The Software Ontology (SWO)

Our paper on the Software Ontology (SWO) has just been published in the Journal of Biomedical Semantics (JBMS) thematic issue on ontologies. The paper is:


James Malone, Andy Brown, Allyson Lister, Jon Ison, Duncan Hull, Helen Parkinson, and Robert Stevens. The software ontology (swo): a resource for reproducibility in biomedical data analysis, curation and digital preservation. Journal of Biomedical Semantics, 5(1):25, 2014.


There’s also a lot of information about how we went about making the SWO at the SWO blog.


We now have a range of bio-ontologies covering sequences, gene products, their functions, the processes in which they participate, cellular and gross anatomy, to diseases and phenotypes. These are primarily used to describe the entities in the masses of data biology now produces. More recently, there’s been work on describing the investigations by which these data were produced and analysed; the SWO fits into the ontology landscape at this location. The data is just a load of stuff; we detect things in these datasets with some software and the provenance trail of how these entities were detected needs to include the software that was used.


The SWO describes software, the software suites of which it is a part, its inputs and outputs, the tasks it supports, its versions, licencing its interface, and its developers. It doesn’t capture the hardware upon which the software runs, the software’s dependencies, cost of ownership (not the price in lucre, but does it need a lot of sys admin kind of thing), software architecture… (see the paper and blog for more)


The scope of the SWO is thus wide and we could have included a whole lot more than we did; much of the stuff not included is important and useful, but resources are scarce and some of the features, like the hardware, is v hard to represent. One of the major problems in writing an ontology is scope and mission creep – how do we stop modelling the world and spending inordinate amounts of time on pathological edge cases? To help us in this we used some Agile techniques in producing the SWO. Perhaps the most useful was the “planning poker” and “buy a feature” games we played. In the SWO project we used a bunch of stakeholders to help us out and the use of these techniques in the SWO went something like this:


  1. We did the usual thing of asking for competency questions (which play the role of user stories); clustering them and drawing out a set of features that needed to be modelled.
  2. For the planning poker, we asked people to estimate the effort needed to represent the feature on a numeric scale. Here the trick is that everyone has cards with notional costs written upon them. All cards are held up simultaneously to prevent bias from the first to reveal his or her card. Discussion ensues and a consensus effort for the ontological feature is decided upon.
  3. We then did the same thing for choosing a feature. Depending on the values for effort an amount of “money” is calculated and distributed evenly amongst the stakeholders; there is not enough money to buy everything. Each feature has a cost and each stakeholder can spend his or her money on the features he or she thinks most important. negotiating and so on takes place and features to be modelled are either bought or not bought.

This actually worked well and produced a list of prioritised SWO features. We didn’t do it often enough, as priorities and cost estimations change, but features to be modelled could be seen to be changed on one iteration of the planning. In the SWO we think this technique struck a good balance between what was needed and what was achieveable.


We also needed to add content for these features to the SWO. In the first round this was driven by what our customers needed – this was largely, but not exclusively, the EBI’s Gene Expression Atlas. Later on, we’ve been a bit more systematic about what to put into the SWO. Using a named entity recogniser for bioinformatics software and databases (BioNERDS) we’ve done a survey of all PMC for mentions of said bioinformatics databases and software. We pulled out the top 50 of these software mentions and we’re slowly ploughing our way through those (I’ve put this list at the end of this Blog).


The paper itself is one in the JBMS thematic series on ontologies; it does for ontologies what the NAR annual database issue does – describes, in this case, ontologies, their state of play and what updates have happened. This is what the SWO paper does. It has the motivation – we need to know how our data were produced and analysed and software plays a crucial role in this analysis. The paper describes what features were bought by our stakeholders, how we axiomatised descriptions of these software features and outlines some of the more tricky modelling issues. My two favourite tricky bits were:


  1. Versions of software. The vast variety of versioning schemes is horrid to represent; we did it with individuals of the class “version name”representing a version for a given bit of software. These versions are linked to preceding and succeeding versions to support the obvious queries. It’s not beautiful, but works well enough.
  2. Licences for software. Again, this has to support the variety of the multitude of licences,but the interesting thing here is to be able to infer that, for instance, a bit of software is open source – the paper describes the axiom pattern to do this trick.



The paper also describes the SWO’s merger with EDAM, which has brought a lot of content into the SWO. The SWO is being used, and not just by the EBI (the paper has some examples) and will continue to grow. The SWO represents a complex field of human developed artefacts. In doing so the SWO team has very much taken a pragmatic approach in its representation. The SWO is already quite complex, but we have tried to avoid being too baroque.


Here’s the top 50 as produced by BioNERDS (it’s actually 49 and there’s a couple of glitches in this data, but it’s good enough)










Tree View


UCSC Genome Browser






































Microarray Suite





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