Increased interactivity and improvements to the GigaScience database, GigaDB

Abstract With a large increase in the volume and type of data archived in GigaScience Database (GigaDB) since its launch in 2011, we have studied the metrics and user patterns to assess the important aspects needed to best suit current and future use. This has led to new front-end developments and enhanced interactivity and functionality that greatly improve user experience. In this article, we present an overview of the current practices including the Biocurational role of the GigaDB staff, the broad usage metrics of GigaDB datasets and an update on how the GigaDB platform has been overhauled and enhanced to improve the stability and functionality of the codebase. Finally, we report on future directions for the GigaDB resource.


Introduction
There is growing awareness of the societal and technical challenges surrounding reproducibility and rigor in experimental science. The inability of one scientist to reproduce another's work may be largely attributed to the actual artifacts that support the research findings (the data and methods) are largely inaccessible. GigaScience (http://GigaScienceJournal.com) is a journal trying to address this by focusing on reproducibility and reusability when assessing manuscripts rather than subjective impact. Further, we provide citation credit for data to reward and promote the release of large-scale research data for downstream reuse. With data release and credit as a major aim, it is essential that the journal has a data publishing infrastructure that ensures the ability to archive and retrieve the myriad and massive data volumes associated with these 'Big Data' publications. GigaScience has developed an associated database, GigaScience DataBase (GigaDB) (1) to accomplish this and to eliminate the largest excuse for not sharing data: their being too large or that the data types too difficult to make available to the community. GigaDB provides the infrastructure that allows a 'Big Data' journal to archive massive multidimensional datasets that are associated with life science and biomedicine studies.
The integration of GigaDB as part of the submission, reviewing and the publishing process ensures transparency and reproducibility of the article. Importantly, GigaDB is more than just a file server for supplemental files; the datasets are curated by GigaDB staff to ensure the data and metadata are properly curated and organized, and that any links are correct. This assures everything is complete and sufficient for purpose. As a journal with a focus on reproducibility and reuseability of data, peer reviewers have access to all of the supporting data, and the curation process is closely tied to the manuscript review process to ensure timely publication in conjunction with the manuscript, something currently missing from most journal review processes. Trained curators assess the manuscript and data provided by the authors and advise on missing or unclear data and also provide advice on more suitable data formats and recognized standards, such as Genomic Standards Consortium (GSC) (2). Where possible and appropriate, authors are encouraged, and sometimes mandated, to submit data to the relevant public repositories hosted by centers of excellence in the relevant fields, e.g. the European Nucleotide Archive (https://www.ebi.ac.uk/ena/) and the Sequence Read Archive (SRA) (https://www.ncbi.nlm.nih. gov/sra).
Datasets hosted in GigaDB are defined as a group of files (e.g. sequencing data, analyses, imaging files, software programs and scripts) and metadata (e.g. sample attributes, protocols and file attributes) that are related to, and support, a specific article or study. Through our membership of DataCite (https://www.datacite.org/), each dataset in GigaDB is assigned a digital object identifier (DOI) that should be used as a standard citation for future use in other articles by researchers who use these data. The dataset DOI ensures that the title, creators/authors and additional minimal information are recorded and made permanently available. In addition to fulfilling the requirements of DOI publication, we also aim to maintain the usefulness of the data by allowing minor revisions to be made by tracking all changes in a history log on the dataset page. If major changes are required, a new DOI can be issued and users redirected to the new version with a notice offering to display the original version, which will always be maintained.
GigaDB is managed using the FAIR Principles for scientific data management and stewardship, which state that research data should be Findable, Accessible, Interoperable and Reusable (3). GigaDB datasets are also citable, transforming FAIR into FORCE (FAIR, Open, Research-Object based and Citable Ecosystem) (4).

