An introduction to Taverna workflows

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An introduction to Taverna workflows Franck Tanoh

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1. Installing the Workbench
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Exercise 1 Installing the Workbench

• Download Taverna from http//taverna.sourceforge.n
  et
• Windows or linux
• If you are using either a modern version of
  Windows (Win2k or WinXP, with XP preferred) or
  any form of linux, solaris etc. you should
  download the workbench zip file. For windows
  users, Taverna can be unzipped and used, for
  linux you will also need to install GraphViz
  (http//www.graphviz.org/ the appropriate rpm for
  your platform)
• Mac OSX
• If you are using Mac OSX you should download the
  .dmg workbench file. Double-click to open the
  disk image and copy both components (Taverna and
  GraphViz) onto your hard-disk to run the
  application
• YOU WILL ALSO NEED a modern Java Runtime
  Environment (JRE) or Java Software Development
  Kit (SDK) from http//java.sun.com Java 5 or above

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• Taverna workbench has a standard menu of 6 tabs
• File with 9 items
• 
  

• Open a new workspace
• Load a workflow from a file
• Load a workflow from the web
• Close existing workflow
• Save workflow
• Import workflow from a file
• Import workflow from the web
• Run your workflow
• Close the workbench

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• Tools for plug-in and updates
• Workflow list of all created workflow
• Advanced to create new perspectives
• Design Workflow design space
• Result view workflow results

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• Taverna Design view is composed of 3 main
  windows
• 1- Available Services
• Lists services available by default in Taverna
• Local java services
• Simple web services
• Soaplab services legacy command-line
  application
• BioMart database services
• BioMoby services
• Allows the user to add new services or workflows
  from the web or from file systems

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Workbench Layout

• 2- AME Advanced Model Explorer
• The Advanced Model Explorer (AME) is the primary
  editing component within Taverna. Through it you
  can load, save and edit any property of a
  workflow. It enables
• -building
• -loading
• -editing
• -saving workflows

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• 3- Workflow Diagram Window
• Visual representation of workflow
• Shows inputs / outputs, services and control
  flows
• Enables saving of workflow diagrams for
  publishing and sharing

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• Take 1 to 5 minutes to familiarise yourselves
• with Taverna workbench

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Installing Plugins

• Go to the Tools menu at the top of the
  workbench and select the Plugin manager
• Select find new plugins
• Tick the boxes for Feta, Execute remotely and
  LogBook and install these plugins
• Three more options Execute remotely, Discover
  and LogBook will now have appeared at the top
  of your screen
• Feta is now available through the Discover tab
• The Discover tab can be used to search for web
  services by name, task, input and output
  parameters

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2. Adding new services
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Exercise 2 Adding New Services

• New services can be gathered from anywhere on the
  web
• Go to the following page http//developerdays.com
  /cgi-bin/tempconverter.exe/wsdl/ITempConverter
  and copy the web page address
• These services were not designed for use in
  Taverna, but Taverna can use them if you supply
  the address of the WSDL file

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Exercise 2 Adding New Services

• Go to the Available services panel and
  right-click on Available Processors. For each
  type of service, you are given the option to add
  a new service, or set of services.
• Select Add new wsdl scavenger. A window will
  pop-up asking for a web address
• Enter the Web service address you have just
  copied.
• Scroll down to the bottom of the Available
  Services panel and look at the Temperature
  Conversion web service that is now included.

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3. Finding and Invoking a Service
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Exercise 3Invoking a single service

• Expand the next to tempconverter (the
  Temperature Conversion) web service
• Right click on the CtoF operation and select
  Invoke. This operation converts a temperature
  from Celsius to Fahrenheit.
• In the pop-up Run workflow window add a
  Temperature value in Celsius by selecting temp
  and right-clicking. Select new input value and
  enter a value in the box on the right
• Click Run workflow and the service is invoked

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Exercise 3 View Results

• Click on text/plain in the left panel
• The temperature in Fahrenheit is displayed on the
  Right
• Click on Process Report
• Look at processes. This shows the experiment
  provenance where and when processes were run
• Click on Status
• Look at options As workflows run, you can monitor
  their progress here.

