1 Introduction

The OData protocol is comprised of a set of specifications for representing and interacting with structured content. This document describes the OData Atom Format of the payload returned from an OData Service when requesting the application/atom+xml mime type.

An OData payload may represent:

a single primitive value
a sequence of primitive values
a single structured (“complex”) value
a sequence of structured (“complex”) values
an entity (a structured type with an identity)
a resource reference
a sequence of entities
a sequence of changes
a media resource
a single instance of a mime type
a single link to a related entity
a collection of links to related entities
a service document describing the collections (entity sets) exposed by the service
an xml document describing the entity model exposed by the service
an error document
a batch of requests to be executed in a single request
a set of responses returned from a batch request

For a description of the xml format for describing an entity model, see [OData-CSDL]. For a description of batch requests and responses, see [Error! Reference source not found.].

1.1 Terminology

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in [RFC2119].

1.2 Normative References

This document references the following related documents:

[GML] Portele, C., Ed., "OpenGIS Geography Markup Language (GML) Encoding", August 2007. http://portal.opengeospatial.org/files/?artifact_id=20509.

[OData-ABNF] OData ABNF Construction Rules Version 4.0.
See link in “Related work” section on cover page.

[OData-CSDL] OData Version 4.0 Part 3: Common Schema Definition Language (CSDL).
See link in “Related work” section on cover page.

[OData-MetaXML] OData Metadata XML Schema.
See link in “Additional artifacts” section on cover page.

[OData-Protocol] OData Version 4.0 Part1: Protocol.
See link in“Related work” section on cover page.

[OData-URL] OData Version 4.0 Part 2: URL Conventions.
See link in "Related work" section on cover page.

[OData-VocAtom] OData Atom Vocabulary.
See link in “Additional artifacts” section on cover page.

[RFC2119] Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels”, BCP 14, RFC 2119, March 1997. http://www.ietf.org/rfc/rfc2119.txt.

[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, “Uniform Resource Identifier (URI): Generic Syntax”, IETF RFC3986, January 2005. http://www.ietf.org/rfc/rfc3986.txt.

[RFC3987] Duerst, M. and M. Suignard, “Internationalized Resource Identifiers (IRIs)”, RFC 3987, January 2005. http://www.ietf.org/rfc/rfc3987.txt.

[RFC4287] Nottingham, M., Ed., and R. Sayre, Ed. “The Atom Syndication Format”, RFC 4287, December 2005. http://www.ietf.org/rfc/rfc4287.txt.

[RFC5023] Gregorio, J., Ed., and B. de hOra, Ed., “The Atom Publishing Protocol”, RFC 5023, October 2007. http://www.ietf.org/rfc/rfc5023.txt.

[RFC5646] Phillips, A.., Ed., and M. Davis, Ed., “Tags for Identifying Languages”, BCP 47, RFC 5646, September 2009. http://tools.ietf.org/html/rfc5646.

[RFC6721] Snell, J., "The Atom 'deleted-entry' Element", RFC 6721, September 2012, http://tools.ietf.org/html/rfc6721.

2 Atom Format Design

The Atom Syndication Format [RFC4287] defines an XML-based format for describing collections (“feeds”) made up of individual “entries”. The Atom Publishing Protocol [RFC5023] defines an application-level protocol based on HTTP transfer of Atom-formatted representations.

OData builds on [RFC4287] and [RFC5023] by defining additional conventions and extensions for representing and querying entity data.

As specified in [RFC4287] and [RFC5023] processors that encounter foreign markup MUST NOT stop processing and MUST NOT signal an error. This includes additional elements or attributes in any namespace, including elements and attributes in the OData Data and Metadata namespaces, e.g. values for properties not declared in $metadata, and annotations that are not defined in the version of the payload being returned.

2.1 Namespaces

OData defines meaning for elements and attributes defined in the following namespaces.

2.1.1 Atom Syndication

Atom elements and attributes are defined within the Atom namespace: http://www.w3.org/2005/Atom.

In this specification the namespace prefix atom is used to represent the Atom Namespace, however the prefix name is not prescriptive.

2.1.2 Atom Publishing Protocol

Atom Publishing Protocol (AtomPub) elements and attributes are defined within the AtomPub namespace: http://www.w3.org/2007/app.

In this specification the namespace prefix app is used to represent the AtomPub Namespace, however the prefix name is not prescriptive.

2.1.3 Atom Tombstone

The deleted-entry element is defined within the Atom Tombstone namespace: http://purl.org/atompub/tombstones/1.0.

In this specification the namespace prefix atom-tombstone is used to represent the Atom Tombstone Namespace, however the prefix name is not prescriptive.

2.1.4 OData Data

Elements that describe the actual data values for an entity are qualified with the OData Data Namespace: http://docs.oasis-open.org/odata/ns/data.

In this specification the namespace prefix data is used to represent the OData Data Namespace, however the prefix name is not prescriptive.

2.1.5 OData Metadata

Attributes and elements that represent metadata (such as type, null usage, and entry-level etags) are defined within the OData Metadata Namespace:

http://docs.oasis-open.org/odata/ns/metadata.

Custom elements or attributes MUST NOT use this namespace.

In this specification the namespace prefix metadata is used to represent the OData Metadata Namespace, however the prefix name is not prescriptive.

2.1.6 XML Schema Definition for OData Metadata

This specification contains a normative XML schema for the OData Metadata namespace, see [OData-MetaXML].

It only define the shape of well-formed OData metadata, but is not descriptive enough to define what correct OData metadata is. This specification document defines additional rules that correct OData metadata MUST fulfill. In case of doubt on what makes OData metadata correct the rules defined in this specification document take precedence.

3 Requesting the Atom Format

The OData Atom format MAY be requested using the $format query option in the request URL with the MIME type application/atom+xml, or the case-insensitive abbreviation atom.

Alternatively, this format MAY be requested using the Accept header with the MIME type application/atom+xml.

If specified, $format overrides any value specified in the Accept header.

The service document MAY additionally be requested with the more specific MIME type application/atomsvc+xml using either $format or Accept.

All resources MAY additionally be requested with the less specific MIME type application/xml using either $format or Accept, or the case-insensitive abbreviation xml using $format.

4 Common Characteristics

4.1 Header Content-Type

The Content-Type header for Atom responses MUST use the most specific MIME type for the requested resource that is indicated as acceptable by the client.

Requests using the $format query option with the abbreviation atom MUST receive the MIME type

· application/atomsvc+xml for the service document,

· application/atom+xml for entities and collections of entities, references, or changes,

· application/xml for all other resources.

Requests using $format or an Accept header with value application/atom+xml MUST receive the MIME type

· application/xml for the service document,

· application/atom+xml for entities and collections of entities, refereces, or changes,

· application/xml for all other resources.

Requests using $format or an Accept header with value application/xml or $format with the abbreviation xml MUST receive the MIME type application/xml for all resources.

Data modification requests for entities or collections of entities MUST specify a Content-Type header with a value of either application/atom+xml or application/xml. Data modification requests for all other resources MUST specify a Content-Type header with a value of application/xml.

Message Body

4.2 Message Body

Each message body MUST be represented as an XML document with a single root element. This element is either the representation of an entity, an entity reference or a complex type instance, a primitive value, a collection of primitive values, a collection of complex values, a collection of entities, or a collection of entries that represent changes to a previous result.

