Degree of Structuring in business process management architectures:

If the business process model prescribes the activities and their execution
constraints in a complete fashion, then the process is structured. The different
options for decisions that will be made during the enactment of the process
have been defined at design time. For instance, a credit request process might
use a threshold amount to decide whether a simple or a complex credit check
is required, for instance, 5000 euros. Each process instance then uses the
requested amount to decide on the branch to take.
Leymann and Roller have organized business processes according to dimensions
structure and repetition. They coined the term production workflow.
Production workflows are well structured and highly repetitive. Traditional
workflow management system functionality is well suited to supporting production
workflows.
If process participants who have the experience and competence to decide
on their working procedures perform business process activities, structured
processes are more of an obstacle than an asset. Skipping certain process activities
the knowledge worker does not require or executing steps concurrently
that are ordered sequentially in the process model is not possible in structured
business processes.
To better support knowledge workers, business process models can define
processes in a less rigid manner, so that activities can be executed in any order
or even multiple times until the knowledge worker decides that the goals of
these activities have been reached. So called ad hoc activities are an important
concept for supporting unstructured parts of processes.

Case handling is an approach that supports knowledge workers performing
business processes with a low level of structuring and, consequently, a high
level of flexibility. Rather than prescribing control flow constraints between
process activities, fine-grained data dependencies are used to control the enactment
of the business process.