AnnotationSet like the name suggests is a set of Annotations - an extension of Set<Annotation>. we talk of annotation in the next page - they are markups of the document implemented as an object with annotation type, start and end offsets and features.

Annotation Set

Annotation sets can be managed (create, delete, modified…) by the Document they belong to.

PrintOut of an AnnotationSet

{
Original markups=
[AnnotationImpl: id=0; type=html; features={lang=en}; start=NodeImpl: id=0; offset=0; end=NodeImpl: id=1; offset=2914
, AnnotationImpl: id=1; type=head; features={}; start=NodeImpl: id=0; offset=0; end=NodeImpl: id=2; offset=25
, AnnotationImpl: id=2; type=meta; features={http-equiv=Content-Type, content=text/html; charset=UTF-8}; start=NodeImpl: id=0; offset=0; end=NodeImpl: id=0; offset=0
, AnnotationImpl: id=3; type=title; features={}; start=NodeImpl: id=0; offset=0; end=NodeImpl: id=3; offset=23
....]
}

API Signature

Access Nodes in the set

// Get the node with the smallest offset.
public Node firstNode();
// Get the node with the largest offset.
public Node lastNode();
// Get Node with the next in the set relative to `node` provided.
public Node nextNode(Node node)

New Annotations

//creating and adding a new annotation to a set  
public Integer add(Long startOffset, Long endOffset, String type, FeatureMap features);

//creating and adding a new annotation to a set   
public Integer add(Node start, Node end, String type, FeatureMap features);

//e.g.
outputAS.add(start, end, "newAnnotationType", features);

Getting Annotations by offsets

//Get annotations starting from
public AnnotationSet get(Long offset);

//Get all annotations that overlap/are between two offsets
public AnnotationSet get(Long startOffset, Long endOffset);

// Get all annotations within an interval.
public AnnotationSet getContained(Long startOffset, Long endOffset);

// Get all annotations covering an interval.
public AnnotationSet getCovering(String neededType, Long startOffset, Long endOffset);

// COMBINED CONSTRAINTS
// Get by type and feature constraints.
public AnnotationSet get(String type, FeatureMap constraints);

// Get by type, constraints and start position.
public AnnotationSet get(String type, FeatureMap constraints, Long startOffset);


// Get by type, and interval overlap.
public AnnotationSet get(String type, Long startOffset, Long endOffset);
// e.g
inputAS.get("Tokens", start, end);

// Get by type and feature presence
public AnnotationSet get(String type, Set featureNames);

// Get the set of annotation types present in the set.
Set getAllTypes()

Get Annotations in Document Order (Sort)

When you bind to and access annotationSet in the RHS their order is not guaranteed.
Here is how to order them.

  AnnotationSet annSet = tagAnnots;
  List<Annotation> verbList = gate.Utils.inDocumentOrder(annSet);
  
  //access the first annotation
  verbList.get(0);

Removing Annotations

Sometimes you want to remove annotations from a set.

public void remove(Object ann);

public boolean removeAll(Collection<?> annAS);

// example
inputAS.removeAll(annAS);

Reference
Gate NLP Tutorial

Gate Annotation Set