Relative URLs

OData payloads MAY use relative references as defined in [RFC3986] by specifying the xml:base attribute to define a base URI for relative references defined within the scope of the element containing the xml:base attribute.

5 Service Document

AtomPub defines the concept of a service document to represent the set of available collections. OData uses the service document to describe the entity sets, named entities, and parameterless function imports published by the service.

Example:

<app:service xmlns:app="http://www.w3.org/2007/app"

xmlns:atom="http://www.w3.org/2005/Atom"

xmlns:metadata="http://docs.oasis-open.org/odata/ns/metadata"

metadata:metadata="http://host:port/service/$metadata"

metadata:metadata-etag="Hugo"

<app:workspace>

<atom:title type="text">Data</atom:title>

<app:collection href="OrderDetails">

<atom:title type="text">Order Details</atom:title>

</app:collection>

<metadata:entity href="Contoso">

<atom:title>Contoso Ltd.</atom:title>

</metadata:entity>

<metadata:function-import href="TopProducts">

<atom:title>Best-Selling Products</atom:title>

</metadata:function-import>

<metadata:service-document href="EasternRegionSales">

<atom:title>Eastern Region Sales</atom:title>

</metadata:service-document>

</app:workspace>

</app:service>

5.1 Element app:service

The service document contains a single app:service element. The app:service element contains one or more app:workspace elements.

5.1.1 Element app:workspace

OData represents the each entity container as an app:workspace element. An app:workspace element contains zero or more app:collection elements, one for each entity set published by the container, zero or more metadata:function-import elements, one for each function import published by the continer, and zero or more metadata:entity elements, one for each named entity published by the container.

5.1.1.1 Attribute metadata:name

The metadata:name attribute MUST contain the namespace- or alias-qualified name of the entity container that is represented by the app:workspace element. It MAY be omitted if the workspace represents the default entity container.

For more information on namespace- and alias-qualified names, see [OData-CSDL].

5.1.1.2 Attribute metadata:metadata

An app:workspace element MUST have a metadata attribute, defined in the OData Metadata namespace, whose value is the URL that returns the metadata document of the service.

For more information on the format of the metadata document, see [OData-CSDL].

5.1.1.3 Attribute metadata:metadata-etag

An app:workspace element MAY have a metadata:metadata-etag attribute to specify an ETag that can be used to determine the current version of the service's metadata document.

For details on how ETags are used, see [Error! Reference source not found.].

5.1.1.4 Element title

As defined in [RFC-5023], the app:workspace element MUST contain a title element containing the human-readable description of the workspace. This value may be different from the name of the entity container exposed by the metadata:name attribute.

5.1.2 Element app:collection

OData represents entity sets that are not marked with IncludeInServiceDocument="false" (see [OData-CSDL]) as app:collection elements contained within the app:workspace element.

<app:collection href="OrderDetails">

<atom:title type="text">Order Details</atom:title>

</app:collection>

5.1.2.1 Attribute href

The app:collection element MUST contain an href attribute which represents a URL that can be used to retrieve the members of the entity set.

5.1.2.2 Attribute metadata:name

The metadata:name attribute MUST contain the name of the entity set which MAY be unqualified if the enclosing app:workspace represents the default entity container.

It MAY be omitted if its value is identical the the value of the href attribute, which is the case if the service uses relative URLs following the OData URL conventions described in Error! Reference source not found..

5.1.2.3 Element atom:title

The atom:title element within the app:collection MUST contain a human-readable description of the entity set which MAY be the name of the entity set.

5.1.3 Element metadata:function-import

OData represents function imports that are marked with IncludeInServiceDocument="true" (see [OData-CSDL]) as metadata:function-import elements.

5.1.3.1 Attribute href

The metadata:function-import element MUST contain an href attribute which represents a URL that can be used to retrieve the function import result.

5.1.3.2 Attribute metadata:name

The metadata:name attribute MUST contain the name of the function import which MAY be unqualified if the enclosing app:workspace represents the default entity container.

5.1.3.3 Element atom:title

The atom:title element within the metadata:function-import element MUST contain a human-readable description of the function import which MAY be the name of the function import.

5.1.4 Element metadata:entity

OData represents named entities as metadata:entity elements.

5.1.4.1 Attribute href

The metadata:entity element MUST contain an href attribute which represents a URL that can be used to retrieve the entity.

5.1.4.2 Attribute metadata:name

The metadata:name attribute MUST contain the name of the entity which MAY be unqualified if the enclosing app:workspace represents the default entity container.

5.1.4.3 Element atom:title

The atom:title element within the metadata:entity element MUST contain a human-readable description of the entity which MAY be the name of the entity.

5.1.5 Element metadata:service-document

OData represents related service documents as metadata:service-document elements.

<metadata:service-document href="EasternRegionSales">

<atom:title>Eastern Region Sales</atom:title>

</metadata:service-document>

5.1.5.1 Attribute href

The metadata:service-document element MUST contain an href attribute which represents a URL that can be used to retrieve the related service document.

5.1.5.2 Element atom:title

The metadata:service-document element MUST contain an atom:title element containing a human-readable description of the related service document.

6 Entity

Entities, whether individual or within an Atom feed, are represented as atom:entry elements.

Example:

<entry>

<id>http://services.odata.org/OData/OData.svc/Products(0)</id>

</author>

title="Category" href="Products(0)/Category" />

title="Supplier" href="Products(0)/Supplier" />

<metadata:properties>

<data:ID metadata:type="Int32">0</data:ID>

<data:Name>Bread</data:Name>

<data:Description>Whole grain bread</data:Description>

<data:ReleaseDate metadata:type="Date">

1992-01-01

</data:ReleaseDate>

<data:DiscontinuedDate metadata:type="Date" metadata:null="true" />

<data:Rating metadata:type="Int32">4</data:Rating>

<data:Price metadata:type="Decimal">2.5</data:Price>

</metadata:properties>

</content>

</entry>

This section defines the elements and attributes within an atom:entry element that are assigned meaning in OData.

6.1 Element atom:entry

An atom:entry element is used to represent a single entity, which is an instance of a structured type with an identity.

6.1.1 Attribute metadata:etag

The atom:entry element MAY contain a metadata:etag attribute, representing an opaque string value that can be used in a subsequent request to determine if the value of the entity has changed. For details on how ETags are used, see to [Error! Reference source not found.].

6.1.2 Attribute metadata:metadata

If the root of the response is an atom:entry element, or the entity set cannot be determined from the metadata URL of the feed, the atom:entry element MUST have a metadata attribute, defined in the OData Metadata namespace, whose value is the metadata URL that describes the entry. This URL MAY be absolute or relative to the metadata URL of the feed.

For more information on the metadata URL, see [Error! Reference source not found.].

6.1.3 Attribute metadata:metadata-etag

If the root of the response is an atom:entry element, it MAY have a metadata:metadata-etag attribute to specify an ETag that can be used to determine the current version of the service's metadata document.

For details on how ETags are used, see [Error! Reference source not found.].

6.2 Element atom:id

The atom:id element defines a durable, opaque, globally unique identifier for the entry. Its content must be an IRI as defined in RFC3987. The consumer of the feed must not assume this IRI can be de-referenced, nor assume any semantics from its structure.

