Web2.0

omits details that we are unable to capture at this point

Each document has an id

Each wavelet is a container for any number of documents.

Each item has a key-value map of annotations.

to represent text formatting, spelling suggestions and hyper-links

independent of the XML document structure

A document is a sequence of items

is composed of an XML document and a set of annotations.

Annotation keys and values are strings

each item conceptually has its own annotation map

more efficient to have just one annotation map for each consecutive run of items with the same annotations

current annotations update, which is a map of annotation keys to pairs (old-value, new-value), where old-value and new-value are either null or an annotation value

After the final component, the annotations update must be empty

Document operation components can be divided into four classes

do not directly affect the document or the cursor

annotation boundaries (annotationBoundary) change the current annotations update

message AnnotationBoundary { // This field is set to true if and only if both ends and changes are // empty. It is needed to ensure that the optional annotationBoundary // component field is not dropped during serialization. optional bool empty = 1; // MUST NOT have the same string twice. repeated string end = 2; // MUST NOT have two updates with the same key. MUST NOT // contain any of the strings listed in the 'end' field. repeated KeyValueUpdate change = 3; }

optional AnnotationBoundary annotationBoundary = 1; optional string characters = 2; optional ElementStart elementStart = 3; optional bool elementEnd = 4; optional int32 retainItemCount = 5; optional string deleteCharacters = 6; optional ElementStart deleteElementStart = 7; optional bool deleteElementEnd = 8; optional ReplaceAttributes replaceAttributes = 9; optional UpdateAttributes updateAttributes = 10;