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

package org.apache.sis.metadata.iso.identification
Information to uniquely identify the data or service. 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 `├─` Identification «abstract» `│ ├─` Data identification `│ └─` Service identification `├─` Resolution `├─` Browse graphic `├─` Keywords `├─` Usage `├─` Aggregate information `├─` Coupled resource `├─` Operation metadata `└─` Operation chain metadata Code list `├─` Progress `├─` Keyword type `├─` Association type `├─` Initiative type `├─` Topic category `├─` Coupling type} `└─` Distributed computing platform} | Identification «abstract» `├─` Resolution `├─` Topic category «code list» `├─` Progress «code list» `├─` Browse graphic `├─` Keywords `│ └─` Keyword type «code list» `├─` Usage `└─` Associated resource `├─` Association type «code list» `└─` Initiative type «code list» Data identification Service identification `├─` Coupling type} «code list» `├─` Coupled resource `├─` Operation metadata `│ ├─` Distributed computing platform} «code list» `│ └─` Parameter descriptor `│ └─` Parameter direction} «enum» `└─` Operation chain metadata

In addition to the standard properties, SIS provides the following methods:

- `DefaultRepresentativeFraction​.setScale(double)` for computing the denominator from a scale value.

## Null values, nil objects and collections

All constructors and setter methods accept `null` arguments. A null argument value means that the metadata element can not 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

Defined in the `sis-metadata` module

- Related Packages
  Package
  Description
  org.apache.sis.metadata.iso
  Root package for ISO 19115 metadata about resources (data or services).
- Classes
  Class
  Description
  AbstractIdentification
  Basic information required to uniquely identify a resource or resources.
  DefaultAggregateInformation
  Associated resource information.
  DefaultAssociatedResource
  Associated resource information.
  DefaultBrowseGraphic
  Graphic that provides an illustration of the dataset (should include a legend for the graphic).
  DefaultCoupledResource
  Links a given operation name with a resource identified by an "identifier".
  DefaultDataIdentification
  Information required to identify a dataset.
  DefaultKeywordClass
  Specification of a class to categorize keywords in a domain-specific vocabulary that has a binding to a formal ontology.
  DefaultKeywords
  Keywords, their type and reference source.
  DefaultOperationChainMetadata
  Operation chain information.
  DefaultOperationMetadata
  Parameter information.
  DefaultRepresentativeFraction
  A scale defined as the inverse of a denominator.
  DefaultResolution
  Level of detail expressed as a scale factor or a ground distance.
  DefaultServiceIdentification
  Identification of capabilities which a service provider makes available to a service user through a set of interfaces that define a behaviour.
  DefaultUsage
  Brief description of ways in which the resource(s) is/are currently or has been used.