Skip to content
Samples using context variables and (system) entities in IBM Watson Assistant (formerly Conversation) service on IBM Cloud
Branch: master
Clone or download
Type Name Latest commit message Commit time
Failed to load latest commit information.
workspaces updates to README, new workspace Jun 27, 2017
LICENSE Initial commit Jun 20, 2017
Notice.txt add Notice, expand README Jun 20, 2017 Conversation to Assistant, Bluemix to Cloud Apr 30, 2019

Using variables with IBM Watson Assistant (formerly Conversation) service

The IBM Watson Assistant (Conversation) service on IBM Cloud is the foundation for building powerful chatbots and dialog-based systems. Core to its flexibility and versatility is a programming API and the ability to pass variables through the cognitive system. It supports user-provided context variables, allows the access to identified intents and entities including the annotations (what was the system thinking). Moreover, it features predefined system entities which can be enabled and significantly simplify detection of numbers, locations, people, dates and more within the ongoing conversation.

In this repository we are going to collect samples that demonstrate how those variables and metadata can be put to productive work.

The samples and the general syntax are described in the following blog posts. They can serve as additional source of information:



The following sample scenarios demonstrate how context variables, intents and entities including system entities can be used for customized dialogs.

Access to system entities

The IBM Watson Assistant service supports several system entities. They are predefined entities which can be enabled to allow simple identification of typical user input. The following response string shows how the entities can be accessed to form an answer.

Response string: All of <? entities.size() ?> entities: <? entities ?>. They include "sys-location" (<? entities['sys-location'] ?>), "sys-date" (<? entities['sys-date'] ?>), "sys-number" (<? entities['sys-number'] ?>), "sys-person" (<? entities['sys-person'] ?>) and more

How is the weather today in San Francisco and in Germany. Will it be over 20? Henrik and family want to go outside


All of 5 entities: San Francisco, Germany, Henrik, 2017-06-19, 20. They include "sys-location" (San Francisco, Germany), "sys-date" (2017-06-19), "sys-number" (20), "sys-person" (Henrik) and more

The example is part of the simple-variables.json workspace file. You can import the file as new workspace into IBM Watson Conversation.

Working with Currency

In this example a condition first checks that a system entity sys-currency is present, then that exactly two currency values are included in the user input and, as third condition, that the currency units match. In the response string the two entered values are added.

entities['sys-currency'] && entities['sys-currency'].size()==2 && entities['sys-currency'][0].unit==entities['sys-currency'][1].unit

Response string: You have <? entities['sys-currency'][0].value.toDouble() + entities['sys-currency'][1].value.toDouble() ?> <? @sys-currency.unit ?>

I have 20 USD and $24


You have 54.0 USD

Nested evaluation of variables

Sometimes it is necessary to first evaluate one variable and then use the result as input to another evaluation. In some programming / scripting language there is a special method or operator for this. An example is the eval function in Python. But how can you do something like this in Watson Assistant? There, evaluations are done inside the <? ?> expression.

The upper dialog node consists of an empty response (output). Only the context is evaluated and a new value assigned to the variables access and result (based on a computation):

  "context": {
    "access": "<? $myproperties['one'] ?>",
    "result": "<? $myproperties['two'] * @sys-number ?>"
  "output": {}

A subnode with the following response performs the second set of evaluations. It uses access and result as input. This is my nested response: <? context['access'] ?>. The result is <? context['result'] + context['result'] ?>.

If the dialog input is nested 8 and there is an existing context with"one" and myproperties.two=2, the following result is returned:

This is my nested response: one. The result is 32.

Conditions and predicates in the response

Dialog nodes in IBM Watson Conversation allow to check conditions (or predicates). Conditions control whether the node qualifies. Conditions can also be placed ahead of a response block inside a dialog node. In addition to that, conditions can even be placed and evaluated inside individual responses.