6.2.1 Element atom:category

An OData entry MUST contain a single atom:category element with a scheme attribute equal to http://docs.oasis-open.org/odata/ns/scheme to identify the entity type of the entry.

An atom:category element describing an OData entity type MUST have a term attribute whose value is the namespace- or alias-qualified name of the entity type of the entry, in which case the type MUST be defined in the metadata document indicated by the current metadata URL, otherwise it MUST be a full URL to a metadata document with the namespace-qualified name of the instance’s type appended as a URL fragment.

For example, the following represents an entity whose type is “Model.VipCustomer”, defined within the current metadata document:

<category rel="http://docs.oasis-open.org/odata/ns/scheme"

term="Model1.VipCustomer"/>

The following represents an entity whose type is “Model.VipCustomer”, defined within the “http://host/alternate/$metadata” document:

<category rel="http://docs.oasis-open.org/odata/ns/scheme"

term="http://host/alternate/$metadata#Model1.VipCustomer"/>

For more information on namespace- and alias-qualified names, see [OData-CSDL].

The entry MAY contain additional atom:category elements with different scheme values; such atom:category elements have no semantic meaning in OData.

6.3 Element atom:content

The atom:content element contains the properties of the entity as a metadata:properties element unless the entity is a media entity.

6.3.1 Self and Edit Links

Atom defines two types of links within an entry that represent retrieve or update/delete operations on the entry:

· atom:link elements with a rel attribute of self can be used to retrieve the entity (via the URL specified in the href attribute).

· atom:link elements with a rel attribute of edit can be used to retrieve, update, or delete the entity (via the URL specified in the href attribute).

An atom:entry element representing an OData entity SHOULD contain a self link, an edit link, or both for a particular entry, but MUST NOT contain more than one edit link for a given entity. The absence of a self link implies that the edit link can be used to retrieve the entity. The absence of an edit link implies that the entity is read-only.

7 Property

7.1 Primitive Value

OData Atom and XML payloads represent values of primitive types following the rules of [GML] Portele, C., Ed., "OpenGIS Geography Markup Language (GML) Encoding", August 2007. http://portal.opengeospatial.org/files/?artifact_id=20509.

[OData-ABNF].

Geography and Geometry values are represented as defined in [GML].

Values of the other primitive types are represented according to the xxxValue rules, i.e. Edm.Binary as binaryValue etc.

Example:

<metadata:properties>

<data:NullValue metadata:null="true"/>

<data:TrueValue metadata:type="Boolean">true</data:TrueValue>

<data:FalseValue metadata:type="Boolean">false</data:FalseValue>

<data:IntegerValue metadata:type="SByte">-128</data:IntegerValue>

<data:DoubleValue metadata:type="Double"
>3.1415926535897931</data:DoubleValue>

<data:SingleValue metadata:type="Double">INF</data:SingleValue>

<data:DecimalValue metadata:type="Decimal">34.95</data:DecimalValue>

<data:StringValue>Say "Hello",
then go!</data:StringValue>

<data:DateValue metadata:type="Date">2012-12-03</data:DateValue>

<data:DateTimeOffsetValue metadata:type="DateTimeOffset"
>2012-12-03T07:16:23Z</data:DateTimeOffsetValue>

<data:DurationValue metadata:type="Duration"
>P12DT23H59M59.999999999999S</data:DurationValue>

<data:TimeOfDayValue metadata:type="TimeOfDay"
>07:59:59.999</data:TimeOfDayValue>

<data:GuidValue metadata:type="Guid"
>01234567-89ab-cdef-0123-456789abcdef</data:GuidValue>

<data:Int64Value metadata:type="Int64">0</data:Int64Value>

<data:ColorEnumValue metadata:type="org.example.Pattern"
>Yellow</data:ColorEnumValue>

<data:GeographyPoint metadata:type="GeographyPoint">

<gml:Point>

<gml:pos>64.1 142.1</gml:pos>

</gml:Point>

</data:GeographyPoint>

</metadata:properties>

Note that the line break in the body of StringValue is intentional, it represents a line break.

7.2 Element metadata:properties

The metadata:properties element represents property values for an entity.

7.3 Element data:[PropertyName]

Within the metadata:properties element, individual entity properties are represented as elements where the name of the element is the name of the entity property within the OData Data Namespace.

The data:[PropertyName] element MAY include a metadata:type attribute to specify the type of the primitive- or complex-typed instance.

For example, the following element within an metadata:properties element represents the “Rating” field with an integer value of 4:

<data:Rating metadata:type="Int32">4</data:Rating>

The data:[PropertyName] element MAY include a metadata:null attribute to specify that the primitive- or complex-typed instance has the null value.

For example:

<data:Rating metadata:null="true" />

7.3.1 Primitive and Enumeration Property

For primitive properties, the content of the data:[PropertyName] element represents the value of the property following the syntax for primitive values. For example, the following would represent the string value “CEO” for the Title property of an entity:

<data:Title>CEO</data:Title>

The following would represent the combined enumeration values Yellow and Solid for the Pattern property of an entity:

<data:Pattern metadata:type="org.example.Pattern">Solid,Yellow</data:Pattern>

7.3.2 Complex Property

For complex properties, the content of the data:[PropertyName] element consists of nested data:[PropertyName] elements describing the properties of the complex type. It MAY include a metadata:type attribute to specify the type.

For example, the complex typed property “Name”, with properties “FirstName” and “LastName” would be respresented as:

<data:Name metadata:type="MyModel.FullName">

<data:FirstName>Julie</data:FirstName>

<data:LastName>Swansworth</data:LastName>

</data:Name>

7.3.3 Primitive and Enumeration Collection Property

For properties that represent a collection of primitive or enumeration values, the data:[PropertyName] element may include a metadata:type attribute with a value of "Collection([PrimitiveTypeName])". The content of the element consists of nested child elements named “element” in the OData Metadata Namespace for each value in the collection.

The value of each <metadata:element> in the collection follows the syntax for primitive values.

<metadata:element> elements MUST NOT contain the metadata:null="true" attribute value.

Example:

<data:EmailAddresses metadata:type="Collection(String)">

<metadata:element>Julie@Swansworth.com</metadata:element>

<metadata:element>Julie.Swansworth@work.com</metadata:element>

</data:EmailAddresses>

7.3.4 Complex Collection Property

For properties that represent a collection of complex types, the data:[PropertyName] element may include a metadata:type attribute with a value of "Collection([ComplexTypeName])“ attribute. The content of the element consists of nested child elements named “element", in the OData Metadata Namespace, for each complex typed value in the collection.

The <metadata:element> element representing the instance may include a metadata:type attribute to specify the type of the individual element. The value of each complex-typed <metadata:element> follows the syntax for complex-typed properties.

metadata:element elements MUST NOT be empty and MUST NOT contain the metadata:null="true" attribute.

Example:

<data:PhoneNumbers metadata:type="Collection(Person.PhoneNumber)">

<metadata:element>

<data:Number>425-555-1212</data:Number>

<data:PhoneType>Home</data:PhoneType>

</metadata:element>

<metadata:element metadata:type="Person.CellPhoneNumber">

<data:Number>425-555-0178</data:Number>

<data:PhoneType>Cell</data:PhoneType>

<data:CellCarrier>Sprint</data:CellCarrier>

</metadata:element>

</data:PhoneNumbers>

7.3.5 Attribute metadata:null

Null-valued properties are represented as empty elements with the metadata:null="true" attribute.

