processing for Graph Patterns: An Old Dog with New Tricks

Join optimization has been dominated by Selinger-style, pairwise optimizers for decades. But, Selinger-style algorithms are asymptotically suboptimal for applications in graphic analytics. This suboptimality is one of the reasons that many have advocated supplementing relational engines with specialized graph processing engines. Recently, new join algorithms have been discovered that achieve optimal worst-case run times for any join or even so-called beyond worst-case (or instance optimal) run time guarantees for specialized classes of joins. These new algorithms match or improve on those used in specialized graph-processing systems. This paper asks can these new join algorithms allow relational engines to close the performance gap with graph engines? We examine this question for graph-pattern queries or join queries. We find that classical relational databases like Postgres and MonetDB or newer graph databases/stores like Virtuoso and Neo4j may be orders of magnitude slower than these new approaches compared to a fully featured RDBMS, LogicBlox, using these new ideas. Our results demonstrate that an RDBMS with such new algorithms can perform as well as specialized engines like GraphLab -- while retaining a high-level interface. We hope this adds to the ongoing debate of the role of graph accelerators, new graph systems, and relational systems in modern workloads.

cs.DB↗

arXiv2009

Declarative Reconfigurable Trust Management

In recent years, there has been a proliferation of declarative logic-based trust management languages and systems proposed to ease the description, configuration, and enforcement of security policies. These systems have different tradeoffs in expressiveness and complexity, depending on the security constructs (e.g. authentication, delegation, secrecy, etc.) that are supported, and the assumed trust level and scale of the execution environment. In this paper, we present LBTrust, a unified declarative system for reconfigurable trust management, where various security constructs can be customized and composed in a declarative fashion. We present an initial proof-of-concept implementation of LBTrust using LogicBlox, an emerging commercial Datalog-based platform for enterprise software systems. The LogicBlox language enhances Datalog in a variety of ways, including constraints and meta-programming, as well as support for programmer defined constraints which on the meta-model itself ? meta-constraints ? which act to restrict the set of allowable programs. LBTrust utilizes LogicBlox?s meta-programming and meta-constraints to enable customizable cryptographic, partitioning and distribution strategies based on the execution environment. We present uses cases of LBTrust based on three trust management systems (Binder, D1LP, and Secure Network Datalog), and provide a preliminary evaluation of a Binder-based trust management system.

cs.CR↗