simple-amt

simple-amt is a microframework for working with Amazon's Mechanical Turk (AMT). It was designed with the following three principles in mind:

• Abstract away the details of AMT to let you focus on your own task.
• Place no restrictions on the structure of your AMT tasks.
• Lightweight and easy to understand.

Quick start guide

Follow these steps to set up simple-amt and run a simple HIT on AMT.

Check out the codebase and set up a virtualenv

git clone https://github.com/jcjohnson/simple-amt.git
cd simple-amt
virtualenv .env
source .env/bin/activate
pip install -r requirements.txt

Configure your Amazon account

To use AMT, you'll need an Amazon AWS account. To interact with Amazon, simple-amt needs an access key and corresponding secret key for your Amazon account. You can find these here. Once you have these, place then in a file called config.json for simple-amt:

cp config.json.example config.json
# edit config.json; fill out the "aws_access_key" and "aws_secret_key" fields.

WARNING: Your AWS keys provide full access to your AWS account, so be careful about where you store your config.json file!

Launch some HITs

We've included a sample HIT that asks workers to write sentences to describe images. To launch a couple of these HITs on the AMT sandbox, run the following:

python launch_hits.py \
  --html_template=hit_templates/image_sentence.html \
  --hit_properties_file=hit_properties/image_sentence.json \
  --input_json_file=examples/image_sentence/example_input.txt \
  --hit_ids_file=examples/image_sentence/hit_ids.txt

This is the most complicated command that you will need to run; let's break it down:

• The file image_sentence.html is a simple jinja2 template that defines the UI of the HIT; you can find it in hit_templates/image_sentence.html.
• The file hit_properties/image_sentence.json defines the properties of the HIT: title, keywords, price, etc.
• The file examples/image_sentence/example_input.txt contains inputs for the HITs that you want to create. The input to each HIT is a JSON object, and the input file contains one such JSON object per line. One HIT is created for each line of the input file.
• The IDs of the created HITs are written to the file examples/image_sentence/hit_ids.txt. You will use this file as input to other commands in order to operate on the batch of HITs that you just created.

Note: You may be seeing an error message scrolling repeatedly if you're setting up AMT for the first time, asking you to "Please log in to https://requestersandbox.mturk.com/ and complete registration." You have to register on that URL first and then run again.

Do your HITs

Your HITs should now be live on the Mechanical Turk sandbox. Open the sandbox and sort by "HIT creation data (newest first)". You should see a HIT with the title "Write sentences to describe images" in the first page or two of results. Complete one of the HITs.

The HIT can sometimes take several seconds to appear. You can double check that the HIT is up and available by going to the requester sandbox page and clicking manage -> manage hits individually.

Also note that you may not satisfy the qualifications of your own HIT. In this case you can edit the file hit_properties/image_sentence.json and erase the lines corresponding to HitsApproved and PercentApproved. Remember to bring down the HITs you've launched (see below), and then re-launch the HIT (see above).

Check HIT progress

You can check the status of your in-progress HITs by running the following command:

python show_hit_progress.py --hit_ids_file=examples/image_sentence/hit_ids.txt

Get HIT results

You can fetch the results of your completed HITs by running the following command:

python get_results.py \
  --hit_ids_file=examples/image_sentence/hit_ids.txt \
  > examples/image_sentence/results.txt

The results of all completed HITs are now stored as in the file examples/image_sentence/results.txt. Each line of the file contains a JSON blob with the results from a single assignment.

If you collect your results before all your hits have been completed and need to call get results again, you can optimize the function by passing in the results you have already collected using the following command:

python get_results.py \
  --hit_ids_file=examples/image_sentence/hit_ids.txt \
  --output_file=examples/image_sentence/results.txt \
  > examples/image_sentence/results.txt

Approve work

If you are satisfied with the results that you have gotten, you can approve all completed assignments from your HIT batch by running the following command:

python approve_hits.py --hit_ids_file=examples/image_sentence/hit_ids.txt

Or if you want to approve individual assignments, you can save all the assignments id in a file assignment_ids.txt and then call the following command:

python approve_assignments.py --assignment_ids_file=examples/image_sentence/assignment_ids.txt

Delete HITs

Once your HITs are completed and you have saved the results, you can delete the HITs from Amazon's database with the following command:

python delete_hits.py --hit_ids_file=examples/image_sentence/hit_ids.txt

WARNING: After running this command, your HITs will no longer be visible to workers, and you will no longer be able to retrieve HIT results from Amazon. Make sure that you have saved the HIT results before running this command.

Get All HITs

In the event that you want to get the results for all the hits that you have launched on mtc, regardless of what their hit ids are, you can call the following function. It will save a json array where every element is a hit result.

python get_all_hits.py \
  > examples/image_sentence/all_results.txt

Rejecting Work

If you are unhappy with the work done and want to reject the work, you can call the following command (please note that rejecting work harms worker's rating on the site and can influence their ability to find other work):

python reject_hits.py --hit_ids_file=examples/image_sentence/hit_ids.txt

Or you can also reject individual assignments:

python reject_assignments.py --assignment_ids_file=examples/image_sentence/assignment_ids.txt

You can also delete individual hit ids from the command line:

python delete_hit.py --hit_id THE_HIT_ID_YOU_WANT_TO_DISABLE

Blocking Workers

In extreme cases, when you want to prevent a malicious worker from affecting your work, you can use the following commands to block or unblock them using their worker ids. Save the worker ids that you want to block in a file (e.g. worker_ids.txt) and call the following to block workers:

python block_workers.py --worker_ids_file=examples/image_sentence/worker_ids.txt

or to unblock workers:

python unblock_workers.py --worker_ids_file=examples/image_sentence/worker_ids.txt

Running on the production site

To run your HITs on the production AMT site, simply append a --prod flag to each of the above commands.