The metadata:null attribute distinguishes null values from other empty content (such as an empty string).

For example, the following represents an empty apartment number:

<data:Apartment metadata:null="true"/>

The absence of the metadata:null attribute is equivalent to specifying metadata:null="false".

7.3.6 Attribute metadata:type

If the type of the property is anything other than Edm.String, the property representation MUST contain a metadata:type attribute to specify the namespace- or alias-qualified type of the property. If the type is defined in a different metadata document than specified by the current metadata URL, it MUST be a full URL to a metadata document with the namespace- or alias-qualified name of the instance’s type appended as a URL fragment.

For example, the following specifies that the Age property is a 32-bit integer with the value 25:

<data:Age metadata:type="Int32">25</data:Age>

8 Navigation Property

A navigation property represents a reference from a source entity to zero or more related entities.

Navigation Link

The navigation link is a URL that allows retrieving the related entity or collection of entities, It is represented as an atom:link element.

Example for products related to a category:

<atom:link

rel="http://docs.oasis-open.org/odata/ns/related/Products"

href="Categories(0)/Products"

type="application/atom+xml;type=feed"

title="Products"

The related data for the relationship MAY be included in the entity using a single child metadata:inline element.

8.1.1 Element atom:link

In the case where the atom:link element describes a navigation link the attributes rel, href, type, metadata:metadata, and title are to be used as described in the following subsections.

8.1.1.1 Attribute rel

The rel attribute MUST be present and is made up of the string “http://docs.oasis-open.org/odata/ns/related/” followed by the name of the navigation property on the entity.

Note that the full name must be used; the use of relative URLs in the rel attribute is not allowed.

8.1.1.2 Attribute href

The href attribute MUST be present and specifies the URL that can be used to retrieve the related entities. This URL may be relative or absolute.

8.1.1.3 Attribute type

The type attribute MUST be present and determines whether the cardinality of the related end is a single entity or a collection of entities. The value "application/atom+xml;type=entry" represents a single entity and the value "application/atom+xml;type=feed" an collection of entities.

8.1.1.4 Attribute metadata:metadata

The metadata:metadata Attribute MUST be present if the navigation property is not defined in metadata. The value of the metadata:metadata attribute, defined in the OData Metadata namespace, specifies the metadata URL that describes the type of the related entity or entities

For details on the metadata URL, see [Error! Reference source not found.].

8.1.1.5 Attribute title

The title attribute SHOULD be present and equal to the name of the navigation property, and provides human-readable, possibly language-dependent, and not necessarily unique information about the link.

8.2 Association Link

The association link is a URL that allows retrieving the reference or collection of references to the related entity or entities. It is represented as an atom:link element.

Example for products related to a category:

<atom:link

rel="http://docs.oasis-open.org/odata/ns/relatedlinks/Products"

href="Categories(0)/Products/$ref"

type="application/xml"

title="Products"

8.2.1 Element atom:link

A collection of relationship links is represented by an atom:link element. The attributes rel, href, type, metadata:metadata, and title are to be used as described in the following subsections.

8.2.1.1 Attribute rel

The rel attribute MUST be present. The value MUST be made up of the string "http://docs.oasis-open.org/odata/ns/relatedlinks/" followed by the name of the navigation property on the entity.

Note that the full name must be used; the use of relative URLs in the rel attribute is not allowed.

8.2.1.2 Attribute href

The href attribute MUST be present and MUST specify the URL that represents the collection of relationship links. This URL may be relative or absolute.

8.2.1.3 Attribute type

The type attribute MUST be present with the string "application/xml" as value.

8.2.1.4 Attribute title

The title attribute SHOULD be present and be set to the name of the navigation property. The title attribute provides human-readable, possibly language-dependent, and not necessarily unique information about the link.

8.3 Expanded Navigation Property

An expanded navigation property MUST be represented as a single metadata:inline child element of the atom:link element representing the navigation link. The value of the metadata:inline element MUST be the correct representation of the related entity or collection of entities.

It is valid to include the metadata:inline element in only a subset of the entries within a feed.

If at most one entity can be related, the value is the representation of the related entity, or the metadata:inline element is empty if no entity is currently related.

If a collection of entities can be related, it MUST be represented as an atom:feed. An empty set of entities (one that contains no entity type instances) MUST be represented as an empty atom:feed.

Each entity MUST be represented as an atom:entry element or as an entity reference.

Example:

<atom:link

rel="http://docs.oasis-open.org/odata/ns/related/Products"

href="Categories(0)/Products"

type="application/atom+xml;type=feed"

title="Products"

<metadata:inline>

<atom:feed>

...

</atom:feed>

</metadata:inline>

</atom:link>

8.4 Deep Inserts

When inserting a new entity with a POST request, related new entities MAY be specified using the same representation as for an expanded navigation property.

Deep inserts are not allowed in update operations using PUT or PATCH requests.

Example for inserting a new order with order details and a new customer:

<entry>

...

title="Customer" href=" Orders(11643)/Customer">

<metadata:inline>

<entry>

...

<metadata:properties>

<data:ID>ANEWONE</data:ID>

...

</metadata:properties>

</content>

</entry>

</metadata:inline>

</link>

title="Details" href="Orders(11643)/Details">

<metadata:inline>

<feed>

<entry>

...

<metadata:properties>

<data:ProductID metadata:type="Int32">28</data:ProductID>

...

</metadata:properties>

</content>

</entry>

<entry>

...

<metadata:properties>

<data:ProductID metadata:type="Int32">39</data:ProductID>

...

</metadata:properties>

</content>

</entry>

...

</feed>

</metadata:inline>

</link>

<metadata:properties>

<data:OrderID metadata:type="Int32">11643</data:ID>

<data:CustomerID>ANEWONE</data:CustomerID>

<data:EmployeeID metadata:type="Int32">6</data:EmployeeID>

...

</metadata:properties>

</content>

</entry>

8.5 Bind Operations

When inserting or updating an entity, relationships of navigation properties MAY be inserted or updated via bind operations.

If at most one entity can be related, the bind operation MUST be represented as a navigation link whose href attribute MUST contain the id of the entity to be related.

For update operations a bind operation on a collection navigation property MUST be represented as a navigation link with an inlined collection of entity references. The referenced entities are added as additional related entities, and existing relationships are not updated or deleted.

For insert operations collection navigation property bind operations and deep insert operations MAY be combined by inlining an atom:feed that contains atom:entry elements and metadata:ref elements.

Example for assigning a product to an existing category with an update request:

<atom:link

rel="http://docs.oasis-open.org/odata/ns/related/Category"

href="http://host/service/Categories(0)"

type="application/atom+xml;type=entry"

title="Category"

9 Stream Property

9.1 Element atom:link

An entity may have one or more stream properties (for example, a photo property of an employee entity). Properties that represent streams have a type of Edm.Stream.

OData uses the atom:link element to represent a named stream property of an entity.

