Data Enquiry Access Paths
Works on LDM to see if it can satisfy the enquiries which the system will make on it data.
Uses a simplified LDM with arrows indicating the direction of the enquiry. (based on Jackson diagrams)
Procedure:.
Draw the part of the LDS needed for the enquiry. Don't include relationship labels.
For each enquiry redraw LDS:
Show access from master to detail vertically
Show access from detail to master horizontally
Convert this diagram into an Enquiry Access Path.
Remove
crow's foot
relationships connect with an Access arrow instead.
Sometimes access is to a set of details rather than a singleton, this is shown with an added box,
set of X.
If an enquiry wishes to choose entity types based on an attribute this is shown as a selection.
Mark the entry point for the enquiry and give the criteria (key or search values)
Confirm that the required data can be obtained in one of the following three ways
Read Directly using entry attributes
Read next detail from current master.
Read master from current detail