Skip navigation.
Downloads | Product Documentation | Support

XQuery Developer's Guide

# Understanding Data Services Platform Annotations

This chapter describes the syntax and semantics of BEA AquaLogic Data Services Platform (DSP) annotations in data service and XQuery function library (XFL) documents. Data service and XQuery function library documents define collections of XQuery functions. Annotations are XML fragments comprising the character content of XQuery pragmas.

There are two types of annotations:

- Global annotations. These pertain to the entire data service or XFL document. Global annotations are also referred to as XDS or XFL annotations respectively.
- Local annotations. These pertain to a particular function. Local annotations are also referred to as function annotations.

This chapter includes the following topics:

- XDS Annotations
- XFL Annotations
- Function Annotations

See XML Schema for Annotations, for a listing of the XML Schema for annotations.

# XDS Annotations

There is a single XDS annotation per data service document, which appears before all function annotations. The identifier for the pragma carrying the XDS annotation is xds. The qualified name of the top level element of the XML fragment corresponding to an XDS annotation has the local name `xds` and the namespace URI `urn:annotations.ld.bea.com`.

Each data service is associated with a unique target type. The prime type of the return type of every read function must match its target type. The target type of a data service is an element type whose qualified name is specified by the `targetType` attribute of the xds element. It is defined in a schema file associated with that data service.

The contents of the top-level `xds` element is a sequence of the following blocks of properties:

- General Properties
- Data Access Properties
- Target Type Properties
- Key Properties
- Relationship Properties
- Update Properties
- Security Properties

The following excerpt provides an example of an XDS annotation. In this case, the target type `t:CUSTOMER` associates the data service with a `t:CUSTOMER` type in a schema file.

>     (::pragma xds <x:xds xmlns:x="urn:annotations.ld.bea.com" targetType="t:CUSTOMER" xmlns:t="ld:oracleDS/CUSTOMER">

>     <author>Joe Public</author>
>     <relationalDB name="OracleDS"/>

>     <field type="xs:string" xpath="FIRST_NAME">
>     	<extension nativeFractionalDigits="0" nativeSize="64"
>     		nativeTypeCode="12" nativeType="VARCHAR2"
>     		nativeXpath="FIRST_NAME"/>
>     		<properties nullable="false"/>
>     </field>

>     <field type="xs:string" xpath="LAST_NAME">
>     	<extension nativeFractionalDigits="0" nativeSize="64"
>     		nativeTypeCode="12" nativeType="VARCHAR2"
>     		nativeXpath="LAST_NAME"/>
>     	<properties nullable="false"/>
>     </field>

>     <field type="xs:string" xpath="CUSTOMER_ID">
>     	<extension nativeFractionalDigits="0" nativeSize="64"
>     		nativeTypeCode="12" nativeType="VARCHAR2"
>     		nativeXpath="CUSTOMER_ID"/>
>     	<properties nullable="false"/>
>     </field>

>     <field type="xs:dateTime" xpath="CUSTOMER_SINCE">
>     	<extension nativeFractionalDigits="0" nativeSize="7"
>     		nativeTypeCode="93" nativeType="DATE"
>     		nativeXpath="CUSTOMER_SINCE"/>
>     	<properties nullable="false"/>
>     </field>

>     <field type="xs:string" xpath="EMAIL_ADDRESS">
>     	<extension nativeFractionalDigits="0" nativeSize="32"
>     		nativeTypeCode="12" nativeType="VARCHAR2"
>     		nativeXpath="EMAIL_ADDRESS"/>
>     	<properties nullable="false"/>
>     </field>

>     <key name="CUSTOMER_PK11015727676593">
>     	<field xpath="CUSTOMER_ID">
>     		<extension nativeXpath="CUSTOMER_ID"/>
>     	</field>
>     </key>

>     <relationshipTarget roleName="CUSTOMER_ORDER" roleNumber="2"
>     	XDS="ld:oracleDS/CUSTOMER_ORDER.xds" minOccurs="0"
>     	maxOccurs="unbounded" opposite="CUSTOMER"/>
>     </x:xds>::)

## General Properties

There are two types of general XDS properties:

- Standard Document Properties
- User-Defined Properties

### Standard Document Properties

You can specify a set of standard document properties consisting of optional XML elements containing information pertaining to the author, creation date, or version of the document. You can also use the optional element documentation to specify related documentation. The names and types of the elements in the standard document properties block, as well as examples of their use, are shown in Table 5-1.