WARNING: Running HITs on sandbox is free, but running HITs on the production site is not. In order to launch HITs your Mechanical Turk account must have sufficient funds to pay for all HITs; these funds will be held in escrow by Amazon once you launch HITs, and will be paid to workers when you approve assignments.

Creating your own HITs

To create your own HITs, you'll need to do the following:

1. Create HTML template for HIT UI
2. Create HIT properties file
3. Prepare input file

We'll walk through each of these steps in more detail.

Build HIT UI

Building the UI is typically the most time-consuming step in creating a new type of HIT. You will have to do most of the work yourself, but simple-amt can still help. As a running example, we will use the UI defined in hit_templates/simple.html. This is a very basic HIT that asks workers to write an example of a category, like a type of dog or a flavor of ice cream.

If you look at hit_templates/simple.html, you'll notice that it looks like regular HTML except for the line

{% include "simpleamt.html" %}

This includes the file hit_templates/simpleamt.html, which does two things:

1. Sets up DOM elements where HIT input and output will be stored; the only one of these that you need to know is the submit button, which has the ID #submit-btn.
2. Sets up a global Javascript object called simpleamt that defines functions for working with Mechanical Turk on the frontend.

The Javascript simpleamt object provides the following functions:

• simpleamt.getInput(default_input): Attempts to get and parse the input JSON blob to this HIT. If this succeeds, the input JSON blob is returned as a Javascript object. If the input blob cannot be read (either during development when there is no input blob or if it cannot be parsed as valid JSON) then default_input is returned instead. If default_input is not passed to getInput then it defaults to null.
• simpleamt.setOutput(output): Store the output JSON blob for this HIT. output should be a Javascript object that can be serialized to JSON.
• simpleamt.isPreview(): Check to see if this HIT is in preview mode. Amazon uses a url parameter called assignmentId to indicate whether a HIT is being previewed. If the parameter does not exist (such as during development) then simpleamt.isPreview returns false.
• simpleamt.setupSubmit(): This performs a bit of bookkeeping to make it possible to submit results to Amazon. You must call this before the submit button is clicked; if you don't then Amazon will report an error when the user tries to submit the HIT.

To see a minimal example of these functions in action, look at the file hit_templates/simple.html.

While developing a HIT template, you will need to render the template to produce a valid HTML page that you can view in a browser. You can do this using the render_template.py script. Use it like this:

python render_template.py --html_template=hit_templates/simple.html --rendered_html=rendered_templates/simple.html

The rendered template will be stored in a directory called rendered_templates (you can change this by passing in the complete destination path of where you want the html rendered file to be saved.). Whenever you change your HIT template you will need to rerender to see your changes.

To actually view the rendered template in a web browser, you will need to run a local HTTP server so that protocol-relative URLs resolve properly. Python makes this very easy; just run

python -m http.server 8080

then point your web browser at http://localhost:8080/.

Create HIT properties file

To launch HITs, you need both an HTML template defining the UI for the HIT and a JSON file storing properties of the HIT. An example JSON file is hit_properties/simple.json. A HIT properties JSON file has the following fields (some are required and some are optional):

• Title: Required. Must be a string. The title of your HIT. This will be the first part of your HIT that workers see, so it should be short and descriptive.
• Description: Required. Must be a string. If a worker is intrigued by your HIT title, they can click on it to see the description. This should be a couple of sentences at most, giving a brief description of the HIT.
• Keywords: Required. Must be a string of words separated by commas. These keywords are used by Mechanical Turk's search function. From my experience the Mechanical Turk search function isn't very smart, so it can help to explicitly conjugate verbs, include both singular and plural versions of nouns, and be creative to think of words that could be relevant. Picking good keywords for your HIT is a basically a small SEO problem.
• Reward: Required. Must be a number. This is the amount of money (in US dollars) that will be paid to workers per assignment. Keep in mind that Amazon charges the greater of 20% or 0.1 cents as a commission fee, so your actual cost per HIT will be slightly higher than the reward. You should also always pay at least 5 cents per HIT to avoid paying unnecessary commission fees to Amazon.
• AssignmentDurationInSeconds: Required. Must be an integer. This is the number of time (in seconds) that each worker has to complete the HIT before it expires. You should probably make this about 2 to 3 times the actual amount of time that you expect workers to spend on each assignment.
• FrameHeight: Required. Must be an integer. When you HIT is displayed, Amazon renders the HIT content inside of an iframe. The height of the iframe is FrameHeight pixels. You should pick a number that is larger than your actual HIT content; if you don't then your HIT will be ugly and have nested scroll bars.
• MaxAssignments: Required. Must be an integer. The number of assignments to create for each input. This means that MaxAssignments different workers will give you results for each HIT input.
• Country: Optional. Must be a string. If you set this, then only workers from the specified country will be allowed to work on your HITs. This must be either a valid ISO 3166 country code or a valid ISO 3166-2 subdivision code. I usually just use "US".
• HitsApproved: Optional. Must be an integer. If you set this, then only workers who have had at least this many HITs approved on Mechanical Turk will be allowed to work on your assignments.
• PercentApproved: Optional. Must be an integer. If you set this, then only workers who have had at least this percent of their submitted HITs approved will be allowed to work on your HITs.
• QualificationId: Optional. If you have assigned qualifications to some workers, then this is only allow those workers with this qualification id to work on your hits.
• QualificationComparator: Optional. Must be one of <, =, or >. This helps decide whether you want the workers to have a qualification that is greater, equal or less than the QualificationInteger.
• QualificationInteger: Optional. Must be an integer. The value used to threshold workers to be above, equal or below (determined by QualificationComparator).