In Memoriam: Isabel Cruz

Roberto Tamassia

Isabel Cruz's life and career were prematurely terminated on September 19, 2021 following unexpected complications from a surgery. Her legacy will endure through the impact of her work spanning three and a half decades, and will be carried out by her students, collaborators, and other people whose lives she touched.

Isabel was born and grew up in Lisbon, Portugal. As a child, she was fascinated by reading books about the lives of women who changed the world. In particular, she was inspired by Joan of Arc and Marie Curie. The following quotes from them remained impressed in the mind of young Isabel, and later became part of her work ethos:

"All battles are first won or lost, in the mind.'' (Joan of Arc)

"Have no fear of perfection; you’ll never reach it.'' (Marie Curie)

Isabel's early interest in science found a supportive environment in a family with a father engineer and a mother mathematician who believed gender should not constrain career choices. After completing her undergraduate degree and a master's in electrical engineering in Portugal, she continued her graduate studies at the University of Toronto, where she earned a PhD in Computer Science advised by Alberto Mendelzon.

After a postdoc at Brown University, advised by Paris Kanellakis, she began her faculty career and found a supportive academic home at the University of Illinois Chicago (UIC), which she joined as tenured Associate Professor of Computer Science in 2001. When she was promoted to Professor and later recognized as Distinguished Professor, she was each time the first woman of her department to advance to such ranks. Other recognitions for her work include Fellow of the American Association for the Advancement of Science (AAAS), UIC Distinguished Researcher of the Year in the Natural Sciences and Engineering, University of Illinois Scholar, Great Cities Institute Scholar (twice), and recipient of an NSF CAREER award.

Work by Isabel in the 80s and early 90s pioneered innovations in query languages for data management systems, introducing a powerful framework for the visual specifications of queries that considerably extended the expressiveness of SQL and other textual query languages being used at the time. Her contributions to the G and G+ graphical query languages and her singly-authored paper on the DOODLE visual language gave formal foundation and momentum to a significant development in database research that led to the adoption of recursive queries in a milestone SQL revision.

Building on her visual queries work, Isabel developed efficient constraint-based systems for visual querying and information visualization based on formal logic theory, with applications to graph drawing, algorithm animation, and multimedia systems.

As research on graph databases is gaining major momentum, Isabel's groundbreaking work on graph queries from three decades ago continues to be steadily cited.

Referring to Isabel's SIGMOD 1987 seminal paper on query languages for graphs, a review article on knowledge graphs by Claudio Gutierrez and Juan F. Sequeda in Comm. ACM (2021) states:

"This work would become the basis of modern graph query languages.''

Remarkably, the above influential paper by Isabel is her very first publication, written while she was a graduate student.

Over the past two decades, Isabel shifted her research focus to data integration, a fundamental challenge in data management and analytics. She became especially interested in the problem of discovering matchings (associations) between entities and concepts from diverse and heterogeneous data sources. Her motivation for this research pursuit was increasingly driven by a quest for data science to become an agent for social good, envisioning the use of data integration as a key scientific enabler of novel solutions for social and and humanitarian causes.

Leading interdisciplinary teams of researchers, she pursued research projects on socially compelling applications such as geospatial data integration and visualization for sustainable smart cities, predictive analytics for malaria elimination, managing food waste to assist food-insecure communities, analyzing the impact of public school closings on student achievement, and sentiment analysis of Covid-19 impact on campus communities from social media. In support of this line of work, she was able to obtain funding by prominent agencies and foundations that seldom support computer scientists, including the National Institutes of Health (NIH), the Bill and Melinda Gates Foundation, and the Bloomberg Philanthropies.

A foundational contribution by Isabel to data integration is a comprehensive framework for matching ontologies, which formally represent bodies of knowledge via concepts and relationships between them. Her ground-breaking approach to ontology matching incorporates novel methods for assessing matching quality, combining matching algorithms, visualizing analytics results, and achieving high performance on real-world datasets. The two ontology matching systems that emerged from this work, AgreementMaker and AgreementMaker Light, are considered best-in-class and have earned accolades by consistently raking as top performers in the Ontology Evaluation Alignment Initiative, where the leading matching systems compete annually.