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Exercise 3 - Conclusion

• The processes for running and invoking a single
  service are the basics for any workflow and the
  tracking of processes and generation of results
  are the same however complicated a workflow
  becomes
• In the next few exercises, we will look at some
  example workflows and build some of our own from
  scratch

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4. Finding and Using Workflows
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Exercise 4 Finding and using workflows

• Switch to the design view by clicking on Design
• Select Open Workflow from the File menu at the
  top of the workbench. You will see a selection of
  .xml files in an examples directory. These are
  workflow definition files
• Select ConvertedEMBOSSTutorial.xml and a
  pre-defined workflow will be loaded
• View the workflow diagram - you will see services
  of in different colours

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Exercise 4 Workflow Documentation

• Find out what the workflow does by reading the
  workflow metadata
• In the AME click on the name of the workflow
  in this case A workflow version of the EMBOSS
  tutorial and then select the workflow metadata
  tab at the top of the AME. You will see a text
  description of the workflow, its author and its
  unique LSID. When publishing workflows for
  others, this annotation is useful information and
  allows the acknowledgement of intellectual
  property

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Exercise 4 Workflow Features

• Run the workflow by selecting run workflow from
  the file menu
• Watch the progress of the workflow in the
  enactor invocation window. As services
  complete, the enactor reports the events. If a
  service fails, the enactor reports this also

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Loading workflows from the Web

• Go to the webpage www.cs.man.ac.uk/ytanoh
• Select ConditionalBranchChoice and copy the web
  address
• Go back to the Taverna workbench and select Open
  workflow location from the file menu.
• Paste the address in the pop up window and click
  ok
• Run the workflow using true or false as input
  value.

• Go to the webpage www.cs.man.ac.uk/ytanoh
• Select ConditionalBranchChoice and copy the web
  address
• Go back to the Taverna workbench and select Open
  workflow location from the file menu.
• Paste the address in the pop up window and click
  ok
• Run the workflow using true or false as input
  value.

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Loading workflows from the Web

• You will see at least one of the services fail.
  What happens when it fails depends on whether the
  service is set as a critical one. If it is, the
  workflow will abort, if it isnt, the workflow
  will continue
• You can set a workflow to critical by ticking the
  critical box in the AME.
• Set the workflow to critical and run it again
• The entire workflow fails this time.

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Loading workflows from the Web

• Go back to the Design view
• Look at the workflow diagram
• You will see black arrows and white circles
  black arrows show the flow of the data and white
  circles are control links.
• A control link specifies that even though there
  is no data flowing between two services, the
  second should not start until the end of the
  first

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56 Building a simple workflow
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5.1 Building a simple workflow from scratch

• Open a new workspace by Selecting New workflow
  from the file menu.
• Then find the CtoF service in the Available
  services panel (you can use the search form on
  top of Available Processors).
• Right-click on CtoF and import it into the
  workbench by selecting Add to Model
• In the AME window CtoF shows
• 1 input (Green arrow pointing up)
• 2 output (purple arrow pointing down)

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Exercise 5.2 Adding Input

• Define a new workflow input by right-clicking on
  Workflow Input and selecting create new
  Input
• Supply a suitable name e.g. temperatureInCelsius
  
• Connect this new input to the CtoF service by
  right-clicking on temperatureInCelsius and
  selecting CtoF gttemp
• You always build workflows with the flow of data

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Exercise 5.3 Adding output

• Define a new workflow output by right-clicking on
  workflow output and selecting create new
  output
• Supply a suitable name e.g. temperatureInFahrenhe
  it
• Connect this new output to the CtoF service
  output (return). (right-click the output return
  on CtoF service and select workflow output -gt
  temperatureInFahrenheit)
• Congratulation! You have built a simple
  workflow from scratch.
• Run the workflow. You will again need to supply a
  temperature value in Celsius, e.g. 25

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Exercise 6 Stringing Services Together

• In the following section you will learn to
  connect more than one services together.
• In the first exercise of this section, you are
  going to convert a temperature value from Celsius
  to Fahrenheit then back to Celsius again using
  only one workflow.
• Open a new workflow workspace
• Search for CtoF web service in the Available
  services panel and add it to the AME window.
• Search for FtoC web service in the Available
  services panel and add it to the AME window.
• Create a input called TempC and connect it to
  temp input on CtoF service