For example, a stream property named “Photo” could be represented by an atom:link element as a child of the atom:entry element as follows:

<atom:link rel="http://docs.oasis-open.org/odata/ns/mediaresource/Photo"

type="image/jpeg" title="Photo" href="Categories(0)/Photo"

A stream property named “Photo” could be edited through an atom:link element as a child of the atom:entry element as follows:

<atom:link
rel="http://docs.oasis-open.org/odata/ns/edit-media/Photo"

type="image/jpeg" title="Photo" href="Categories(0)/Photo"

The attributes rel, href, type, metadata:etag, and title are to be used as described in the following subsections.

9.1.1 Attribute rel

The rel attribute MUST be present and MUST be made up of the string http://docs.oasis-open.org/odata/ns/mediaresource/, followed by the name of the stream property on the entity.

The rel attribute for an atom:link element that can be used to change a stream property value is made up of the string http://docs.oasis-open.org/odata/ns/edit-media/, followed by the name of the stream property on the entity.

In both cases the full name must be used; the use of relative URLs in the rel attribute is not allowed.

9.1.2 Attribute href

The href attribute MUST be present and MUST contain the URL that can be used to read, or write, the stream, according to the rel attribute. This URL may be relative or absolute.

9.1.3 Attribute type

The type attribute specifies the meda-type of the stream property.

9.1.4 Attribute metadata:etag

The metadata:etag attribute specifies an etag value that can be used in an if-match header to conditionally write to the stream property as described in [Error! Reference source not found.].

9.1.5 Attribute title

The title attribute provides human-readable, possibly language-dependent, and not necessarily unique information about the link. It has no implied semantics in OData.

10 Media Entity

Media entities (in AtomPub: media link entries, see [RFC5023]) are entities that describe and link to a media resource.

<entry>

<id>http://host/service/Employees(6)</id>

...

<metadata:properties>

<data:ID metadata:type="Int32">6</data:ID>

...

</metadata:properties>

</entry>

10.1 Element atom:link

A media entity MAY contain an atom:link element with a rel attribute of "edit-media" to specify a URL that can be used to write to the BLOB associated with the entity. The attributes rel and href MUST be used as described in the following subsections.

10.1.1 Attribute rel

The rel attribute MUST be present and MUST have the string “edit-media” as value.

10.1.2 Attribute href

The href MUST be present and its value MUST specify the URI that can be used to write the stream. This URI may be relative or absolute.

10.2 Element atom:content

For media entities the atom:content element MUST be empty. Properties of the media entity are represented by the metadata:properties element as a sibling to, rather than a child of, the atom:content element.

10.2.1 Attribute src

The atom:content element MUST contain a src attribute and the value of the src attribute MUST be a URL that can be used to retrieve the content of the media resource.

10.2.2 Attribute type

The atom:content element MUST specify a type attribute that SHOULD contain the MIME type of the media resource.

11 Individual Property

A valid OData payload may consist of a single primitive or complex value, or of a collection of these.

11.1 Single Scalar Value

For example, a request for the first name of a given customer may return the following payloads:

<metadata:value xmlns:metadata=="http://docs.oasis-open.org/odata/ns/metadata"

metadata:null="true" />

Similarly, the following payload represents a full name:

<metadata:value metadata:type="HumanResources.Address"

xmlns:metadata="http://docs.oasis-open.org/odata/ns/metadata"

xmlns="http://docs.oasis-open.org/odata/ns/data">

<FirstName>Julie</FirstName>

<LastName>Swansworth</LastName>

</metadata:value>

11.1.1 Element metadata:value

Single scalar values are represented as a metadata:value root element that contains the representation of the scalar value. The attributes metadata:type and metadata:null MUST be used as described in the following subsections.

11.1.1.1 Attribute metadata:metadata

The metadata:value element MUST have a metadata attribute, defined in the OData Metadata namespace, whose value is the metadata URL that describes the element.

For more information on the metadata URL, see [Error! Reference source not found.].

11.1.1.2 Attribute metadata:metadata-etag

The metadata:value element MAY have a metadata:metadata-etag attribute to specify an ETag that can be used to determine the current version of the service's metadata document.

For details on how ETags are used, see [Error! Reference source not found.].

11.1.1.3 Attribute metadata:type

If the type of the scalar value being specified is anything other than Edm.String the metadata:type attribute MUST be present and specify the namespace - or alias - qualified type of the value.

11.1.1.4 Attribute metadata:null

The metadata:null attribute distinguishes null values from other empty content (such as an empty string).

Null-values are represented as an empty metadata:value element with a metadata:null="true" attribute.

11.2 Collection of Scalar Values

A valid OData payload MAY consist of a collection of primitive or complex properties.

For example, the following payload represents a collection of phone numbers.

<metadata:value xmlns:metadata="http://docs.oasis-open.org/odata/ns/metadata">

<metadata:element>(203)555-1718</metadata:element>

<metadata:element>(203)555-1719</metadata:element>

</metadata:value>

Similarly, the following payload represents a collection of full names.

<metadata:value xmlns:metadata="http://docs.oasis-open.org/odata/ns/metadata"

xmlns="http://docs.oasis-open.org/odata/ns/data">

<metadata:element metadata:type="HumanResources.FullName">

<FirstName>Julie</FirstName>

<LastName>Swansworth</LastName>

</metadata:element>

<metadata:element metadata:type="HumanResources.FullName">

<LastName>Swansworth</LastName>

</metadata:element>

</metadata:value>

11.2.1 Element metadata:value

A Collection of scalar values is represented as a single metadata:value root element that contains a <metadata:element> child element for each member of the collection whose content is an individual primitive or complex value as defined above.

The <metadata:value> element MUST NOT contain a metadata:null attribute. The attribute metadata:type MUST be used as described in the following subsection.

11.2.1.1 Attribute metadata:type

The attribute metadata:type MUST be present and specify the namespace- or alias-qualified collection type.

For collections of complex scalar values this attribute specifies a collection type for the base type of the collection. Individual elements of a derived type MUST specify their derived types with a metadata:type attribute on the <metadata:element> element.

12 Collection of Entities

Collections of entities are represented in Atom as an Atom Feed.

12.1 Element atom:feed

Collections of entities are represented using an atom:feed Element, where each entity is represented as an atom:entry or metadata:ref.

12.1.1 Attribute metadata:metadata

The atom:feed element, it MUST have a metadata attribute, defined in the OData Metadata namespace, whose value is the metadata URL that describes the feed.

For more information on the metadata URL, see [Error! Reference source not found.].

12.1.2 Attribute metadata:metadata-etag

The metadata:metadata-etag attribute MAY appear in an atom:feed in order to specify an ETag that can be used to determine the current version of the service's metadata document.

For details on how ETags are used, see [Error! Reference source not found.].

12.1.3 Element atom:id

OData does not add any conventions or semantics beyond [RFC4287] to the atom:id element for feeds.

12.1.4 Element metadata:count

The atom:feed element MAY contain a metadata:count element to specify the total count of rows in the result. This MAY be greater than the number of rows in the feed if server side paging has been applied, in which case the feed MUST include a next results link:

<feed xmlns="http://www.w3.org/2005/Atom"

xmlns:metadata="http://docs.oasis-open.org/odata/ns/metadata" >

<metadata:count>42</metadata:count>

...

</feed>

12.1.5 Element atom:link

Atom requires that feeds contain a “self link”. The atom:feed element MAY contain a next link to indicate the presence of additional entries that belong to the feed. The atom:feed element representing the final page of results may contain a delta link that can be used to fetch subsequent changes (deltas) to the result.

