```python
declare_model = {
    'existence': {
        'Order': {'support': 1.0, 'confidence': 0.95},
        'Invoice': {'support': 1.0, 'confidence': 0.92},
        'Payment': {'support': 1.0, 'confidence': 0.88},
        'Goods Receipt': {'support': 1.0, 'confidence': 0.90},
    },
    'absence': {},
    'exactly_one': {},
    'init': {
        'Order': {'support': 1.0, 'confidence': 1.0},
    },
    'responded_existence': {
        'Order': {'support': 1.0, 'confidence': 0.98},
        'Invoice': {'support': 1.0, 'confidence': 0.95},
        'Goods Receipt': {'support': 1.0, 'confidence': 0.96},
    },
    'coexistence': {
        'Order': {'support': 1.0, 'confidence': 0.97},
        'Invoice': {'support': 1.0, 'confidence': 0.93},
        'Goods Receipt': {'support': 1.0, 'confidence': 0.94},
    },
    'response': {
        'Order': {'support': 1.0, 'confidence': 0.99},
        'Goods Receipt': {'support': 1.0, 'confidence': 0.98},
        'Invoice': {'support': 1.0, 'confidence': 0.97},
        'Payment': {'support': 1.0, 'confidence': 0.96},
    },
    'precedence': {
        'Invoice': {'support': 1.0, 'confidence': 0.96},
        'Goods Receipt': {'support': 1.0, 'confidence': 0.94},
        'Payment': {'support': 1.0, 'confidence': 0.92},
    },
    'succession': {
        'Order': {'support': 1.0, 'confidence': 0.99},
        'Goods Receipt': {'support': 1.0, 'confidence': 0.98},
        'Invoice': {'support': 1.0, 'confidence': 0.97},
        'Payment': {'support': 1.0, 'confidence': 0.96},
    },
    'altresponse': {},
    'altprecedence': {},
    'altsuccession': {},
    'chainresponse': {},
    'chainprecedence': {},
    'chainsuccession': {},
    'noncoexistence': {},
    'nonsuccession': {},
    'nonchainsuccession': {},
}
```

**Explanation:**

This model defines declarative constraints for a simplified Purchase-to-Pay process. 

* **Existence:** Ensures that activities like 'Order', 'Invoice', 'Payment', and 'Goods Receipt' occur at least once in a trace.
* **Absence:**  Currently empty, as there are no activities explicitly stated to never occur.
* **Exactly One:** Currently empty, as there are no activities that should occur exactly once.
* **Initialization:**  States that the process always begins with an 'Order' activity.
* **Responded Existence, Coexistence, Response, Precedence, Succession:** These constraints define the order and relationships between activities. For example, 'Response' indicates that if an 'Order' occurs, then 'Goods Receipt' and 'Invoice' will also occur later in the trace.
* **Other Constraints:** The remaining constraints (alternate response, alternate precedence, etc.) are currently empty, as they are not explicitly needed for this simplified model. 

**Note:**

* The `support` and `confidence` values are set to 1.0 for all constraints as placeholders. In a real-world scenario, these values would be calculated based on the actual process data.
* This model can be further refined and extended to include more complex relationships and constraints based on the specific requirements of the Purchase-to-Pay process.



