# Access Control System Resources The Seam ACS schema consists of a series of resources. These resources interact intuitively, enabling you to manage your ACS in a logical, efficient manner. Seam's universal API provides the flexibility to manage a variety of [ACSs](https://docs.seam.co/latest/capability-guides/access-systems/connect-an-acs-to-seam/understanding-access-control-system-differences), each of which may have manufacturer-specific differences. For details about your ACS, see the corresponding [system integration guide](https://docs.seam.co/latest/device-and-system-integration-guides/overview#access-control-systems). The following diagram shows an example of one ACS, including the ACS resources and the relationships between them:

Seam's ACS resources provide the flexibility to manage your ACS intuitively, regardless of the differences between various ACS manufacturers.

The following table provides a brief description of each of the Seam ACS resources:

ACS Resource	Description
`acs_system`	The top-level object. Represents one or more buildings, residential locations, or other sites that you manage using this ACS. For more information, see Retrieving ACS System Details.
`acs_user`	The set of users who access the entrances. If you manage multiple ACSs and need to grant the same user access to entrances in multiple ACSs, you can also use Seam user identities. With user identities, you can link an application user in your own system to one or more Seam ACS users. For more information, see Managing ACS Users.
`acs_access_group`	Some ACSs use access groups as an efficient way to grant sets of scheduled entrance access to one or more users. For more information, see Assigning ACS Users to Access Groups.
`acs_credential`	A digital means that authorizes a user to access one or more entrances at specific days and times. Examples of credentials include RFID cards, mobile keys, and PIN codes. For more information, see Managing Credentials.
`acs_entrance`	The set of entrances, doors, or zones that you want to manage. You identify each entrance by the corresponding lock object. For more information, see Retrieving Entrance Details.

{% hint style="info" %} You configure the access schedules for your ACS users either through access groups or credentials, depending on your specific ACS. There is no separate schedule resource in the Seam API. {% endhint %}