All three cases are distinguished from another by the value of the rel attribute as described in the following subsection.

Note that the actual set of entries contained within the atom:feed MAY be a subset of those retrieved using the self link, for example, if filtering has been applied.

12.1.5.1 Attribute rel

A self link is represented as an atom:link with a rel="self" attribute and an href that can be used to retrieve the feed from which the current entries are taken. If the feed represents a set of related entities (addressed with a request URL ending in a to-many navigation property, or an inlined feed requested with $expand), the self link MUST identify the specific feed of related entities.

A next link is represented as an atom:link with a rel="next" attribute and an href attribute containing a URL that can be used to retrieve the next set of results.

For example, the following atom:link element within an atom:feed element indicates that additional results can be returned by following the specified href:

<atom:link rel="next"

href="http://myservice/customers?$skiptoken=1237"/>

The contents of the href SHOULD be treated as an opaque URL that can be used to fetch the next set of results.

A delta link is represented as an atom:link element with a rel attribute of " http://docs.oasis-open.org/odata/ns/delta" and an href attribute containing a URL that can be used to retrieve subsequent changes.

For example, the following atom:link element within an atom:feed element indicates that changes may be retrieved by following the specified href:

<atom:link rel=" http://docs.oasis-open.org/odata/ns/delta"

href="http://myservice/customers?$deltatoken=1234"/>

The contents of the href should be treated as an opaque URL that can be used to fetch subsequent changes.

The delta link MUST only appear on the last page of results. A page of results MUST NOT have both a delta link and a next link.

13 Resource Reference

A resource reference is a reference to an entity or a property of an entity. A resource reference referring to an entity is called an entity reference.

An entity reference MAY take the place of an entity instance in an Atom payload, based on the client request.

For example, the following shows an entity reference to order 10643:

<metadata:ref ref="http://services.odata.org/OData/OData.svc/Orders(10643)" />

13.1 Element metadata:ref

A reference to an entity or one of its properties is represented in Atom using a metadata:ref element. The ref attribute MUST be present and used as described in the following subsection.

13.1.1 Attribute ref

The ref attribute MUST be present. For entities the ref attribute MUST be the atom:id of the referenced entity, for entity properties it MUST be the atom:id of the entity followed by the resource path segment identifying the property.

14 Delta Response

Responses from a delta request are returned as an atom:feed. The feed MUST contain all added, changed, or deleted entities, as well as added or deleted links between entities, and MAY contain additional, unchanged entities.

All added, changed, or deleted entities and links, including related entities, are returned as direct children of the atom:feed element.

Entities that are not part of the set specified by the value of metadata:metadata MUST include the metadata:metadata attribute in the atom:id element to specify the set of the related entity.

If the delta response contains a partial list of changes, it MUST include a next link for the client to retrieve the next set of changes.

Changes are generally ordered by the service according to when the last change occurred to an entity, but MUST be ordered such that applying all changes across all pages, in order, to the initial set yields a consistent result.

The last page of a delta response SHOULD contain a delta link for retrieving subsequent changes once the current set of changes has been applied to the initial set.

If the response from the delta link contains an inlinecount, the returned count is the count of added, changed, or deleted entities. $count and $inlinecount returned from a delta link do not include added or deleted links.

The following example shows the following ordered changes:

1. ContactName for customer 'BOTTM' was changed to "Susan Halvenstern"

2. Order 10643 was removed from customer 'ALFKI'

3. Order 10645 was added to customer 'BOTTM'

4. The shipping information for order 10643 was updated

5. Customer 'ANTON' was deleted

<?xml version="1.0" encoding="utf-8" standalone="yes" ?>

<feed xml:base="http://northwinddelta.cloudapp.net/DeltaService.svc/"

xmlns:data="http://docs.oasis-open.org/odata/ns/data"

xmlns:metadata="http://docs.oasis-open.org/odata/ns/metadata"

xmlns="http://www.w3.org/2005/Atom"

xmlns:at="http://purl.org/atompub/tombstones/1.0" >

<title type="text">Customers</title>

<id>http://DeltaService.svc/Customers</id>

<entry>

<id>http://DeltaService/Customers('BOTTM')</id>

<metadata:properties>

<d:ContactName>Susan Halvenstern</d:ContactName>

</metadata:properties>

</content>

</entry>

<metadata:deleted-link-entry

source="http://DeltaService/Customers('ALFKI')"

relationship="Orders"

target="http://DeltaService/Orders(10643)"

when="2011-02-16T01:00:25Z"/>

<metadata:link-entry

source="http://DeltaService/Customers('BOTTM')"

relationship="Orders"

target="http://DeltaService/Orders(10645)"

when="2011-02-16T01:00:25Z"/>

<id>http://DeltaService/Orders('10643')</id>

<metadata:properties>

<d:ShipName>Bottom-Dollar Markets</d:ShipName>

<d:ShipAddress>23 Tsawassen Blvd.</d:ShipAddress>

<d:ShipCity>Tsawassen</d:ShipCity>

<d:ShipRegion>BC</d:ShipRegion>

<d:ShipPostalCode>T2F 8M4</d:ShipPostalCode>

<d:ShipCountry>Canada</d:ShipCountry>

</metadata:properties>

</content>

</entry>

<at:deleted-entry

ref="http://DeltaService/Customers('ANTON')"

when="2011-02-16T01:00:30Z"

metadata:reason="deleted"/>

<link

rel="http://odata.org/deltaLink"

href="http://DeltaService/Customers?$expand=orders&$deltatoken=8015"/>

</feed>

14.1 Added/Changed Entity

Added or changed entities within a delta response are represented as atom:entry elements.

Added or changed entities MUST NOT include inline content.

Added entities MUST include all selected properties and MAY include additional, unselected properties. Collection-valued properties are treated as atomic values; any collection-valued properties returned from a delta request MUST contain all current values for that collection.

Added entities MUST include navigation links.

Changed entities MUST include all selected properties that have changed and MAY include additional properties.

Entities whose set cannot be determined from the metadata URL of the feed MUST include the metadata:metadata attribute in the atom:entry element to specify the metadata URL of the entity (in this metadata URL specifies the set, the entity belongs to). This metadata URL MAY be absolute or relative to the metadata URL of the feed.

14.2 Deleted Entity

14.2.1 Element atom-tombstone:deleted-entry

A deleted entitiy within a delta response is represented as an atom-tombstone:deleted-entry element, defined within the Atom Tombstone namespace, as defined in [RFC6721].

The ref and a when attribute MUST be present, the metadata:reason attribute MAY be present. All attributes have to be used as described in the following subsection.

14.2.1.1 Attribute ref

As defined in [RFC6721], the ref attribute MUST be present. The value of the ref attribute MUST specify the atom:id of the deleted entry.

14.2.1.2 Attribute when

As defined in [RFC6721], the when attribute MUST be present The value of the when attribute MUST specify the time at which the entity was deleted. The value may be the empty string if the service is unable to determine the time at which the deletion occurred.

14.2.1.3 Attribute metadata:reason

The metadata:reason attribute MAY be present. The value of the metadata:reason attribute MUST specify the string value "deleted", if the entity was deleted (destroyed), or "changed" if the entity was removed from membership in the result (i.e., due to a data change).