The ACM SIGSPATIAL (Special Interest Group on Spatial Information) community was especially dear to Isabel as it embodies the interdisciplinary character and practical relevance that characterize much of Isabel's work. Her research contributions in this field include proximity queries in mobile objects databases, aligning land use ontologies, location aware access control systems, mapping underground infrastructure, range query methods that leverage semantic information, and a system for visual analytics of geospatial and temporal data.

Exceptionally devoted to professional service, Isabel maintained a high level of participation in program committees throughout her career with steadfast commitment to contributing her knowledge and wisdom to the peer review of articles. The section of her CV listing her program committee memberships is ten pages long, with an additional full page listing her program committee chair roles!

As Founding Editor of the ACM SIGMOD Digital Symposium Collection (DiSC) and Associate Information Director of ACM SIGMOD (1998-2002), Isabel led early efforts by the ACM in the 1990s to make available research articles in digital form.

Isabel was a founding member of ACM SIGSPATIAL and was closely involved with its flagship conference, the ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems (GIS) for over two decades, serving as program committee co-chair in 2004, general co-chair in 2011 and 2012, plus numerous times as as senior or regular program committee member. Isabel also played an important role in the semantic web research community as a founding member of the International Semantic Web Conference (ISWC). Today both GIS and ISWC are vibrant events with strong academic and industry participation from all over the world.

Isabel's university service was also remarkable. Since she assumed the role of faculty search committee chair two years after joining UIC, she envisioned and successfully advocated for a strategic expansion of the CS department into the area of computer security, and significantly contributed to its effective execution. She also served in high-profile service roles at the university level, including Senator, Dean of Engineering Search Committee member (twice), College of Engineering Executive Committee member, and Provost’s Sustainability Strategic Thinking Advisory Committee member.

Throughout her faculty career, Isabel introduced new courses on emerging topics at the graduate and undergraduate level, including information visualization, web technologies, information retrieval, data science, semantic web, and knowledge graphs. She also enjoyed teaching courses on core subjects such as algorithms, data structures, data management, and programming languages.

In advising, Isabel cared about both the professional growth and personal well-being of her students. She enjoyed long brainstorming sessions with them, often meeting them in the lab rather than in her office. She always had positive words of praise for their accomplishments and gentle words of support when they struggled. Keenly aware of the challenges women encounter in STEM, she served as a mentor and role model for many women, candidly sharing her personal experience and offering encouragement and strategic career advice.

Windblown, New Hampshire

Wailea, Maui, Hawaii

In her personal life, Isabel enjoyed running, cross-country skying, and stand-up paddleboarding, yet also listening to classical music, watching sunsets, and relaxing at the beach. In her own words,

"I enjoy being active (or passive) in beautiful places.'' (Isabel Cruz)

Wailea, Maui, Hawaii

Isabel loved very much her mother, father, and brother, whom she called daily and visited frequently in Portugal during the holidays and on the birthdays of her brother and her mother (same day as hers). She was especially close to her brother Manuel, with whom she shared a keen artistic sense and a passion for classical music.

In the spring of 1992, Roberto Tamassia (the author of this article) was in Rome on sabbatical leave from Brown University. As Isabel had traveled there to attend a conference, a common friend, Tiziana Catarci, introduced them. When Isabel mentioned she was completing her PhD and was going to do a postdoc at Brown, Roberto thought she must have been a gifted child given her youthful appearance. Isabel's and Roberto's love story began in the snowy winter of 1993 in Providence and continued for almost three decades until Isabel's death. They shared love for their parents and younger brothers, a Catholic upbringing, ambition, hard work, and quest for perfection as they had ventured to a new country in pursuit of their careers.

Isabel and Roberto quickly became frequent global travelers to attend conferences, give talks, visit family in Portugal and Italy, and take vacations in exotic places. Their flying intensified once Isabel started working in Chicago as they spent as much time as possible together. Before the Covid-19 pandemic, they each flew over 120,000 miles per year, most of which together, so they used to say that their home was the plane. As travel was a significant part of their lives, they made it pleasant by mastering the art of airline upgrades and becoming regulars at five-star hotels and resorts.

Isabel was gifted in singing and drawing but never found the time to pursue these talents. She loved nature, from the calm waters of Wailea in Maui, to the fierce waves of the Atlantic coast of Portugal, to the majestic mountains surrounding Sundance, Utah. The smell of beautiful roses and lilies, the sight of colorful cardinals and blue jays, and encounters with friendly dogs were cherished moments of happiness for her.

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