Multitenancy is a requisite aiming to provide isolation of the different users of the cloud system, that:Prevent a tenant to access data of another tenant.Excludes to share resources between different tenants, even if they will.Involves lighter security constrains.Excludes automatic service provisioning.

Multitenancy is a fundamental requirement in cloud computing that aims to provide isolation between different users (tenants) of the cloud system. Here's a step-by-step explanation of the points you mentioned:

1. Prevent a tenant to access data of another tenant: This is true. In a multitenant architecture, each tenant's data is isolated from others. Even though they are using the same system or application, one tenant cannot access another's data. This is crucial for privacy and security.

2. Excludes to share resources between different tenants, even if they will: This is partially true. While tenants do share the same resources (like storage, RAM, CPU etc.), they are logically isolated. This means that while the physical resources are shared, each tenant operates in their own environment and cannot access or interfere with others.

3. Involves lighter security constraints: This is not true. Multitenancy does not mean lighter security constraints. In fact, it often involves more stringent security measures because the system needs to ensure data privacy and isolation for each tenant.

4. Excludes automatic service provisioning: This is not true. Multitenancy often involves automatic service provisioning. This means that when a new tenant is added, the necessary resources and services can be automatically allocated and configured for them. This is one of the benefits of cloud computing and multitenancy, as it allows for easy scalability and management.