14.3 Link

14.3.1 Element metadata:link-entry

A Link within a delta response is represented by a metadata:link-entry element.

A Delta Response MUST contain a metadata:link-entry for each added link that corresponds to a $expand path in the initial request.

The source, relationship, and target attribute MUST be present, the when attribute MAY be present. All attributes have to be used as described in the following subsection.

14.3.1.1 Attribute source

The source attribute MUST be present and specify the atom:id of the entity from which the link originates.

14.3.1.2 Attribute relationship

The relationship MUST be present and specify the name of the navigation property on the source entity for which the link exists.

14.3.1.3 Attribute target

The target attribute MUST be present and specify the atom:id of the related entity.

14.3.1.4 Attribute when

The when attribute MAY be present and specify the time at which the link was created. The attribute MAY be the empty string if the service is unable to determine the time at which the creation occurred.

14.4 Deleted Link

14.4.1 Element metadata:deleted-link-entry

A Deleted Link within a delta response is represented as a metadata:deleted-link-entry element.

Delta responses MUST contain a metadata:deleted-link-entry for each deleted link that corresponds to a $expand path in the initial request, unless either of the following is true:

· The source or target entity has been deleted

· The maximum cardinality of the related entity is one and there is a subsequent metadata:link-entry that specifies the same source and relationship.

The service MAY return a metadata:deleted-link-entry where one of the entitites has also been deleted, or where there is a subsequent metadata:link-entry with the same source and relationship and a maximum cardinality of one for the related end.

The source, relationship and target attribute MUST be present, the when attribute MAY be present. All attributes have to be used as described in the following subsection.

14.4.1.1 Attribute source

The source attribute MUST be present and specify the atom:id of the entity from which the link originates.

14.4.1.2 Attribute relationship

The target attribute MUST be present and specify the atom:id of the related entity.

14.4.1.3 Attribute target

The target attribute MUST be present and specify the atom:id of the related entity.

14.4.1.4 Attribute when

15 Function

Zero or more functions MAY be bindable to a feed or entry.

The functions associated with a particular feed or entry MAY be described using metadata:function elements that are direct children of the feed or entry to which the functions can be bound.

Example:

<metadata:function

metadata="#DemoService.TopProducts"

target="http://host/service/Categories(0)/TopProducts"

title="Best-Selling Products"

15.1 Element metadata:function

Each function is represented as a metadata:function element that MUST be a child of the atom:feed or atom:entry element representing the collection or entity on which the function exists.

15.1.1 Attribute metadata

The metadata attribute MUST be present and specify the namespace- or alias-qualified name of the function, preceded by a #.

A function may have multiple overloads with different parameters. If the URL in the target attribute of the metadata:function element cannot be used to invoke all overloads for the function, then it MUST further be distinguished by appending a comma-separated ordered list of parameter type names, enclosed in parenthesis. For example, #Schema.Function(Schema.Product,Edm.String).

Example:

<metadata:function

metadata="#DemoService.TopProducts(DemoModel.Category,Edm.String)"

target="http://host/service/Categories(0)/TopProducts"

title="Best-selling products"

Attribute target

The target attribute MUST be present and specify the URL to GET from in order to invoke the function.

The first parameter of the function MUST be a binding parameter that is bound to the feed or entity on which the function is specified, and MUST NOT be provided as a separate parameter by the client when invoking the function.

15.1.2 Attribute title

The title attribute MUST be present and contain a human-readable, possibly language-dependent, and not necessarily unique name for the function, commonly used by clients to describe the function to a user.

16 Action

Zero or more actions may be bindable to a feed or entry.

The actions associated with a particular feed or entry MAY be described using metadata:action elements that are direct children of the feed or entry to which the actions can be bound.

Example:

<metadata:action

metadata="#DemoService.OrderProduct"

target="http://services.odata.org/OData/OData.svc/Products(1)/OrderProduct"

title="Order"

16.1 Element metadata:action

Each action is represented as a metadata:action element that MUST be a direct child of the atom:feed or atom:entry element representing the feed or entity on which the action exists.

16.1.1 Attribute metadata

The metadata attribute MUST be present and specify the namespace- or alias-qualified name of the action element describing the action, preceded by a #.

This function element name combined with the binding parameter type MUST be unique within the entity container.

16.1.2 Attribute target

The target attribute MUST be present and specify the URL to POST to in order to invoke the action.

The first parameter of the action MUST be a binding parameter that is bound to the feed or entity on which the action is specified, and MUST NOT be provided as a separate parameter by the client when invoking the action.

16.1.3 Attribute title

The title attribute MUST be present and contain a human-readable, possibly language-dependent, and not necessarily unique name for the action, commonly used by clients to describe the action to a user.

17 Action Parameters

Action parameter values in the request body MUST be encoded as an individual complex scalar value with the name parameters and no metadata:type attribute for the parameters element.

Each non-binding parameter value specified MUST be encoded as an individual primitive or complex scalar value. The name of the scalar value is the name of the parameter. The value is the parameter value in the XML representation appropriate for its type.

Any parameter values not specified in the request body MUST be assumed to have the default value specified in the service metadata, see [OData-CSDL].

Example:

<Street>One Microsoft Way</Street>

</param2>

</param3>

18 Instance Annotations

Annotations MAY be applied to an instance of a feed, entity, property, complex scalar value, function, action, or error within an Atom payload.

18.1 Element metadata:annotation

An instance annotation in Atom is represented as an XML element with the name Annotation in the metadata namespace.

The value of the annotation is specified according to the Annotation Value, described below.

18.1.1 Attribute target

The target attribute MAY be used to specify the annotation target. If the target attribute is not specified the target of the annotation is the element represented by the direct parent of the metadata:annotation element.

18.1.2 Attribute term

The metadata:annotation element MUST have a term attribute that specifies the namespace- or alias-qualified name of the term being applied.

18.1.3 Attribute metadata:type

If the type of the annotation value being specified is anything other than Edm.String the metadata:annotation element MUST contain a metadata:type attribute to specify the appropriate type of the annotation value.

18.1.4 Attribute metadata:null

Null-valued annotations are represented as empty metadata:annotation elements with the metadata:null="true" attribute.

The metadata:null attribute distinguishes null values from other empty content (such as an empty string).

The absence of the metadata:null attribute is equivalent to specifying metadata:null="false".

18.2 Annotation Values

An instance annotation value may be specified as a primitive value, structured value, or collection value.

18.2.1 Primitive Values

When specified in the content of an annotation element representing a primitive value, the content MUST be formatted as per Primitive Types in Atom. If the type of the annotation value is anything other than Edm.String, then the annotation element MUST contain the metadata:type attribute specifying the appropriate primitive type.

For example; the following annotates the "Phone" property with a string value of "Home" for the “PhoneNumberType” annotation term.

<metadata:properties>

<data:CustomerID>ALFKI</data:CustomerID>

<data:ContactName> Alfreds Futterkiste </data:ContactName>

<data:Phone>030-0074321</data:Phone>

<metadata:annotation term="com.contoso.PersonalInfo.PhoneNumberType"

target="Phone">Home</metadata:annotation>

</metadata:properties>

18.2.2 Collection Values

The content of an element representing a collection-valued annotation MUST be the individual elements of that collection formatted as direct child elements of the metadata:annotation element as described in Collections of Primitive or Complex Scalar Values.

