added VA documentation

Author: xtsoukala

docs/assets/images/virtual_assistant_1.png

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+---
+layout: default
+title: Virtual Assistant Documentation
+permalink: /virtual-assistant/
+---
+
+# Virtual Assistant Documentation
+
+The **DT4H Virtual Assistant (VA)** is a tool designed to support clinical researchers in cardiology and related fields. It enables researchers to interact in seven languages for the following tasks:
+
+- Search for and explore studies, cohorts, and patient datasets  
+- Request and retrieve metadata before starting deeper exploration  
+- Ask targeted questions regarding study characteristics, patient cohorts, or hospital nodes  
+- Perform metadata requests in a federated way using a Secure Multi-Party Computation (SMPC) algorithm, ensuring data privacy and compliance with EU standards  
+
+> **Note:** Metadata retrieval may take several minutes due to the distributed computation across nodes. It is recommended to request metadata at the beginning of a session.
+
+All chat history with the VA is automatically stored. Researchers can browse previous conversations at any time, and they have the option to delete or export them.
+
+---
+
+## Supported Languages
+
+The VA supports interaction in 7 languages, selectable from the top-right menu:
+
+- English  
+- Español (Spanish)  
+- Svenska (Swedish)  
+- Nederlands (Dutch)  
+- Italiano (Italian)  
+- Română (Romanian)  
+- Čeština (Czech)  
+
+Researchers can seamlessly switch between languages during interaction, ensuring accessibility across the European research community.
+
+![Language Selection in the VA](assets/images/virtual_assistant_1.png)  
+*Language selection in the VA*
+
+---
+
+## Main Features
+
+### Study Search and Exploration
+
+Researchers can use the VA to look for studies with specific patient characteristics, such as chronic kidney disease (CKD). Once a study of interest is identified, the VA also provides detailed information about the hospitals (nodes) that are included in the study. The results are retrieved from the **Data Catalogue (DC)**, which displays the relevant datasets together with their associated attributes.
+
+![VA chat example for study search](assets/images/virtual_assistant_2.png)  
+*Example of study search in the VA (part 2)*
+
+---
+
+### Metadata Request (Federated Step)
+
+Before starting a conversation, researchers can request cohort metadata. This step runs a secure computation across all selected nodes using the SMPC algorithm.
+
+**Steps:**  
+1. Select *Request cohort metadata* from the left-hand menu and **Create new request**  
+2. Choose the dataset name (e.g., `study1`)  
+3. Select the (hospital) nodes to include (e.g., GEM, AUMC)  
+4. Click **Create**  
+
+> **Note:** This step may take several minutes to complete. The status of the metadata request is shown (e.g., running, exited).
+
+![List of aggregated metadata requests](assets/images/virtual_assistant_3_1.png)  
+*Overview of aggregated metadata requests*
+
+![Form to start a new metadata request](assets/images/virtual_assistant_3_2.png)  
+*Creating a new metadata request for a specific study and nodes*
+
+---
+
+### Conversation with the VA
+
+Once metadata is available, researchers can:  
+- Ask questions about patient characteristics (e.g., CKD, heart failure)  
+- Retrieve key statistics from the datasets  
+- Use data visualization tools for insights  
+
+The VA ensures results are based on privacy-preserving federated queries across distributed hospital nodes.