Datasets, data types and data curation
GigaDB hosts datasets from across the life and biomedical sciences and there are currently 20 different dataset types ( Figure 1). In liaison with the authors of the manuscript, GigaDB staff procure all available files and metadata and assist the authors throughout the submission process including assigning dataset types to each dataset. Importantly, multiple types can be ascribed to a single dataset, such that a study that includes both a draft genome assembly (DNA) and aligned transcriptome reads (RNA) would be tagged as both 'Genomic' and 'Transcriptomic'. The GigaDB website utilizes these tags and allows users of the web interface to filter datasets based on these categories.
As discussed in detail (5) the need to balance the carrot and stick approach to publishing large datasets is still apparent, and many authors are not yet experienced in this matter. GigaDB staff are experienced professional curators, who can provide personalized assistance and guidance to authors where required, and initially authors are provided with guidelines that can be used as a checklist to ensure that all the necessary files associated with the manuscript are submitted (Table 1). We believe these checklists will prove to be especially helpful for authors who are submitting data to GigaDB for the first time. Furthermore, these checklists can easily be extended to accommodate new dataset types as GigaScience continues to expand its breadth of coverage within the life sciences. Indeed, part of the challenge at GigaDB is remaining cutting edge in the ability to identify the appropriate file types that should be submitted with each new dataset type. Finally, by having the data available for the peer review process, the referees are also able to provide input on which data are important and if there are additional data still missing.
Where appropriate, GigaDB staff ensure that data are submitted to the public repository, and that those data are made publicly available at the time of manuscript publication. This is an exceptionally important part of the data publishing process that is often missed at other journals as it is not embedded as part of the publishing process. The biocuration team include multiple steps in the submission to publication process that remind authors to submit, for example, sequence data to the SRA and then to remind them to have these publicly released prior to publication of the GigaScience manuscript that references these datasets.
Checking the data types and availability provides an invaluable opportunity to review the sample attributes associated with the biological samples submitted to the data repositories. Submitting authors are encouraged to ensure that the sample attributes they provide are GSC compliant and assisted by GigaDB curators in the use of ontologies and the correct use of the myriad of possible sample attribute terms. The provision of comprehensive sample metadata ensures the best possible reach of data published in GigaDB and helps the end user find and filter relevant datasets. In addition, interconnectivity of data, and the inclusion of links to external repositories that are referred to in the manuscript, is encouraged. These external  GigaDB has additionally installed the community annotation layer 'Hypothes.is' within the GigaDB codebase. This allows community-based comments/feedback to be annotated on datasets within each dataset page. We feel that there are key advantages to this overlay approach over the traditional 'add comments' section at the bottom of a web page as it facilitates adding specific comments and/or tags to the relevant point in the webpage. Hypothes.is also allows registered users to set up groups so that they can have private discussions about a webpage directly on that page, these comments can later be made public if desired.

Analytics and metrics on use
Launched in 2011, and now with over 550 datasets, GigaDB is able to generate some interesting usage analytics. This data complements the previously published usage analysis of individual high-profile datasets such as the Rice 3K data (6) and the genome of the deadly 2011 German E. coli outbreak (7).
While we are indexed by the Web of Science Data Citation Index (https://clarivate.com/products/web-ofscience/web-science-form/data-citation-index/), Datamed. org (http://datamed.org), and other services that index our DataCite metadata, it is difficult to collect and present accurate data citation statistics. While CrossRef and DataCite event data does collect data citations in an open format, they only collect data citations correctly cited in the reference sections of indexed publications. This misses any misformatted citations and any links to the datasets referred to in the body of the paper, which from our experience has been the majority of usage. While the FORCE11 Data Citation Principles (which we endorsed at its launch) has promoted the correct practice of citing datasets by DOI in the reference section (4) we have been publishing data since before this was published; and despite our efforts in promotion (8) this is still not the norm for other publishers.
We are able to make use of the services provided by Europe PMC (https://europepmc.org/) and Google Scholar (https://scholar.google.com/) to track the number of 'citations' (or hits) of GigaDB DOIs in published articles.
Google Scholar has a broad reach and (unlike Europe PMC) generally includes articles on the periphery of scientific publishing, including some scientific blog posts, patents and news articles; hence in general the number of citations being returned by Google Scholar is higher than that returned by Europe PMC. In fact, every dataset published in GigaDB contains links to the search results from both Europe PMC and Google Scholar, which allows users to get up to date citations from those sources.
By searching for the unique DOI prefix '10.5524/' we have polled Google Scholar and Europe PMC search tools by year, to determine the overall number of appearances of GigaDB datasets in the scientific literature ( Figure 2). As the trend lines indicate there has been a steady increase in citation of GigaDB datasets over time.
As described above, the FORCE11 Data Citation Principles are not always adhered to, so looking for dataset citations in the literature tells only part of the story. We would miss those instances where authors simply acknowledge a dataset by name within the text, and of course there are likely to be other instances of reuses of datasets that have yet to reach publication. In an attempt to identify more 'of the moment' metrics, GigaDB collects other metrics of data usage, including web browser, data access and file download statistics, as an additional proxy to the official data (re)use metrics.
Google Analytics (https://analytics.google.com/) is a web analytics service offered by Google that tracks and reports website traffic. GigaDB first started using this service in May 2013, and the chart below (Figure 3) shows the type of information that can be obtained using this mechanism: in this case, the count of unique visitors per month over the 5-year period 2013-2018.
In the period 31st January 2017 to 7th May 2018 we analyzed file transfer protocol (FTP) server logs to see how much data was being downloaded. The chart (Figure 4) shows the number of unique internet protocol (IP) addresses (used as a proxy for individual users) successfully downloading one or more files from any given dataset during that period. On average at least one file was downloaded from each dataset by 45 different users during the 15-month period monitored. Some datasets had 10 times that number e.g. 100064 (9) was downloaded by 497 unique IPs. The long tail on the chart demonstrates that there are a number of datasets that were downloaded only a handful of times.
The FTP log file also records the size of files that are being downloaded, and using those data it is possible to see an increase in data download volume over the period analyzed ( Figure 5).
GigaDB have recently been made aware of the 'Code of practice for research data usage metrics release 1' (10) that will bring some cohesion to this area, and we fully intend to adhere to the guidelines where possible and participate in the future developments of those guidelines.

