In the realm of Petri net theory, one might propose:

### Opposite Conception
* **Forever Place (or Sink Place)**: As an opposite to a "Source Place", which serves the purpose of providing initial marking or resources, a "Forever Place" or "Sink Place" acts to consume resources. It is akin to a "remove" or "sink" mechanism within a system. All transitions that can fire directly from or directly to this place are considered "sink" or "removal" transitions, effectively reducing the system's resources.

### More General Concept
* **Cross-Active (or Hybrid) Petri Nets**: This concept encompasses both Petri nets and Automatic Control Models (flexibly encompassing Markov chains, Dynamic Programming, etc.), thus providing an overarching framework which accommodates different types of diagrammatic models such as activity / information flow nets, decision net diagrams, Hierarchical Petri nets, Interactive Petri nets, model transformations, Process Algebra Equations (PAE), Quantized nets, and Real-time/Clock nets.

### Explanation
* **Forever Place / Sink Place**: Unlike a source place that replenishes the system with resources, a "Forever Place" or sink place represents the consumption or depletion of resources within a modelled system. By drawing boundaries around such places, it helps in pinning down the dynamic flow and possible depletion mechanisms of resources or items across the system. Transition fire as usual, but any changes made entering this "sink" place can be tracked to understand how the resources are being managed or potentially exhausted within the system's lifecycle.

* **Cross-Active (more general) Petri Nets**: This archetypal framework encompasses Petri nets to an extent while accommodating a broader category of sequential process-induction models like Control Models, Dynamic Programming, Markov chains, etc. This type of model would have elements of standard Petri nets alongside those found in control flow diagrams, decision making diagrams (like decision nets), process algebra (such as activity flow, interactive behavior, or hierarchical composition), and system transformation processes. By binding the diagrammatic language, activities, and decisions into a common underlying formal structure, models of all these diverse types could communicate effectively. They could analyze or compare the cost-effectiveness (like in dynamic programming), the interaction between concurrent activities (activity/interaction nets), or the control flow with inherent computation (decision/flow nets). This standardised approach helps in unification of complex system IM and modeling tasks, making way for a versatile approach in system modelling and