Update data structure related to Tree

yorkie-team · Aug 25, 2023 · a3170de · a3170de · github-actions · Aug 25, 2023
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diff --git a/design/data-structure.md b/design/data-structure.md
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 ---
 title: data-structure
-target-version: 0.3.1
+target-version: 0.4.6
 ---
 
 # Data Structures
@@ -28,7 +28,9 @@ The `json` and `crdt` package has data structures for representing the contents
 
 Below is the dependency graph of data structures used in a JSON-like document.
 
-![data-structure](./media/data-structure.png)
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+<img src="https://github.com/yorkie-team/yorkie/assets/78714820/d91aebad-4637-4873-803e-cda025ade1f6" width="700" />
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 The data structures can be divided into three groups:
 
@@ -45,7 +47,9 @@ JSON-like data strucutres are used when editing JSON-like documents.
 - `Primitive`: represents primitive data like `string`, `number`, `boolean`, `null`, etc.
 - `Object`: represents [object type](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object) of JavaScript. Just like JavaScript, you can use `Object` as [hash table](https://en.wikipedia.org/wiki/Hash_table).
 - `Array`: represents [array type](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array) of JavaScript. You can also use `Array` as [list](https://en.wikipedia.org/wiki/List_(abstract_data_type)).
-- `Text`: represents text with style attributes in rich text editors such as [Quill](https://github.com/yorkie-team/yorkie-js-sdk/blob/main/examples/quill.html). Users can express styles such as bold, italic, and underline to text content. Of course, it can represent just a plain text in text-based editors such as [CodeMirror](https://github.com/yorkie-team/yorkie-js-sdk/blob/main/examples/index.html). It supports collaborative editing; multiple users can modify parts of the contents without conflict.
+- `Text`: represents text with style attributes in rich text editors such as [Quill](https://quilljs.com/). Users can express styles such as bold, italic, and underline to text content. Of course, it can represent just a plain text in text-based editors such as [CodeMirror](https://codemirror.net). It supports collaborative editing; multiple users can modify parts of the contents without conflict.
+- `Counter`: represents a counter in the document. As a proxy for the CRDT counter, it is used when the user manipulates the counter from the outside.
+- `Tree`: represents CRDT-based tree structure that is used to represent the document tree of text-based editor such as [ProseMirror](https://prosemirror.net/).
 
 JSON-like data structures can be edited through proxies. For example:
 
@@ -72,15 +76,16 @@ CRDT data structures are used by JSON-like group to resolve conflicts in concurr
 - `ElementRHT`: similar to `RHT`, but has elements as values.
 - `RGATreeList`: extended `RGA(Replicated Growable Array)` with an additional index tree. The index tree manages the indices of elements and provides faster access to elements at the int-based index.
 - `RGATreeSplit`: extended `RGATreeList` allowing characters to be represented as blocks rather than each single character.
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+- `CRDTTree`: represents the CRDT tree with an index tree structure'. It resolves conflicts arising from concurrent editing.
 ### Common Group
 
 Common data structures can be used for general purposes.
 
 - [`SplayTree`](https://en.wikipedia.org/wiki/Splay_tree): A tree that moves nodes to the root by splaying. This is effective when user frequently access the same location, such as text editing. We use `SplayTree` as an index tree to give each node a weight, and to quickly access the node based on the index.
 - [`LLRBTree`](https://en.wikipedia.org/wiki/Left-leaning_red%E2%80%93black_tree): A tree simpler than Red-Black Tree. Newly added `floor` method finds the node of the largest key less than or equal to the given key.
 - [`Trie`](https://en.wikipedia.org/wiki/Trie): A data structure that can quickly search for prefixes of sequence data such as strings. We use `Trie` to remove nested events when the contents of the `Document` are modified at once.
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+- `IndexTree`: A tree implementation to represent a document of text-based editors.
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 ### Risks and Mitigation
 
 We can replace the data structures with better ones for some reason, such as performance. For example, `SplayTree` used in `RGATreeList` can be replaced with [TreeList](https://commons.apache.org/proper/commons-collections/apidocs/org/apache/commons/collections4/list/TreeList.html).