Purchase order processing UML activity diagram

This purchase order processing UML activity diagram was created on the base of activity diagram from the software architecture documentation wiki of the Software Engineering Institute (SEI) of Carnegie Mellon University (CMU).
[wiki.sei.cmu.edu/ sad/ index.php/ Image:PurchaseOrderActivityDiagram.png]
"A purchase order (PO) is a commercial document and first official offer issued by a buyer to a seller, indicating types, quantities, and agreed prices for products or services. Acceptance of a purchase order by a seller forms a contract between the buyer and seller, so no contract exists until the purchase order is accepted. It is used to control the purchasing of products and services from external suppliers.
Creating a purchase order is typically the first step of the purchase to pay process in an ERP system." [Purchase order. Wikipedia]
This purchase order processing UML activity diagram example was created using the ConceptDraw PRO diagramming and vector drawing software extended with the ATM UML Diagrams solution from the Software Development area of ConceptDraw Solution Park.

This IDEF3 diagram example was redesigned from the Wikimedia Commons file: 2-02 Example of a Transition Schematic.jpg.
[commons.wikimedia.org/ wiki/ File:2-02_ Example_ of_ a_ Transition_ Schematic.jpg]
"The schematic in Figure 2-2 represents an Object Schematic for the Order Material scenario derived from the business owner’s description. This example happens to illustrate a Transition Schematic since it characterizes the nature and structure of object state transitions for occurrences of the Order Material scenario. A key document in this process is the Purchase Request form. This form is eventually transformed into a Purchase Order (PO) via the Order Material process. A circle containing the name of an object represents an object of a certain kind (e.g., Purchase Request, Account Manager, Project). These labeled circles are known as kind symbols. A certain kind of object being in a certain state is represented by a circle with a label that captures both the kind itself and a corresponding state, thereby representing the type (or class) of objects that are in that state (within a given process). ... One of the first steps to develop an Object Schematic is to identify the possible states in which the object can exist. Though a real-world object often evolves through a continuum of states, an Object Schematic focuses on those distinguished states of particular interest to the domain expert. The transition arcs (arrows with triangular, filled-in heads) connecting the circles symbolize a state transition, the activity of changing from one state to another. The conditions that establish when an object is in a given state, how it exists a state, how it can transition between states, and how it can enter a new state are recorded on a special form. The banded boxes linked to the arrows (called referents) are aids to describe the relationships between objects states and UOBs, scenarios, or other Transition Schematics that participate in a scenario occurrence. ... The transition junctions containing an “X” (for exclusive or) indicate the choice of exactly one path among several possible paths in an occurrence." [IDEF3 Process Description Capture Method Report AL-TR-1995-XXXX. idef.com/ pdf/ Idef3_ fn.pdf]
The diagram "Transition schematic - IDEF3 diagram example" was created using the ConceptDraw PRO diagramming and vector drawing software extended with the solution "IDEF Business Process Diagrams" from the area "Business Processes" of ConceptDraw Solution Park.