Definition of transparency
In scrum guide, it is said : " Significant aspects of the process must be visible to those responsible for the outcome.
Transparency requires those aspects be defined by a common standard so observers share a common understanding of what is being seen.
For example:
A common language referring to the process must be shared by all participants;"
why authors used process and not framework. Scrum is defined as a framework.
And does the word aspect refers to roles, events, artifacts and rules.
The section you quote is describing how empirical process control is implemented. Transparency is one of the three legs of this, along with inspection and adaptation. Scrum is sometimes referred to as a process framework.