[DOC] Tokenizers - Classic

_analyzers/tokenizers/classic.md

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+---
+layout: default
+title: Classic
+parent: Tokenizers
+nav_order: 35
+
+---
+
+# Classic tokenizer
+
+The `classic` tokenizer parses text, applying English language grammatical rules to break the text into tokens. It includes specific logic to handle patterns such as the following:
+
+- Acronyms 
+- Email addresses
+- Domain names
+- Certain types of punctuation
+
+This tokenizer works best with the English language. It may not produce optimal results for other languages, especially those with different grammatical structures.
+{: .note}
+
+The `classic` tokenizer parses text as follows:
+
+- **Punctuation**: Splits text on most punctuation marks and removes punctuation characters. Dots that aren't followed by spaces are treated as part of the token.
+- **Hyphens**: Splits words at hyphens, except when a number is present. When a number is present in a token, the token is not split and is treated like a product number. 
+- **Email**: Recognizes email addresses and hostnames and keeps them as single tokens.
+
+## Example usage
+
+The following example request creates a new index named `my_index` and configures an analyzer with a `classic` tokenizer:
+
+```json
+PUT /my_index
+{
+  "settings": {
+    "analysis": {
+      "analyzer": {
+        "my_classic_analyzer": {
+          "type": "custom",
+          "tokenizer": "classic"
+        }
+      }
+    }
+  },
+  "mappings": {
+    "properties": {
+      "content": {
+        "type": "text",
+        "analyzer": "my_classic_analyzer"
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+POST /my_index/_analyze
+{
+  "analyzer": "my_classic_analyzer",
+  "text": "For product AB3423, visit X&Y at example.com, email info@example.com, or call the operator's phone number 1-800-555-1234. P.S. 你好."
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {
+      "token": "For",
+      "start_offset": 0,
+      "end_offset": 3,
+      "type": "<ALPHANUM>",
+      "position": 0
+    },
+    {
+      "token": "product",
+      "start_offset": 4,
+      "end_offset": 11,
+      "type": "<ALPHANUM>",
+      "position": 1
+    },
+    {
+      "token": "AB3423",
+      "start_offset": 12,
+      "end_offset": 18,
+      "type": "<ALPHANUM>",
+      "position": 2
+    },
+    {
+      "token": "visit",
+      "start_offset": 20,
+      "end_offset": 25,
+      "type": "<ALPHANUM>",
+      "position": 3
+    },
+    {
+      "token": "X&Y",
+      "start_offset": 26,
+      "end_offset": 29,
+      "type": "<COMPANY>",
+      "position": 4
+    },
+    {
+      "token": "at",
+      "start_offset": 30,
+      "end_offset": 32,
+      "type": "<ALPHANUM>",
+      "position": 5
+    },
+    {
+      "token": "example.com",
+      "start_offset": 33,
+      "end_offset": 44,
+      "type": "<HOST>",
+      "position": 6
+    },
+    {
+      "token": "email",
+      "start_offset": 46,
+      "end_offset": 51,
+      "type": "<ALPHANUM>",
+      "position": 7
+    },
+    {
+      "token": "info@example.com",
+      "start_offset": 52,
+      "end_offset": 68,
+      "type": "<EMAIL>",
+      "position": 8
+    },
+    {
+      "token": "or",
+      "start_offset": 70,
+      "end_offset": 72,
+      "type": "<ALPHANUM>",
+      "position": 9
+    },
+    {
+      "token": "call",
+      "start_offset": 73,
+      "end_offset": 77,
+      "type": "<ALPHANUM>",
+      "position": 10
+    },
+    {
+      "token": "the",
+      "start_offset": 78,
+      "end_offset": 81,
+      "type": "<ALPHANUM>",
+      "position": 11
+    },
+    {
+      "token": "operator's",
+      "start_offset": 82,
+      "end_offset": 92,
+      "type": "<APOSTROPHE>",
+      "position": 12
+    },
+    {
+      "token": "phone",
+      "start_offset": 93,
+      "end_offset": 98,
+      "type": "<ALPHANUM>",
+      "position": 13
+    },
+    {
+      "token": "number",
+      "start_offset": 99,
+      "end_offset": 105,
+      "type": "<ALPHANUM>",
+      "position": 14
+    },
+    {
+      "token": "1-800-555-1234",
+      "start_offset": 106,
+      "end_offset": 120,
+      "type": "<NUM>",
+      "position": 15
+    },
+    {
+      "token": "P.S.",
+      "start_offset": 122,
+      "end_offset": 126,
+      "type": "<ACRONYM>",
+      "position": 16
+    },
+    {
+      "token": "你",
+      "start_offset": 127,
+      "end_offset": 128,
+      "type": "<CJ>",
+      "position": 17
+    },
+    {
+      "token": "好",
+      "start_offset": 128,
+      "end_offset": 129,
+      "type": "<CJ>",
+      "position": 18
+    }
+  ]
+}
+```
+
+## Token types
+
+The `classic` tokenizer produces the following token types.
+
+| Token type    | Description  | 
+| :--- | :--- | 
+| `<ALPHANUM>`  | Alphanumeric tokens consisting of letters, numbers, or a combination of both.                     | 
+| `<APOSTROPHE>`| Tokens containing an apostrophe, commonly used in possessives or contractions (for example, `John's`).   |
+| `<ACRONYM>`   | Acronyms or abbreviations, often identified by a trailing period (for example, `P.S.` or `U.S.A.`).     |
+| `<COMPANY>`   | Tokens representing company names (for example, `X&Y`). If these tokens aren't produced automatically, you may need custom configurations or filters.  | 
+| `<EMAIL>`     | Tokens matching email addresses, containing an `@` symbol and a domain (for example,`support@widgets.co` or `info@example.com`). |
+| `<HOST>`      | Tokens matching website or host names, often containing `www.` or a domain suffix like `.com` (for example, `www.example.com` or `example.org`).  |
+| `<NUM>`       | Tokens containing only numbers or numeric-like sequences (for example, `1-800`, `12345`, or `3.14`).     |
+| `<CJ>`        | Tokens representing Chinese or Japanese characters.   |
+| `<ACRONYM_DEP>` | Deprecated acronym handling (for example, acronyms with different parsing rules in older versions). Rarely used---exists primarily for backward compatibility with legacy tokenizer rules. |