Assignment 2 - Wan Harith Azdy bin Wan Ismail U2101138

[Wan2729]

1. Overview of the change

Addressed Component

org.openhab.core.io.rest.core

Files Modified

File	Purpose	Changes Made
ItemResource.java	Acts as the main REST API endpoint controller for managing Items, including retrieving states, updating metadata, and modifying tags.	1. Added validation to check if a tag exists before adding it. 2. Added a new function to handle adding multiple tags in a single request.

2. Call Graph

3. Impact Analysis

Impacted Component

Component	Impact Level	Description
ItemResource	High	Modified REST behavior and new endpoint
GenericItem	Medium	Tag addition invoked more frequently
ManagedItemProvider	Medium	Update operations now conditional
Logging subsystem	Low	Additional info/warn logs
REST clients	Medium	New response semantics

Behavioural Impact

Positive Impacts

• Improved correctness: Ensures tag addition actually succeeded.
• Better REST compliance: Uses 304 NOT_MODIFIED appropriately for existing tags.
• Enhanced observability: Logging aids debugging and monitoring.
• Scalability: Batch tag API reduces network calls.

Potential Risks

• Slight performance overhead: Due to extra hasTag() checks.
• REST client compatibility: Clients expecting unconditional 200 OK may need adaptation.
• Increased logging: Higher volume under high-frequency updates.