Keeping up appearances: new GigaDB web-based functionalities
Since the last major update in 2014, the GigaDB interface has received an overhaul to provide a more user-friendly dataset page with greater flexibility. On the dataset page, we still maintain the functionality of being able to link to related GigaDB datasets through use of 'IsPartOf ' and 'HasPart' relationships. However, we now provide multiple tabs as a means of navigating between the GigaDB sample, files, funding and history information ( Figure 6). The inclusion of multiple tabs ensures easy navigation and additionally allows novel views of the data. To illustrate with one example, micro computed tomography (microCT) data files can be inspected as a file list as before, but example data files can now also be explored in the context of an interactive 3D viewer (Figure 7). Behind-thescenes, the GigaDB team are generating surface reconstructions for recently submitted microCT datasets and making these publicly available using SketchFab (https:// sketchfab.com/GigaDB). The newly launched GigaDB website is able to embed these outside resources within an additional tab on the GigaDB page, and this allows alternative views of the data. Other embeddable media that we currently support are JBrowse (Genome browser), Code Ocean  Under the hood: improvements to the code, testing and deployment The hypertext preprocessor (PHP) source code for GigaDB is freely available on GitHub (see availability of supporting source code and requirements). Requests for new functionality and notification of software bugs can also be raised as issues on the GigaDB GitHub repository webpage. GigaDB was initially created with PHP 5 using version 1 of the object-oriented, model-view-controller Yii framework but recent development work has upgraded it to use PHP 7 and Yii 2.0. The GigaDB source code has also been refactored to reduce its complexity. In addition, a behaviordriven development process is now coupled with test-driven development and unit testing techniques for developing the GigaDB application. We have also adopted continuous integration and continuous deployment approaches to automate checking of the GigaDB source code so that the application is not broken and that new functionality is made available in a timely manner on the web site, respectively.

Future directions
Embeddable media. While we already have in place the Web3D application SketchFab, which allows interactive views of 3D images, we will also provide a section viewer that allows the end user to choose a 2D section through a 3D image and pan-and-zoom on the selected image. The focus here is on developing web tools that allow researchers to preview large data prior to data download. With minor modification, the section viewer can additionally accommodate time series data, such as time-lapse video microscopy data and camera-trap images, examples of which already exist in GigaDB.

Submission tools.
To ensure more rapid submission of data associated with GigaScience articles, GigaDB is developing a new version of the GigaDB submission wizard. This webbased interface allows authors to submit a new dataset, directly linked to their manuscript submission, online using web-based forms. The aforementioned checklists of data types associated with datasets categories will be integrated into the wizard to facilitate the process. These developments are underway with the intention to release in mid 2019.

Conclusions
GigaDB have continued to develop its resources further enabling the open sharing of scientific data. The overhaul of the underlying codebase will ensure that developments can continue in a timely manner allowing new and proofof-concept ideas to be deployed in GigaDB.
The collection of a variety of metrics has allowed monitoring of growth over the recent past and moving forward will provide a solid platform to provide users with vital feedback about the use and citation of their data.
The aesthetic changes to the appearance of the website have enabled the inclusion of widgets which in turn allows for a greater versatility. As always, user feedback is encouraged either by direct interaction with the GigaScience and GigaDB staff or via the various online communications.