Here's a DECLARE model for a hypothetical Purchase-to-Pay process. I've assumed some activities and created constraints based on common process flows. I've set the support to 1.0 as requested.

```python
declare_model = {
    'existence': {
        'Receive Purchase Request': {'support': 1.0, 'confidence': 1.0},
        'Approve Purchase Request': {'support': 1.0, 'confidence': 1.0},
        'Create Purchase Order': {'support': 1.0, 'confidence': 1.0},
        'Receive Goods/Services': {'support': 1.0, 'confidence': 1.0},
        'Create Invoice': {'support': 1.0, 'confidence': 1.0},
        'Match Purchase Order with Invoice': {'support': 1.0, 'confidence': 1.0},
        'Approve Invoice': {'support': 1.0, 'confidence': 1.0},
        'Process Payment': {'support': 1.0, 'confidence': 1.0},
        'Archive Records': {'support': 1.0, 'confidence': 1.0}
    },
    'absence': {},
    'exactly_one': {
        'Approve Purchase Request': {'support': 1.0, 'confidence': 1.0},
        'Approve Invoice': {'support': 1.0, 'confidence': 1.0}
    },
    'init': {
        'Receive Purchase Request': {'support': 1.0, 'confidence': 1.0}
    },
    'responded_existence': {},
    'coexistence': {},
    'response': {
        ('Receive Goods/Services', 'Create Invoice'): {'support': 1.0, 'confidence': 1.0}
    },
    'precedence': {
        ('Approve Purchase Request', 'Create Purchase Order'): {'support': 1.0, 'confidence': 1.0},
        ('Receive Goods/Services', 'Match Purchase Order with Invoice'): {'support': 1.0, 'confidence': 1.0}
    },
    'succession': {
        ('Create Purchase Order', 'Receive Goods/Services'): {'support': 1.0, 'confidence': 1.0},
        ('Match Purchase Order with Invoice', 'Approve Invoice'): {'support': 1.0, 'confidence': 1.0},
        ('Approve Invoice', 'Process Payment'): {'support': 1.0, 'confidence': 1.0}
    },
    'altresponse': {},
    'altprecedence': {},
    'altsuccession': {},
    'chainresponse': {},
    'chainprecedence': {},
    'chainsuccession': {},
    'noncoexistence': {},
    'nonsuccession': {},
    'nonchainsuccession': {}
}
```

This model assumes that:

1. The process starts with receiving a purchase request.
2. After approving the purchase request, a purchase order is created.
3. After receiving goods/services, an invoice is created.
4. After matching the purchase order with the invoice, the invoice is approved.
5. After approving the invoice, the payment is processed.
6. Finally, the records are archived.

Some constraints, like `responded_existence`, `coexistence`, `altresponse`, `altprecedence`, `altsuccession`, `chainresponse`, `chainprecedence`, `chainsuccession`, `noncoexistence`, `nonsuccession`, and `nonchainsuccession`, are not used in this model, as they are not necessary to describe the given process flow.