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Exercise 6 Stringing Services Together

• The temperature input for the FtoC service will
  be the output from the CtoF service. Connect
  the output return on CtoF web service to the
  input temp on FtoC web service .
• Create two outputs called temp_in_C and
  temp_in_F, and connect them respectively to the
  output return on CtoF service and to the
  output return on FtoC service.
• Remember You always build workflows
  with the flow of data
• Run the workflow
• NB A web service output (e.g. return) can be
  connected to more than one workflow outputs or
  web services input.

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Exercise 6 String Constants

• Go back to the workflow you created
• Select and right-click the workflow input TempC
  
• Select Remove from model to delete it.
• Select string constant from Available
  Services
• Right-click and select add to model with name
• Insert TemperatureC in the pop-up window
• Right-click on TemperatureC and select Edit
  string value
• Enter a temperature value in Celsius.
• Connect the output value on TemperatureC to
  the input temp on CtoF service.
• Run the workflow- The workflow will run with the
  default value

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Exercise 6 Stringing Services Together

• In the second exercise of this section, you are
  going to retrieve a comic image (Daily Dilbert)
  from the web.
• Open a new workflow workspace
• Add the following wsdl service http//www.esynaps.
  com/WebServices/DailyDiblert.asmx?WSDL
• Add the service DailyDilbertImagePath in the
  AME window.
• It has 2 outputs but no input.

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Exercise 6 Stringing Services Together

• Select the output parameter on
  DailyDilbertImagePath service
• Right-click and select add XML splitter
• A new service parametersXML is added with its
  input connection already made. This type of
  services (DailyDilbertImagePath) are known as
  complex type services.
• Search for Get image from URL web service and
  add it to the AME window.
• Connect the output DailyDilbertImagePathResult
  on ParametersXML service to the input url on
  Get image from URL service.

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Exercise 6 Stringing Services Together

• The second input base on Get image from URL
  service is optional. Leave it unconnected.
• Create a new workflow output DailyDilbert and
  connect it to the output image on Get image
  from URL service.
• Run the workflow

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Saving Results

• Taverna provides several options for saving data.
  
• Individual data items can be saved by
  right-clicking on them
• All data can be saved to disk
• Textual/tabular data can be saved to excel
• Save all the data from your workflow

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Try it

• Build a workflow following the model below. The
  web services (purple and green colour) names and
  input values are given in the diagram. Hint-use
  the Discover tab to find the services.
• Annotate your workflow (name, author, date)

• Run the workflow

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Advanced Exercises

• The previous exercises have covered the basics of
  myGrid workflows. The following demos and
  exercises cover more advanced features, such as
  rendering output, dealing with service failure
  and iterating over datasets. You may not reach
  the end of these exercises, but they will provide
  some examples to take home

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Exercise 8 Defining Output Formats

• Taverna is able to display results using a
  specific type of renderer if the workflow output
  is configured correctly.
• Load the workflow convertedEMBOSSTutorial from
  the examples directory
• Run the workflow

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Exercise 8 Defining Output Format

• Look at the results. For tmapPlot and
  outputPlot, you will see the results are
  displayed graphically. This is achieved by
  specifying a particular mime type in the output.
• Go back to the AME and look at the metadata for
  tmapPlot and outputPlot (e.g. select
  tmapPlot and click on Metadata for tmapPlot).
  
• Select MIME Types. As you can see, each has the
  image/png mime type associated with it. If you
  wish to render results in anything other than
  plain text, you MUST specify the mime-type in the
  workflow output

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Exercise 8 Taverna MIME-Types

• The following mime-types are currently used by
  Taverna
• text/plainPlain Text
• text/xmlXML Text
• text/htmlHTML Text
• text/rtfRich Text Format
• text/x-graphvizGraphviz Dot File
• image/pngPNG Image
• image/jpegJPEG Image
• image/gifGIF Image
• application/zipZip File
• chemical/x-swissprotSWISSPROT Flat File
• chemical/x-embl-dl-nucleotideEMBL Flat File
• chemical/x-ppdPPD File
• chemical/seq-aa-genpeptGenpept Protein
• chemical/seq-na-genbankGenbank Nucleotide
• chemical/x-pdbProtein Data Bank Flat File
• chemical/x-mdl-molfile

