11 Dec 2011 titus   » (Journeyer)

Data Intensive Science, and Workflows

I'm writing this on my way back from Stockholm, where I attended a workshop on the 4th Paradigm. This is the idea (so named by Jim Gray, I gather?) that data-intensive science is a distinct paradigm from the first three paradigms of scientific investigation -- theory, experiment, and simulation. I was invited to attend as a token biologist -- someone in biology who works with large scale data, and thinks about large scale data, but isn't necessarily only devoted to dealing with large scale data.

The workshop was pretty interesting. It was run by Microsoft, who invited me & paid my way out there. The idea was to identify areas of opportunity in which Microsoft could make investments to help out scientists and develop new perspectives on the future of eScience. To do that, we played a game that I'll call the "anchor game", where we divvied up into groups to discuss the blocks to our work that stemmed from algorithms and tools, data, process and workflows, social/organizational aspects. In each group we put together sticky notes with our "complaints" and then ranked them by how big of an anchor they were on us -- "deep" sticky notes held us back more than shallow sticky notes. We then reorganized by discipline, and put together an end-to-end workflow that we hoped in 5 years would be possible, and then finally we looked for short- and medium-term projects that would help get us there.

The big surprise for me in all of this was that it turns out I'm most interested in workflows and process! All of my sticky notes had the same theme: it wasn't tools, or data management, or social aspects that were causing me problems, but rather the development of appropriate workflows for scientific investigation. Very weird, and not what I would have predicted from the outset.

Two questions came up for me during the workshop:

Why don't people use workflows in bioinformatics?

The first question that comes to mind is, why doesn't anyone I know use a formal workflow engine in bioinformatics? I know they exist (Taverna, for one, has a bunch of bioinformatics workflows); I'm reasonably sure they would be useful; but there seems to be some block against using them!

What would the ideal workflow situation be?

During the anchor game, our group (which consisted of two biologists, myself and Hugh Shanahan; a physicist, Geoffrey Fox; and a few computer scientists, including Alex Wade) came up with an idea for a specific tool. The tool would be a bridge between Datascope for biologists and a workflow engine. The essential idea is to combine data exploration with audit trail recording, which could then be hardened into a workflow template and re-used.


Thinking about the process I usually use when working on a new problem, it tends to consist of all these activites mixed together:

  1. evaluation of data quality, and application of "computational" controls
  2. exploration of various data manipulation steps, looking for statistical signal
  3. solidifying of various subcomponents of the data manipulation steps into scripted actions
  4. deployment of the entire thing on multiple data sets

Now, I'm never quite done -- new data types and questions always come up, and there are always components to tweak. But portions of the workflow become pretty solid by the time I'm halfway done with the initial project, and the evaluation of data quality accretes more steps but rarely loses one. So it could be quite useful to be able to take a step back and say, "yeah, these steps? wrap 'em up and put 'em into a workflow, I'm done." Except that I also want to be able to edit and change them in the future. And I'd like to be able to post the results along with the precise steps taken to generate them. And (as long as I'm greedy) I would like to work at the command line, while I know that others would like to be able to work in a notebook or graphical format. And I'd like to be able to "scale out" the computation by bringing the compute to the data.

For all of this I need three things: I need workflow agility, I need workflow versioning, and I need workflow tracking. And this all needs to sit on top of a workflow component model that lets me run the components of the workflow wherever the data is.

I'm guessing no tool out there does this, although I know other people are thinking this way, so maybe I'm wrong. The Microsoft folk didn't know of any, though, and they seemed pretty well informed in this area :).

The devil's choice I personally make in all of this is to go for workflow agility, and ignore versioning and tracking and the component model, by scripting the hell out of things. But this is getting old, and as I get older and have to teach my wicked ways to grad students and postdocs, the lack of versioning and tracking and easy scaling out gets more and more obvious. And now that I'm trying to actually teach computational science to biologists, it's simply appallingly difficult to convey this stuff in a sensible way. So I'm looking for something better.

One particularly intriguing type of software I've been looking at recently is the "interactive Web notebook" -- ipython notebook and sagenb. These are essentially Mathematica or matlab-style notebook packages that work with IPython or Sage, scientific computing and mathematical computing systems in Python. They let you run Python code interactively, and colocate it with its output (including graphics); the notebooks can then be saved and loaded and re-run. I'm thinking about working one or the other into my class, since it would let me move away from command-line dependence a bit. (Command lines are great, but throwing them at biologists, along with Python programming, data analysis, and program execution all together, seems a bit cruel. And not that productive.)

It would also be great to have cloud-enabled workflow components. As I embark on more and more sequence analysis, there are only about a dozen "things" we actually do, but mixed and matched. These things could be hardened, parameterized into components, and placed behind an RPC interface that would give us a standard way to execute them. Combined with a suitable data abstraction layer, I could run the components from location A on data in location B in a semi-transparent way, and also record and track their use in a variety of ways. Given a suitably rich set of components and use cases, I could imagine that these components and their interactions could be executed from multiple workflow engines, and with usefully interesting GUIs. I know Domain Specific Languages are already passe, but a DSL might be a good way to find the right division between subcomponents.

I'd be interested in hearing about such things that may already exist. I'm aware of Galaxy, but I think the components in Galaxy are not quite written at the right level of abstraction for me; Galaxy is also more focused on the GUI than I want. I don't know anything about Taverna, so I'm going to look into that a bit more. And, inevitably, we'll be writing some of our own software in this area, too.

Overall, I'm really interested in workflow approaches that let me transition seemlessly between discovery science and "firing for effect" for hypothesis-driven science.

A few more specific thoughts:

In the area of metagenomics (one of my research focuses at the moment), it would be great to see img/m, camera, and MG-RAST move towards a "broken out" workflow that lets semi-sophisticated computational users (hi mom!) run their stuff on the Amazon Cloud and on private HPCs or clouds. While I appreciate hosted services, there are many drawbacks to them, and I'd love to get my hands on the guts of those services. (I'm sure the MG-RAST folk would like me to note that they are moving towards making their pipeline more usable outside of Argonne: so noted.)

In the comments to my post on Four reasons I won't use your data analysis pipeline, Andrew Davison reminds me of VisTrails, which some people at the MS workshop recommended.

I met David De Roure from myExperiment at the MS workshop. To quote, "myExperiment makes it easy to find, use, and share scientific workflows and other Research Objects, and to build communities."

David put me in touch with Carole Goble who is involved with Taverna. Something to look at.

In the cloud computing workshop I organized at the Planet and Animal Genome conference this January, I will get a chance to buttonhole one of the Galaxy Cloud developers. I hope to make the most of this opportunity ;).

It'd be interesting to do some social science research on what difficulties users encounter when they attempt to use workflow engines. A lot of money goes into developing them, apparently, but at least in bioinformatics they are not widely used. Why? This is sort of in line with Greg Wilson's Software Carpentry and the wonderfully named blog It will never work in theory: rather than guessing randomly at what technical directions need to be pursued, why not study it empirically? It is increasingly obvious to me that improving computational science productivity has more to do with lowering learning barriers and changing other societal or cultural issues than with a simple lack of technology, and figuring out how (and if) appropriate technology could be integrated with the right incentives and teaching strategy is pretty important.


p.s. Special thanks to Kenji Takeda and Tony Hey for inviting me to the workshop, and especially for paying my way. 'twas really interesting!

Syndicated 2011-12-11 15:00:57 from Titus Brown

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