# Question definitions
Mechanical Turk provides three XML schemas that you can use to define your questions:
+ [https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/ApiReference_HTMLQuestionArticle.html](https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/ApiReference_HTMLQuestionArticle.html)
+ [https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/ApiReference_ExternalQuestionArticle.html](https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/ApiReference_ExternalQuestionArticle.html)
+ [https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/ApiReference_QuestionFormDataStructureArticle.html](https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/ApiReference_QuestionFormDataStructureArticle.html)
Use the following topics to learn more about these schemas.
**Topics**
+ [`HTMLQuestion`](#mturk-hits-defining-questions-definitions-htmlquestion)
+ [`ExternalQuestion`](#mturk-hits-defining-questions-definitions-externalquestions)
+ [`QuestionForm`](#mturk-hits-defining-questions-definitions-questionform)
## `HTMLQuestion`
Most developers use the [https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/ApiReference_HTMLQuestionArticle.html](https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/ApiReference_HTMLQuestionArticle.html) schema to create HITs. `HTMLQuestion` wraps an HTML form that is displayed to workers. This typically takes the following form:
```
Describe the current weather where you live
]]>0
```
As you can see in the preceding XML, the HTML content is enclosed in a CDATA element within the XML and includes the elements that define how your question appears to workers. More information on defining your HTML can be found in [Use HTML to define questions](mturk-hits-defining-questions-html.md).
## `ExternalQuestion`
When you create a task using the `HTMLQuestion` format, your HTML is hosted by Mechanical Turk. Using Mechanical Turk to host your task helps ensure that it is in a highly available location. If, however, you want to host the task interface on your own servers or cloud resources, you can use the [https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/ApiReference_ExternalQuestionArticle.html](https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/ApiReference_ExternalQuestionArticle.html) format.
To use `ExternalQuestion`, your URL must meet the following criteria:
+ The location specified by the URL must support HTTPS.
+ The location must be highly available and able to respond quickly when workers accept or preview your task.
+ The URL cannot include any of the reserved query parameters (`assignmentId`, `hitId`, `turkSubmitTo`, and `workerId`) that is appended by Mechanical Turk, as described in [How Mechanical Turk tasks are rendered](mturk-hits-defining-questions-html-rendered.md).
+ The location specified by the URL must perform a form `POST` operation with the `assignmentId` when the task is completed, as described in [Use HTML to define questions](mturk-hits-defining-questions-html.md).
Amazon S3 is a great option for hosting your task HTML. When you use an S3-hosted layout, you need to add a `ContentType` header and set the ACL to public read, as shown in the following Python SDK `PutObject` call:
```
s3_client.put_object(
ACL='public-read',
Body=HTML layout,
Bucket=S3 bucket name,
Key=Object name,
ContentType="text/html"
)
```
When using this schema, you simply need to indicate the URL you want to use.
```
https://tictactoe.amazon.com/gamesurvey.cgi?gameid=015230
```
When you use `ExternalQuestion`, you can make the served HTML as complex or simple as necessary for your particular task. However, you must use of a form element to submit a POST to Mechanical Turk when the task is complete. This directs the browser to advance and notify Mechanical Turk that the task is complete.
## `QuestionForm`
`[QuestionForm](https://docs.aws.amazon.com/AWSMechTurk/latest/AWSMturkAPI/ApiReference_QuestionFormDataStructureArticle.html)` is a legacy XML format that can be used to define Mechanical Turk tasks using an XML schema. While it is still supported, we recommend building your task using `HTMLQuestion` or `ExternalQuestion`.