The following is a reponse string. It checks whether the location of entities in the input string and then returns one of two strings. It uses condensed ìf-then-else logic, a so-called ternary operator:

<? entities['airport'][0].location[0]<entities['airport'][1].location[0] ?
'First, then second' : 'Second comes first' ?>

Note that you can nest the expressions (if first expression, then do, else evaluate next expression):

  "context": {
    "number1": "<? @number1:mat3 ? entities.number1[2].literal :
          @number1:mat2 ? entities.number1[1].literal : entities.number1[0].literal ?>"

Replaced Markers

An alternative to embedding expressions into responses is to use special markers in the regular text:


The application code would then search for and replace the designated markers with information carried in the application. This could be overall simpler to do, especially when more complex data and structures are retrieved from backend systems and more sophisticated formatting and processing of that data is needed.

Hello Henrik, it is 16:54:31.

A simple example of the above can be seen in the TJBot "Tell the time" recipe. In the function tellTheTime the marker todays_date is replaced with the current time for a specific timezone.

In an advanced version of using markers, the entire response only consists of a marker. It would be replaced by the application by an answer that, maybe, is retrieved from a database or built from a template and data coming from various systems. The Watson Conversation Service would analyze and process the user input, but only return with a hint (the marker) on how to answer.


The above could be turned into:

Hello Henrik, it is 16:54:31.

Random output from variables

Sometimes, when using context variables or system metadata, you want to use a random (or other) portion of it in a response or when assigning a context variable. The following code shows how a mathematical function, here random(), is used to obtain an array entry and insert it into the response text:

Here is a random entity:
 <? entities[(entities.size() * T(java.lang.Math).random()).intValue()].value ?>

In the code the global entity array as part of the dialog metadata is used. A random number within the range of the array size is computed. The entity value is then accessed and printed.

Zeroes at the Slots

Slots are a great way to gather several pieces of information and to easily declare what is needed. However, sometimes "ease of use" and (mathematical) logic are not friendly to each other. The following is such an example: Waiting for @sys-number to accept a 0 (zero)

The condition @sys-number is in fact a short hand syntax for condition entities['sys-number'].value. When 0 is sent the condition is evaluated to false as 0 is treated as a false by the expression language evaluator in Watson Assistant. Now this is not a desired behavior in this case. To prevent this, you can use entities['sys-number'] in the condition that will return true every time @sys-number entity is recognized in the input. The Assistant documentation has some related usage tips.

Slack URIs as variables

I have been using Slack integrations with Watson Assistant. When trying to retrieve and identify URIs, e.g. web addresses or email addresses, coming from Slack as a patterned entity, I initially failed. The reason is that Slack formats the URIs into a style like <|>. Thus, I am using the following pattern to define email and web address entities: <[A-Za-z0-9._|:%@\/]+>.

Context Variable Defined

Sometimes it is not clear whether a certain value or context variable has been entered. One example is when working with slots and a handler is used to exit the input process. To check whether a context variable has been defined and to give a conditional answer, the following check can be used:

"<? context.myVariable? 'Great. I have the following: '+context.myVariable+'.' : 'No information present' ?>"

The question mark checks for existence and if present processes the first answer and, if not, the second option.

Delete Context Variables

At the end of processing input it often is necessary to clean up or reset the processing environment. This can be done by setting context variables to empty or null values. However, it is quite effective to remove the variable, so the environment is fresh again:

  "output": {
    "text": {},
    "deleted": "<? context.remove('eventName') ?> <? context.remove('queryPredicate') ?>"


For those on recent API versions of Watson Assistant:

Set the variable to null. Here is the doc on "Deleting a context variable".

  "context": {
    "myvariable": null

Collection Projection

A collection projection, by definition, extracts a subcollection from an array of values. The operator is denoted with a ! and is useful in many ways.

The following expression as part of an output object would print an array of the detected entity values for myentity.

{ "text": "<? entities['myentity'].![value] ?>"}

This expression would assign a comma-separated list of the words (literals) that are part of the input message:

  "context": {
    "myvariable": "<? entities['myentity'].![literal].join(', ')  ?>"

Documentation and Resources

Here are some useful links to documentation and other resources:


See LICENSE for license information.

The samples are provided on a "as-is" basis and are un-supported. Use with care...

Contribute / Contact Information

If you have found errors or some instructions are not working anymore, then please open an GitHub issue or, better, create a pull request with your desired changes.

You can find more tutorials and sample code at:

You can’t perform that action at this time.