Showing posts with label linked data. Show all posts
Showing posts with label linked data. Show all posts

Oct 2, 2013

About research objects

Notes from the article by Bechhofer, Buchan, De Roure, Missier, Ainsworth et al. "Why linked data is not enough", Future Generation Computer Systems, 2011, (pdf).

Scientific research is increasingly digital and collaborative, therefore a new framework is needed that would facilitate the reuse and exchange of digital knowledge. Simply publishing data fails to reflect the research methodology and respect the rights and reputation of the researcher.

The concept of Research Objects (ROs) as semantically rich aggregations of resources can serve as a cornerstone of such new framework. ROs would include research questions, hypotheses, abstracts, organisational context (e.g., ethical and governance approvals, investigators, etc.), study design, methods (workflows, scripts, services, software packages. etc.), data, results, answers (e.g., publications, slides, DOIs), etc. The authors argue that this approach is better than linked data, but later they acknowledge that linked data works fine, it just needs to be revised and extended.

Important assumptions in the paper:

  • ROs work well in the context of e-Laboratories - environments that are mostly based on automated management systems and execution of in silico experiments
  • Reproducible research is ultimately possible in any domain and always desirable.
  • All elements of scientific research can be made explicit and encoded in a machine-readable way, if not now, then in the future.

Terms that refer to different ways of reusability:

  • Reusable - reuse as a whole or single entity.
  • Repurposeable - reuse as parts, e.g., taking an RO and substituting alternative services or data for those used in the study.
  • Repeatable - repeat the study, perhaps years later.
  • Reproducible - reproduce or replicate a result (start with the same inputs and methods and see if a prior result can be confirmed).
  • Replayable - automated studies can be replayed rather than executed again.
  • Referenceable - citataions for ROs.
  • Revealable - audit the steps performed in the research in order to be convinced of the validity of results.
  • Respectful - credit and attribution.

The authors describe several environments that try to implement aggregation of resources into ROs approach.

  • myExperiment Virtual Research Environment relies on the notion of "packs", collections of items that can be shared as a single entity.
  • Systems Biology of Microorganisms (SysMO) project has a web plaform SysMO-DB and a catalog SysmoSEEK. It relies on a JERM (Just Enough Results Model), which is based on the ISA (Investigation/Study/Assay) format. Another approach to support ROs within the systems biology community is SBRML (Systems Biology Results Markup Language). Most of the experiments in this domain are wet lab experiments, so traceability and referenceability are more relevant than repeatability and replayability.
  • MethodBox is part of the Obesity e-Lab, that allows researchers to "shop for variables" from studies related to obesity in the UK. The paper doesn't describe what method is used to support RO aggregations.

Packs in myExperiment is the most advanced implementation of the idea of ROs and, ironically, it's based on linked data: "Work in myExperiment makes use of the OAI-ORE vocabulary and model in order to deliver ROs in a Linked Data friendly way" (p. 10).

OAI-ORE defines standards for the description and exchange of aggregations of Web resources. It is agnostic to relationship types, so it needs to be extended. The authors propose the following extensions: the Research Objects Upper Model (ROUM) and the Research Object Domain Schemas (RODS). ROUM provides basic vocabulary to describe general properties of RO, such as the basic lifecycle states. RODS provide domain specific vocabulary. Not much details are provided about these two extensions.

Rather than arguing that linked data is not enough, it seems that the paper argues that current implementations of linked data in packaging scientific results needs to be revised to explicitly include the structure of aggregations. The purpose of articulating structure in a machine-readable way is to create an environment where every component of research (including hypotheses, methods, data and results) can be re-enacted. A more obvious and important conclusion from the discussion about ROs is that a) we need to keep encouraging exchange and sharing of research in ways that are more transparent; b) there is still a shortage of platforms to do that. MyExperiment is a nice example, but it's still domain and platform-specific.

The approach described in this paper is quite forward-looking. It is a call for rather radical changes in scientific practices. I wonder how many labs have automated experiment management environments where all datasets, workflows, scripts and results can be connected and reconstructed without much back-channeling. Another question is how much effort it takes to create ROs in a way that would make science fully "re-enactable". We probably won't be able to do that with legacy data.

May 30, 2013

Notes on RDF/Linked data

A few clarifying points for and against linked data / RDF from a couple of interesting resources.

Big Data journal published an article What Do RDF and SPARQL bring to Big Data Projects?. The article provides a concise yet very clear overview of RDF - a standard to represent structured and semi-structured data, based on triples and globally unique IDs. Unique IDs look like URLs, but their job is naming (i.e., unambiguous naming), not providing locations. They look like URLs, because this allows domain owners to control the naming conventions.

Benefits of RDF over relational databases:

  • independence from schemas (new classes, properties and relationships can be added easily without the need to modify a schema in advance);
  • easy integration and disintegration of datasets; 
  • shared vocabularies; 
  • efficiency in storing datasets that don't have all the same properties for every instance in a class (similar to NoSQL databases). 

The difference of RDF from other noSQL options is that it comes with a query language standard, SPARQL, which allows you to find the connections between triples in aggregated data. SPARQL can be used to query both RDF and non-RDF data. D2RQ platform, for example, can execute a single SPARQL query across databases stored in different relational database management systems.

The overall conclusion of the article is that RDF offers a more flexible solution for big data, the solution that is based on open standards and therefore is interoperable and expandable.

Another resource, a presentation "RDF: Resource Description Failures and Linked Data Letdowns" by Robert Sanderson (YouTube link and Vimeo link and I wish these great presentations existed in some textual form - it's really hard to work with videos) argues that Semantic Web was a great idea in 2003 and still is a great idea in 2013, but it has serious difficulties and complications to overcome:

  • RDF complicates querying and limits it. Both structure and data are important for queries, but in RDF data is treated as a "second class" citizen, because structure is a new thing and more interesting. So full text search, for example, is difficult. You need to know the structure (triple elements) to query RDF. And that's usually a problem for systems with a developed front end - you can't expect users to know the structure. 
  • Serialization and storage become complicated. RDF graphs have no beginning and end and can be cyclic, but you want to store information without repeating it. Triplestore (RDF storage solution) is a one big lump that has not clear documents or objects. If different users put documents in, they might want to treat their contributions as separate.
  • RDF visualization is hard (as opposed to document visualization), because it focuses on structure. But what about data? Hard to see what's going on, labeling and connections are terrible.
  • RDF/Semantic Web is based on the ultimate goal of creating a single global graph. This "Open World" idea is good in theory as it provides richness of data, its re-use, gradual expansion, etc. But global graphs create several problems, e.g., how to deal with local complexity (when statements are true in one context and not true in another). Local identities are also similarly complex.
  • Linked data do not address well changes over time - a lot of work need to be done.

Good things about RDF: open source, scalable, cross-platform, in use by commercial companies, good for inferences and new knowledge, interfaces are fast developing.