Semantic Search in Solar-Terrestrial Sciences

The interdisciplinary research and application fields of solar, solar-terrestrial and space physics encompasses a wide variety of physical and chemical phenomena. And increasingly there is a tremendous need for cross-disciplinary collaboration very often underpinned by the ability to find appropriate data and information resources, using them, and sharing outputs. On the provider side, there is a strong need to have the data they produce found and used by many stakeholder groups, i.e. not just researchers. With such diverse areas of study, and emphasis on multi-disciplinarity, the challenges presented in finding appropriate data sources in these solar-terrestrial studies mimic the challenges that emerge out of any almost any interdisciplinary project, especially in terms of the computer science, informatics, and information technology needed to address key data management capabilities, e.g. data discovery/ dissemination. This contribution addresses some specific approaches to the “search problem” in solar-terrestrial sciences. i.e. the search for data and related resources using semantics that have been undertaken over the last ~15 years. Back then the task seemed straightforward. Extracted metadata from mostly individual files was organized into catalogs and made available via Web. However, the homonym problem quickly appeared, as did confusion of what metadata meant what, and where should they reside in the catalog and the interface? At the heart of this combination of multiple disciplines, heterogeneous data, and jargon was that almost no one had used science-terminology-based use cases for exploring and formalizing semantics. Semantics potentially allowed a return to the “science query”, or that was the vision in the early 2000s. Along the way, a process for determining what semantics were required and how could they be implemented, or how should the search infrastructure be modified, was developed. Herein we recap key elements of the progress using semantics for search drawing from two projects: the Virtual Solar-Terrestrial Observatory (VSTO) that became a production, interdisciplinary virtual observatory covering solar and solar-terrestrial physics resources in two primary communities. The particular semantic Web methods and technologies that were used to design, develop and deploy VSTO are presented and discussed. As VSTO evolved, we added additional capabilities based on use cases and demonstrated measureable benefits to the intended and unintended users. In regard to domain semantics for VSTO (and later projects), an extensible, reusable ontology for solar-terrestrial physics was a key output. As VSTO was underway, other projects beyond VSTO's domain were providing clarity as to where different levels of semantics are needed in the architecting of platforms for collaborative research, built upon semantic data frameworks. Thus, the Semantic eScience Framework (SeSF) project was conceived. SeSF aimed at identifying what needed to be in a core framework, i.e. domain independent, so that domain dependencies could be plugged in, and applications deployed. One of the key applications (and still is) is search. The evolution of semantic search via faceted browsing into a cohesive user environment had implication for ontology and interface (widget) developments. Across these two projects, plus ~6 others, many lessons were learned. The ones relevant to semantic search are presented in this contribution. Two important ones were: the balance between expressivity, implementability and maintainability/extensibility of the semantics, i.e. between the level and depth of knowledge representation and what the current and evolving software and tools could support. Secondly, on the use of semantics demanded a similar balance choice among query, inference and rules. The relative combinations were based on the particular stage and iteration of the methodology. Since the evolution of search using semantics is still evolving, musings on current and future development are presented at the end.