# Sample Use Cases for Process Runtime REST API
A **Custom Application** is an external application developed outside the ONEWEB platform that follows a company’s business requirements.\
Such applications can interact with ONEWEB **Process Runtime** using **Process Runtime REST APIs** to **start, control, and complete business processes**.
Using these APIs, developers can orchestrate workflows end‑to‑end from external systems (web, mobile, or third‑party applications).
***
### Use Case Overview
**Use Case:**\
A Custom Application controls a **Room Booking** business process hosted in ONEWEB.
The Custom App:
* Starts the booking process
* Retrieves runtime tasks
* Assigns tasks to users
* Allows users to claim, unclaim, and complete tasks
* Drives the process until completion
***
### Example Process: *Booking Room*
The following process illustrates a typical **Booking Room** workflow:
* User selects a room
* System checks booking status
* If the room is already booked → user selects another room
* If the room is available → customer details are entered
* Booking is saved to the database
* Room status is updated
* Process continues until completion
This process is fully controlled from a **Custom App** using REST APIs.
***
### Step‑by‑Step: Controlling Process via REST API
***
#### Step 1: Start the Process Flow
The Custom App starts the process by calling the **Start Process API**.
* Input parameters are passed as JSON
* In this example, the parameters are:
* `RoomObject`
* `CustomerInfo`
**Result:**
* The system starts a new process instance
* A unique **Instance ID** is returned (e.g.\
`122056879-85735849-0b71-4299-9cd2-165f5b31c12e`)
This Instance ID is required to control subsequent steps.
***
#### Step 2: Retrieve Task Using Instance ID
Using the **Instance ID**, the developer retrieves the current task(s) of the process.
* API: `Get task by instance ID`
* The system returns:
* Task ID
* Task name
* Task metadata
The **Task ID** will be used for assignment and completion.
***
#### Step 3: Assign Task to User
Once the Task ID is known, the Custom App assigns the task to a user.
**Example API Call:**
```
http://192.168.0.213:8080/BPMREST/service/runtime/tasks/
122056910-494baede-088f-46bb-8a24-77b049ef996c
/assign?user=origcmr4
```
**Result:**
* The task appears in the **To‑Do List** of user `origcmr4`
***
#### Alternative Task Assignment Method
Tasks can also be assigned **directly using the Instance ID**:
```
http://192.168.0.213:8080/BPMREST/service/runtime/instance/
122056879-85735849-0b71-4299-9cd2-165f5b31c12e
/tasks/assign?user=origcmr4
```
This assigns all active tasks in the process instance to the user.
***
#### Step 4: Claim / Unclaim / Complete Task
The assigned user can now control the task lifecycle.
**Claim Task**
```
.../tasks/{taskId}/claim?user=origcmr4
```
**Unclaim Task**
```
.../tasks/{taskId}/claim?user=
```
**Complete Task**
```
.../tasks/{taskId}/complete?user=origcmr4
```
After **Complete** is called:
* The task is finished
* The process automatically moves to the **next activity**
* The workflow continues based on process configuration
***
### End‑to‑End Integration Pattern
From a Custom App, the full process control pattern is:
1. Start process
2. Receive Instance ID
3. Retrieve tasks
4. Assign task(s)
5. Claim and complete tasks
6. Continue until End Event
This enables complete **external orchestration of business workflows**.
***
### Summary
This example demonstrates how a **Custom Application** can fully control a ONEWEB **Process Flow** using **Process Runtime REST APIs**.
With these APIs, external systems can:
* Start business processes
* Track and manage process instances
* Assign, claim, and complete human tasks
* Drive workflows end‑to‑end without ONEWEB UI
The **Process Runtime REST API** is essential for integrating ONEWEB BPM capabilities into **enterprise systems, portals, mobile apps, and third‑party platforms**.
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