Some entities need to match patterns rather than specific terms. For example, national identification numbers, IDs, license plates, and so on. With *regexp entities* , you can provide [regular expressions](https://github.com/google/re2/wiki/Syntax) for matching. ## Compound regular expressions Each regexp entity corresponds to a single pattern, but you can provide multiple regular expressions if they all represent variations of a single pattern. During agent training, all regular expressions of a single entity are combined with the alternation operator (`|`) to form one *compound regular expression*. For example, if you provide the following regular expressions for a phone number: - `^[2-9]\d{2}-\d{3}-\d{4}$` - `^(1?(-?\d{3})-?)?(\d{3})(-?\d{4})$` The compound regular expression becomes: - `^[2-9]\d{2}-\d{3}-\d{4}$|^(1?(-?\d{3})-?)?(\d{3})(-?\d{4})$` The ordering of regular expressions matters. Each of the regular expressions in the compound regular expression are processed in order. Searching stops once a valid match is found. For example, for an end user expression of "Seattle": - `Sea|Seattle` matches "Sea" - `Seattle|Sea` matches "Seattle" ## Special handling for speech recognition > [!NOTE] > **Note:** Enabling [auto speech adaptation](https://docs.cloud.google.com/dialogflow/cx/docs/concept/speech-adaptation) is recommended when using regexp entities. Also see the speech adaptation [regexp-specific guidelines](https://docs.cloud.google.com/dialogflow/cx/docs/concept/speech-adaptation#regexp-entities). If your agent uses speech recognition (also known as audio input, speech-to-text, or STT), your regular expressions will need special handling when matching letters and numbers. A spoken end-user utterance is first processed by the speech recognizer before entities are matched. When an utterance contains a series of letters or numbers, the recognizer may pad each character with spaces. In addition, the recognizer may interpret digits in word form. For example, an end-user utterance of "My ID is 123" may be recognized as any of the following: - "My ID is 123" - "My ID is 1 2 3" - "My ID is one two three" To accommodate three digit numbers, you could use the following regular expressions: ``` \d{3} ``` ``` \d \d \d ``` ``` (zero|one|two|three|four|five|six|seven|eight|nine) (zero|one|two|three|four|five|six|seven|eight|nine) (zero|one|two|three|four|five|six|seven|eight|nine) ``` ## Create a regexp entity ### Console 1. Open the [Dialogflow CX console](https://dialogflow.cloud.google.com/cx/projects). 2. Choose your GCP project. 3. Select your agent. 4. Select the **Manage** tab. 5. Click **Entity Types**. 6. Click **Create**. 7. Check **Regexp entities**. 8. Complete remaining fields. 9. Click **Save**. ### API Set the `EntityType.kind` field to `KIND_REGEXP`. **Select a protocol and version for the EntityType reference:** | Protocol | V3 | V3beta1 | |---|---|---| | REST | [EntityType resource](https://docs.cloud.google.com/dialogflow/cx/docs/reference/rest/v3/projects.locations.agents.entityTypes) | [EntityType resource](https://docs.cloud.google.com/dialogflow/cx/docs/reference/rest/v3beta1/projects.locations.agents.entityTypes) | | RPC | [EntityType interface](https://docs.cloud.google.com/dialogflow/cx/docs/reference/rpc/google.cloud.dialogflow.cx.v3#google.cloud.dialogflow.cx.v3.EntityTypes) | [EntityType interface](https://docs.cloud.google.com/dialogflow/cx/docs/reference/rpc/google.cloud.dialogflow.cx.v3beta1#google.cloud.dialogflow.cx.v3beta1.EntityTypes) | | C++ | [EntityTypesClient](https://googleapis.dev/cpp/google-cloud-dialogflow_cx/latest/classgoogle_1_1cloud_1_1dialogflow__cx_1_1EntityTypesClient.html) | Not available | | C# | [EntityTypesClient](https://docs.cloud.google.com/dotnet/docs/reference/Google.Cloud.Dialogflow.Cx.V3/latest/Google.Cloud.Dialogflow.Cx.V3.EntityTypesClient) | Not available | | Go | [EntityTypesClient](https://docs.cloud.google.com/go/docs/reference/cloud.google.com/go/dialogflow/latest/cx/apiv3#cloud_google_com_go_dialogflow_cx_apiv3_EntityTypesClient) | Not available | | Java | [EntityTypesClient](https://docs.cloud.google.com/java/docs/reference/google-cloud-dialogflow-cx/latest/com.google.cloud.dialogflow.cx.v3.EntityTypesClient) | [EntityTypesClient](https://docs.cloud.google.com/java/docs/reference/google-cloud-dialogflow-cx/latest/com.google.cloud.dialogflow.cx.v3beta1.EntityTypesClient) | | Node.js | [EntityTypesClient](https://googleapis.dev/nodejs/dialogflow-cx/latest/v3.EntityTypesClient.html) | [EntityTypesClient](https://googleapis.dev/nodejs/dialogflow-cx/latest/v3beta1.EntityTypesClient.html) | | PHP | Not available | Not available | | Python | [EntityTypesClient](https://docs.cloud.google.com/python/docs/reference/dialogflow-cx/latest/google.cloud.dialogflowcx_v3.services.entity_types.EntityTypesClient) | [EntityTypesClient](https://docs.cloud.google.com/python/docs/reference/dialogflow-cx/latest/google.cloud.dialogflowcx_v3beta1.services.entity_types.EntityTypesClient) | | Ruby | Not available | Not available |
## Limitations The following limitations apply: - [Fuzzy matching](https://docs.cloud.google.com/dialogflow/cx/docs/concept/entity-fuzzy) cannot be enabled for regexp entities. These features are mutually exclusive. - Each agent can have a maximum of 50 regexp entities. - The [compound regular expression](https://docs.cloud.google.com/dialogflow/cx/docs/concept/entity-regexp#compound) for an entity has a maximum length of 2000 characters.