The conversations a bot has with its users are controlled by the content of its dialog. Dialogs contain templates for messages the bot will send, along with instructions for the bot to carry out tasks. While some dialogs are linear - just one message after the other - more complex interactions will require dialogs that branch and loop based on what the user says and the choices they make. This article explains how to add both simple and more complex conversation flow using example from the ControllingConversationFlowSample.
Bot Framework Composer offers several mechanisms for controlling the flow of the conversation. These building blocks instruct the bot to make a decision based on a property in memory or the result of an expression. Below is a screenshot of the Create a Condition menu:
-
Branch: If/Else instructs the bot to choose between one of two paths based on a
yes/noortrue/falsetype value. -
Branch: Switch (multiple options) branch instructs the bot to choose the path associated with a specific value - for example, a switch can be used to build a multiple-choice menu.
-
Loop: for each item instructs the bot to loop through a set of values stored in an array and carry out the same set of actions with each one. For very large array there is Loop: for each page (multiple items) that can be used to step through the array one page at a time.
The Branch: If/Else action creates a decision point for the bot, after which it will follow one of two possible branches. To create an Branch: If/Else branch click the + icon under your trigger, mouse over Create a Condition, and click Branch: If/Else.
The decision is controlled by the Condition field, which should contain an expression that evaluates to true or false. In the screenshot below the bot is evaluating whether user.age is greater than or equal to 18.
Once the condition has been set, the corresponding branches can be built. The editor will now display two parallel paths in the flow - one that will be used if the condition evaluates to true, and one if the condition evaluates false. Below the bot will Send a response based on whether user.age>=18 evaluates to true or false.
In a Branch: Switch result, the value of the Condition field is used to choose between any number of pre-set paths. Each path is tied to one possible value of the condition. To create a Branch: Switch branch click the + icon under your trigger, mouse over Create a Condition, and click Branch: Switch.
Like Branch:If/Else you set the Condition to evaluate in the property panel on the right. Underneath at you can create Branches in your switch condition by entering the value and clicking Enter. As each case is added, a new branch will appear in the flow which can then be customized with actions. See below how the Nick and Tom branches are added both in the property panel on the right and in the authoring canvas.
In addition to any cases created, there will always be a "default" branch which will be used if none of the other cases match.
Loop: for each item action instructs the bot to loop through a set of values stored in an array and carry out the same set of actions with each one. To create a Loop: for each item loop click the + icon under your trigger, mouse over Create a Condition, and click Loop: for each item.
On the right in the property panel you will see Items property. This is where you enter the array property to be iterated.
After setting the properties you then decide what action your bot should perform in the array. In this sample the bot sends the the result of the expression @{dialog.foreach.index}: @{dialog.foreach.value}.
Once the loop begins, it will repeat once for each item in the array of items. Note that it is not currently possible to end the loop before all items have been processed. If the bot needs to process only a subset of the items, use Branch: If/Else and Branch: Switch branches within the loop to create further conditional paths.
Loop: for each page (multiple items) loops are useful for situations in which you want to loop through a large array one page at a time. Like Loop: for each item loops the bot iterates an array, but the difference is that For Each Loops executes actions per item page instead of per item in the array.
To create a Loop: for each page (multiple items) loop click the + icon under your trigger, mouse over Create a Condition, and click Loop: for each page (multiple items).
On the right you will see the Items Property of the array to iterate and the Page size, or number of items to include in each page array.
After setting the aforementioned properties your Loop: for each page (multiple items) loop is ready. As seen in the sample below, you can nest for Loop: for each item within your Loop: for each page (multiple items) loop, causing your bot to loop through all the items in one page and take an action before handling the next page.
In addition to conditional branching and looping, it is also possible to compose multiple dialogs into a larger more complex interaction. Below are the available Dialog management options:
Child dialogs can by called clicking the + arrow underneath the trigger, mousing over Dialog management and clicking Begin a new dialog.
When the child dialog begins, the parent dialog pauses until the child dialog completes, then resumes where it left off.
It is possible to pass parameters into the child dialog. Parameters can be added to the Begin a new dialog action as name/value pairs - the value of each parameter can be a property in memory or an expression.
In the example above, the child dialog menu will be started, and will be passed 2 options:
- the first will contain the value of the property
dialog.option1and be available inside the menu dialog asdialog.options.option1 - the second will contain the value of the property
user.preferenceand will available inside the menu dialog asdialog.options.option2
Note that it is not necessary to map memory properties that would otherwise be available automatically - that is, the user and conversation scopes will automatically be available for all dialogs. However, values stored in the turn and dialog scope do need to be explicitly passed.
In addition to passing values into a child dialog, it is also possible to receive a return value from the child dialog. This return value is specified as part of the End this dialog action, as described below.
In addition to Begin a new dialog, there are a few other methods for launching a child dialog.
Replace this Dialog works just like Begin a new dialog, with one major difference: the parent dialog does not resume when the child finishes. To replace a dialog click the + button, mouse over Dialog management, and select Replace this Dialog.
Repeat this Dialog causes the current dialog to repeat from the beginning. Note that this does not reset any properties that may have been set during the course of the dialog's first run. To repeat a dialog click the + button, mouse over Dialog management, and select Repeat this Dialog.
Any dialog called will naturally end and return control to any parent dialog when it reaches the last action it the flow. It is not necessary to explicitly call End this dialog.
It is sometimes desirable to end a dialog before it reaches the end of the flow - for example, you may want to end a dialog if a certain condition is met.
Another reason to call the End this dialog action is to pass a return value back to the parent dialog. The return value of a dialog can be a property in memory or an expression, allowing developers to return complex values if necessary. To end a dialog click the + button, mouse over Dialog management, and select End this dialog.
Imagine a child dialog used to collect a display name for a user profile. It asks the user a series of questions about their preferences, finally helping them enter a valid user name. Rather than returning all of the information collected by the dialog, it can be configured to return only the user name value, as seen in the example below. The dialog's End this dialog action is configured to return the value of dialog.new_user_name to the parent dialog.
In addition to creating explicit branches and loops in the flow, it is also possible to create conditional versions of messages using the Language Generation syntax. The LG syntax supports the same common expression language as is used in the action blocks.
For example, you can create a welcome message that is different depending on whether the user.name property is set or not. The message template could look something like this:
- IF: @{user.name != null}
- Hello, {user.name}
- ELSE:
- Hello, human!
Learn more about using memory and expressions in LG.