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Exercise 8 Taverna MIME types(2)

• The chemical/ mime-types are rendered using
  SeqVista to view formatted sequence data
• Load FetchPDBFlatFile from the
  examples/library directory
• Run the workflow using 1atp as input example
• The chemical/x-pdb can be used to view rotating
  3D protein images

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Advanced Features

• Iteration
• Control Flow
• Substituting Services and fault tolerance

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Iteration

• Taverna has an implicit iteration framework. If
  you connect a set of data objects (for example, a
  set of fasta sequences) to a process that expects
  a single data item at a time, the process will
  iterate over each sequence
• Load the BiomartandEMBOSSAnalysis.xml workflow
  from the examples directory and run it.
• Watch the progress report. You will see several
  services with Invoking with Iteration

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Iteration

• The user can also specify more complex iteration
  strategies using the service metadata tag
• Load the IterationStrategyExample.xml from the
  example directory
• Read the workflow metadata to find out what the
  workflow does
• Select the ColourAnimals service and read the
  metadata for that service. Under the description
  is the iteration strategy
• Click on dot product. This allows you to switch
  to cross product

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Iteration

• Run the workflow twice once with dot product
  and once with cross product.
• Save the first results so you can compare them
  what is the difference? What does it mean to
  specify dot or cross product?

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Substituting services and fault Tolerance

• Taverna does not own many of the services it
  provides. This means that it cannot control their
  reliability. Instead, Taverna provides strategies
  for dealing with services being unavailable
• Reload the convertedEMBOSSTutorial.xml from the
  examples directory.
• Look at the metadata for the emma service. It
  is an implementation of clustalw
• Find the DDBJ clustalw service analyseSimple,
  HINT use the Feta discovery tool

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Substituting Services

• When you have added this service to your
  workflow, right-click on it and select add as
  alternate
• In the resulting menu select emma
• The DDBJ version of the clustalw service is now
  added as an alternative to emma in the AME. It
  will be called alternate1
• Select alternate1 and look at the inputs and
  outputs. These need to be mapped to the correct
  inputs and outputs in emma

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Substituting Services

• Right-click on the query input in alternate1
  and map it to sequence_direct_data. In both
  services, these inputs expect a set of fasta
  sequences.
• Right-click on the result output and map it to
  outseq in emma in the same way.
• Now you have a workflow which will run using emma
  when it is available but will substitute it for
  DDBJ clustalw if emma fails!

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Fault Tolerance

• Taverna also allows the user to specify the
  number of times a service is retried before it is
  considered to have failed. Sometimes network
  traffic is heavy, so a working service needs to
  be retried
• Select tmap from the same workflow. To the
  right of the service name are a series of 0s and
  1s. By simply typing the numbers, the user can
  specify the number of retries and the time
  between the retries
• Change it to 3 retries for tmap and set the
  status to critical using the final tickbox. Now
  it is critical, it means the whole workflow will
  be aborted if tmap fails after 3 retries.
  Failures in non-critical services will not abort
  the workflow run.

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Shim Services

• A shim is a service that doesnt do anything
  scientific, but helps two scientific services fit
  together
• There are many myGrid shim services. These are
  currently being described in a shim library, but
  for now, a small collection are documented here
• http//www.cs.man.ac.uk/hulld/shims.html

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Shim Services

• Beanshell script
• Beanshell scripts allow users to write small,
  bespoke java scripts to allow incompatible
  service to work together
• More information on the beanshell script can be
  found in Taverna documentation
  http//www.mygrid.org.uk/usermanual1.6/beanshell_p
  rocessor.html

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Useful links

• Taverna supports R-scripts http//www.mygrid.org
  .uk/usermanual1.6/rshell_processor.html
• Taverna user manual http//www.mygrid.org.uk/user
  manual1.6/
• Taverna mailing lists http//taverna.sourceforge.
  net/index.php?doclists.html