This code system http://terminology.hl7.org/CodeSystem/goal-relationship-type defines the following codes:

CodeDisplayDefinition
predecessor PredecessorIndicates that the target goal is one which must be met before striving for the current goal.
successor SuccessorIndicates that the target goal is a desired objective once the current goal is met.
replacement ReplacementIndicates that this goal has been replaced by the target goal.
milestone MilestoneIndicates that the target goal is considered to be a "piece" of attaining this goal.
other OtherIndicates that the relationship is not covered by one of the pre-defined codes. (An extension may convey more information about the meaning of the relationship.).
<status value="draft"/> <experimental value="false"/> <date value="2020-04-09T21:10:28+00:00"/> <publisher value="HL7 (FHIR Project)"/> <contact> <telecom> <system value="url"/> <value value="http://hl7.org/fhir"/> </telecom> <telecom> <system value="email"/> <value value="fhir@lists.hl7.org"/> </telecom> </contact> <description value="Types of relationships between two goals."/> <caseSensitive value="true"/> <valueSet value="http://terminology.hl7.org/ValueSet/goal-relationship-type"/> <content value="complete"/> <concept> <code value="predecessor"/> <display value="Predecessor"/> <definition value="Indicates that the target goal is one which must be met before striving for the current goal."/> </concept> <concept> <code value="successor"/> <display value="Successor"/> <definition value="Indicates that the target goal is a desired objective once the current goal is met."/> </concept> <concept> <code value="replacement"/> <display value="Replacement"/> <definition value="Indicates that this goal has been replaced by the target goal."/> </concept> <concept> <code value="milestone"/> <display value="Milestone"/> <definition value="Indicates that the target goal is considered to be a "piece" of attaining this goal."/> </concept> <concept> <code value="other"/> <display value="Other"/> <definition value="Indicates that the relationship is not covered by one of the pre-defined codes. (An extension may convey more information about the meaning of the relationship.)."/> </concept> </CodeSystem>