Objects Attributes
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Introduction
All data objects in the platform have attributes. An attribute provides information (metadata) about an object. NoSQL table-item attributes in the platform are the equivalent of columns in standard NoSQL databases. See Working with NoSQL Data, including a terminology comparison. For the supported attribute data types, see the Attribute Data Types Reference.
Attribute Types
Attributes are classified into three logical types:
- User attributes
- Attributes that the user assigns to a data object using the platform APIs.
- System attributes
- Attributes that the platform automatically assigns to all objects.
The system attributes contain the object's name (
__name ) and miscellaneous information that was identified for the object by the system, such as the UID (__uid ) and GID (__gid ) of the object's owner, and the object's last-modification time__mtime_secs . For a full list of the supported system attributes, see the System-Attributes Reference. - Hidden attributes
- Attributes that the user or platform optionally assign to an object and are used to store internal information that is not meant to be exposed.
Note
The platform's naming convention is to prefix the names of system and hidden attributes with two underscores (
__) to differentiate them from user attributes.Attribute Names
Attribute names are subject to the general file-system naming restrictions and the following additional restrictions:
-
Contain only the following characters:
- Alphanumeric characters (a–z, A–Z, 0–9)
- Underscores (_)
-
Begin either with a letter (a–z, A–Z) or with an underscore (_)
-
Not identical to a reserved name — see Reserved Names
-
Length of 1–255 characters
Note
Spaces in attribute names are currently not supported.