Using functions in ROSPlan

[Stephen Balakirsky]

Hi,

I have a simple function in my PDDL file that can be reduced to:

(:functions

   (ordering_constraint ?o - object)

)

The function allows for constraints such as

(= (ordering_constraint object_1) 1)

(= (ordering_constraint object_2) 2)

I would like to be able to set these functions in ROSPlan with  a service call. It appears to me that this should be possible to the knowledgebase update service. However, I have been unable to either find an example or get this working on my own. Has anyone utilized functions with ROSPlan? Thanks.

Stephen

[Stephen Balakirsky]

I think that I got it...

rosservice call /rosplan_knowledge_base/update "update_type: 0

knowledge:

  knowledge_type: 2

  initial_time: {secs: 0, nsecs: 0}

  is_negative: false

  instance_type: ''

  instance_name: ''

  attribute_name: 'ordering_constraint'

  values:

  - {key: 's', value: 'object_1'}

  function_value: 2.0

  optimization: ''

  expr:

    tokens:

    - expr_type: 0

      constant: 0.0

      function:

        name: ''

        typed_parameters:

        - {key: '', value: ''}

      op: 0

      special_type: 0

  ineq:

    comparison_type: 0

    LHS:

      tokens:

      - expr_type: 0

        constant: 0.0

        function:

          name: ''

          typed_parameters:

          - {key: '', value: ''}

        op: 0

        special_type: 0

    RHS:

      tokens:

      - expr_type: 0

        constant: 0.0

        function:

          name: ''"

[Michael Cashmore]

You got it.

There is some more information here:

https://kcl-planning.github.io/ROSPlan//tutorials/tutorial_08

The function value can also be set in a PDDL problem file loaded into the KB, and the function call can be made from code. Python and bash examples below.

```python

ki = KnowledgeItem()

ki.attribute_name = "ordering_constraint"

ki.knowledge_type = ki.FUNCTION

kv = KeyValue()

kv.key = "o"

kv.value = "object_1"

ki.values.append(kv)

ki.function_value = 2.0

```

```

#!bin/bash

rosservice call /rosplan_knowledge_base/update "update_type: 0

knowledge:

  knowledge_type: 2

  attribute_name: 'ordering_constraint'

  values:

  - {key: 's', value: 'object_1'}"

  function_value: 2.0

```

Michael