The input uses an attribute of this type to identify what action to perform on the specified entity: A: Add an new entity, and report an error if the entity already exists C: Change an existing entity, and report an error if the entity doesn't exist yet. AC: Change an entity or create a new one if it doesn't exist yet. This is the default. D: Delete an entity, and report an error if the entity doesn't exist. Buffers and resources are linked to a (physical or logical) location. Locations are merely used for simple association, and have no active use in the model. Demand is linked to a customer. This association currently has no active use in the model. A supplier sells material to your company. An operation defines an activity that can consume and produce material from buffers, load capacity on resources. An operation nested inside another one. This is used for operations of type routing, alternate and split. A blocked-by dependency between two operations. An item defines the products being planned, sold, stored and/or manufactured. Buffers and demands have a reference to an item. A itemsupplier specifies an item than can be procured from a supplier. A itemsupplier specifies an item than can be shipped from an origin location to a destination location. A setup matrix defines the conversion between different resource setups. A skill that can be assigned to a resource. A resource represents a workcentre, a physical or logical representation of capacity. A resourceskill specifies a skill which a certain resource has. A buffer represents a combination of a item and location. It is the entity for keeping modeling inventory. A synonym is SKU or stock-keeping-unit. A flow represent the production or consumption of material from a buffer. A flow is attached to an operation. A load links a resource to a certain operation. A demand represents a independent demand to be planned. It can represent a customer order or a forecast. A calendar is used to represent time dependent parameters. This entity represent the key for representing the plan. It models an operation planned at a certain quantity and time. This entity is used to represent inconsistencies, alerts and warnings in the model. Problems are maintained internally by the system. They are thus export-only, meaning that we can't directly import or build problems. This is the root tag in the data schema.