For collection-valued annotations, the annotation element MUST contain the metadata:type attribute specifying the appropriate collection type.

For example, the following annotates the customer instance with two phone numbers.

<entry>

<id>Customers(ALFKI)</id>

<metadata:properties>

<data:CustomerID>ALFKI</data:CustomerID>

<data:ContactName>Alfreds Futterkiste</data:ContactName>

<data:Phone>030-0074321</data:Phone>

</metadata:properties>

</content>

<metadata:annotation term="com.contoso.PersonalInfo.PhoneNumbers"

type="Collection(String)">

</metadata:annotation>

</entry>

18.2.3 Structure Annotations

The content of an element representing a structured annotation MUST be a single child element for each property of the annotation type being specified, formatted as per properties within an entity type.

For structural-valued annotations, the annotation element MUST contain the metadata:type attribute specifying the appropriate structural type.

For example; the following specifies the StreetAddress, City, Region, Country and PostalCode properties of an Address annotation applied to a customer entity:

<entry>

<id>Customers(ALFKI)</id>

<metadata:properties>

<data:CustomerID>ALFKI</data:CustomerID>

<data:ContactName>Alfreds Futterkiste</data:ContactName>

<data:Phone>030-0074321</data:Phone>

</metadata:properties>

</content>

<metadata:annotation term="com.contoso.Locations.Address"
type="Locations.Address">

<data:StreetAddress>Obere Str. 578</data:StreetAddress>

<data:City>Toronto</data:City>

<data:Region metadata:null="true"/>

<data:PostalCode>12209</data:PostalCode>

<data:Country>Germany</data:Country>

</metadata:annotation>

<entry>

18.3 Instance Annotation Targets

Instance annotations may target model elements represented by a feed, entity, complex scalar value, property, function, action, or error element in an Atom payload.

18.3.1 Feed

When annotating a feed, annotation elements MUST be direct children of the atom:feed element, and they MUST appear in a group at the beginning of the feed or (another) group at the end of the feed, depending on whether they are needed beforehand to understand the feed content, or can only be computed after serializing the feed content.

18.3.2 Entry

When annotating an entity, the annotation element MUST be a direct child of the atom:entry element representing the entity.

18.3.3 Complex Type

When annotating an instance of a complex type, the annotation element MUST be a direct child of the metadata:value element representing the complex-typed value.

18.3.4 Property

When annotating a property, the annotation element MUST be a direct child of the metadata:properties element, or a direct child of the element representing a complex type in the case of annotating the property of a complex type. The value of the target attribute MUST specify the name of the property being annotated. The annotation elements MUST immediately precede the target property element.

Instance annotations are not supported when serializing single primitive properties in XML as described in Individual Primitive or Complex Scalar Values .

18.3.5 Navigation Property

When annotating a navigation property, named stream, or other element represented by an atom:link element, the annotation element must be a direct child of the atom:link element.

18.3.6 Function or Action

When annotating a function or action, the annotation element must be a direct child of the element representing the function or action.

18.3.7 Error

When annotating an error, the metadata:annotation element MUST be a direct child of the metadata:error element. The annotation element MAY have a target attribute value of "code", "message", or "innererror". If the target attribute is not specified, then the annotation is applied to the error itself. The annotation elements MUST follow the other child elements of the error element.

19 Error Reponse

In the case of an error being generated in response to a request specifying an Accept header of application/xml or application/atom+xml, or that does not specify an Accept header, the service MUST respond with an error formatted as XML.

When formatting error responses as XML, servers SHOULD include a Content-Type response header with the value "application/xml".

19.1 Element metadata:error

Errors formatted as XML MUST have a root metadata:error element. The metadata:error element MUST have at least two child elements: metadata:code and metadata:message.

In addition, errors may be annotated using custom annotations.

For example:

<message>Functionality not supported.</message>

<message>$search query option not supported.</message>

<target>$search</target>

</detail>

</details>

</error>

19.2 Element metadata:code

The metadata:error element MUST contain one metadata:code element specifying a service-defined string. This value MAY be used to provide a more specific substatus to the returned HTTP response code.

19.3 Element metadata:message

The metadata:error element MUST contain a metadata:message element specifying a human readable, language-dependent message describing the error. The Content-Language header MUST contain the language code from [RFC5646] corresponding to the language in which the value for message is written.

19.4 Element metadata:target

The metadata:error element MAY contain a metadata:target element to specify the target of the error (for example, the name of the property in error).

19.5 Element metadata:details

The metadata:error element MAY contain a metadata:details element containing one or more metadata:detail elements specifying detail about the error.

19.5.1 Element metadata:detail

The metadata:detail element specifies information about an individual error detail.

19.5.2 Element metadata:code

The metadata:detail element MUST contain one metadata:code element specifying a service-defined string. This value MAY be used to provide a more specific substatus to the returned HTTP response code.

19.5.3 Element metadata:message

The metadata:detail element MUST contain a metadata:message element specifying a human readable, language-dependent message describing the error.

19.5.4 Element metadata:target

The metadata:detail element MAY contain a metadata:detail element to specify the target of the error.

19.6 Element metadata:innererror

The metadata:error element MAY contain a metadata:innererror element containing service specific debugging information that might assist a service implementer in determining the cause of an error.

The metadata:innererror element SHOULD only be used in development environments in order to guard against potential security concerns around information disclosure.

20 Extensibility

Implementations MAY add custom content anywhere allowed by [RFC4287], Section 6, “Extending Atom”, and [RFC5023], Section 6.2 “Document Extensibility”. However, custom elements and attributes MUST NOT be defined in the OData Data Namespace nor the OData Metadata Namespace, and SHOULD not be required to be understood by the receiving party in order to correctly interpret the rest of the payload as the receiving party MUST ignore unknown foreign markup according to [RFC4287].

21 Conformance

Conforming clients MUST be prepared to consume a service that uses any or all of the constructs defined in this specification. The exception to this are the constructs defined in Delta Response, which are only required for clients that request changes

The exception to this are the constructs defined in Delta Response, which are only required for clients that request changes.

A conforming OData service MUST comply with one of the conformance levels defined in [Error! Reference source not found.].

In order to conform to the OData Atom format, a service:

· MUST support the application/atom+xml, application/xml and application/atomsvc+xml media types in the Accept header

· SHOULD support the $format system query option

· MUST include the next link in feeds containing partial results

· MUST return service documents as Atom service documents

· MUST return XML responses in well formed XML according to this specification

· MUST return well-formed Atom payloads with the following exceptions:

o The next link MAY be returned at the end of the payload

o The delta link MAY be returned at the end of the payload

· MUST NOT violate any other aspects of this OData Atom specification

In order to be a conforming consumer of the OData ATOM format, a client or service:

· MUST be prepared to receive all data types

o defined in this specification defined in [OData-CSDL] (client)

o exposed by the service (service)

· MUST be prepared to receive custom annotations

· MUST be prepared to receive additional constructs not defined in this version of the specification

Appendix A. Acknowledgments

The contributions of the OASIS OData Technical Committee members, enumerated in [OData-Protocol][OData-Protocol], are gratefully acknowledged.

Appendix B. Revision History

Revision	Date	Editor	Changes Made
Working Draft 01	2012-08-22	Michael Pizzo	Translated Contribution to OASIS format/template