# Package org.apache.sis.metadata.iso.constraint

package org.apache.sis.metadata.iso.constraint
Information about legal and security constraints placed on data. An explanation for this package is provided in the OpenGIS® javadoc. The remaining discussion on this page is specific to the SIS implementation.

## Overview

For a global overview of metadata in SIS, see the `org​.apache​.sis​.metadata` package javadoc.

Package overview
Class hierarchy | Aggregation hierarchy
--- | ---
ISO 19115 metadata `├─` Constraints `│ ├─` Legal constraints `│ └─` Security constraints `└─` Releasability Code list `├─` Restriction `└─` Classification | Constraints `└─` Releasability Legal constraints `└─` Restriction «code list» Security constraints `└─` Classification «code list»

## Null values, nil objects and collections

All constructors and setter methods accept `null` arguments. A null argument value means that the metadata element cannot be provided, and the reason for that is unspecified. Alternatively, users can specify why a metadata element is missing by providing a value created by `NilReason​.createNilObject(Class)`.

Unless otherwise noted in the Javadoc, all getter methods may return an empty collection, an empty array or `null` if the type is neither a collection or an array. Note that non-null values may be `NilObject`s.

Unless the metadata object has been marked as unmodifiable and unless otherwise noted in the Javadoc, all collections returned by getter methods are live: adding new elements in the collection modify directly the underlying metadata object.

Since:
  0.3

- Related Packages
  Package
  Description
  org.apache.sis.metadata.iso
  Root package for ISO 19115 metadata about resources (data or services).
- Classes
  Class
  Description
  DefaultConstraints
  Restrictions on the access and use of a resource or metadata.
  DefaultLegalConstraints
  Restrictions and legal prerequisites for accessing and using the resource.
  DefaultReleasability
  Information about resource release constraints.
  DefaultSecurityConstraints
  Handling restrictions imposed on the resource for national security or similar security concerns.