Table 5-1 Standard Document Properties

Element Name | Element Type | Optional | Example Instance
--- | --- | --- | ---
author | xs:string | Yes | <author>J. Public</author>
creationDate | xs:date | Yes | <creationDate>2004-05-31</creationDate>
version | xs:decimal | Yes | <version>2.2<version>
documentation | xs:string | Yes | <documentation> Models an online Customer </documentation>

### User-Defined Properties

In addition to the standard properties, you can specify custom properties pertaining to the entire data service document using a sequence of zero (0) or more `property` elements. Each property element must be named using its name attribute and may contain any string content. For example:

>     <property name="data-refresh-rate">week</property>

## Data Access Properties

Each data service document defines one or more XQuery functions that act as either data providers or data transducers. A data provider, or data source, is a function that is declared as external; its invocation causes data from an external source to be brought into the system. A data transducer, or data view, is defined in XQuery and it typically performs transformations on data derived from data sources or other data views.

The block of data access properties allows each data service to define whether its read functions include data sources or not. When data sources are included, the data access annotation describes the type of the external source being accessed by the external functions (there may be a single external source per data service) and its connection properties. When data sources are not included, the data service is designated as a user-defined view, and no connection information is required.

A data service may also define another form of XQuery functions known as private functions. The following types of data source data services are supported:

- Relational
- Web service
- Java function
- Delimited content
- XML content

The following sections describe the data access annotation for the data service types, as well as for data services that are designated as user-defined views. You can specify only one of the annotations in each data service. If no annotation is provided, the data service is considered a user-defined view.

### Relational Data Service Annotations

The data access annotation for a relational data service consists of the empty element `relationalDB` with a single required attribute, name, whose value should be set to the JNDI name by which the external relational source has been registered with the application server. For example:

>     <relationalDB name="OracleDS"/>

In addition, the `relationalDB` element can contain the following optional parts:

- An optional element, named `properties`, that exposes the values of specific settings of the Relational Database Management System (RDBMS) represented by the relational source.
- An optional attribute, named `sourceBindingProviderClassName`, that specifies the transformation used to determine the relational source that should be used at system runtime in the place of the statically defined source.

#### Native Relational Properties

The `properties` element is an empty element with several required and optional attributes, as outlined in Table 5-2.

Table 5-2 Attributes for the properties Element

Attribute | Description
--- | ---
catalogSeparator | Specifies the string used by the RDBMS as a separator between a catalog and a table name. Required.
identifierQuote | Specifies the string used by the RDBMS to quote SQL identifiers. Required.
catalogQuote | Specifies the string used by the RDBMS to quote database catalog identifiers. Optional.
schemaQuote | Specifies the string used by the RDBMS to quote database schema identifiers. Optional.
tableQuote | Specifies the string used by the RDBMS to quote table identifiers. Optional.
columnQuote | Specifies the string used by the RDBMS to quote column identifiers. Optional.
nullSortOrder | A string specifying how null values are sorted by the RDBMS, from among the following values: high, low, or unknown. Required.
supportsCatalogsInDataManipulation | A Boolean specifying whether the RDBMS supports catalog names in Data Manipulation Language (DML) SQL statements. Required.
supportsLikeEscapeClause | A Boolean specifying whether the RDBMS supports LIKE escape clauses. Required.
supportsSchemasInDataManipulation | A Boolean specifying whether the RDBMS supports schema names in DML SQL statements. Required.

#### Source Binding Provider

The value of the optional `sourceBindingProviderClassName` attribute should be bound to the fully-qualified name of a user-defined Java class implementing the `com.bea.ld.bindings.SourceBindingProvider` interface, defined by the following:

>     package com.bea.ld.bindings;
>     public interface SourceBindingProvider
>     {
>     	public String getBinding(String genericLocator, boolean isUpdate);
>     }

The user-defined implementation should provide the transformation that, given the statically configured relational source name (parameter `genericLocator`) and a Boolean flag indicating whether the relational source is accessed in query or update mode (parameter `isUpdate`), determines the name of the relational source name used by the system at runtime.

Note that you can use this transformation mechanism to perform credential mapping. In this case, a single set of query or update operations to be performed in the name of two distinct users U1 and U2 against the same statically-configured relational source R0, is executed against two distinct relational sources R1 and R2 respectively (where all sources R0, R1, R2 represent the same RDBMS and the security policies applied to the connection credentials used for R1 and R2 correspond to the security policies applied to the application credentials of user U1 and U2 respectively).

Note: You should set the source binding provider name uniformly across all relational data services sharing the same relational source JNDI name. Although this restriction is not enforced, its violation could result in unpredictable behavior at runtime.

### Web Service Data Service Annotations

The data access annotation for a data service based on a Web service consists of the empty element `webService` with two required attributes, described in Table 5-3.

Table 5-3 Required Attributes for the webService Element

Attribute | Description
--- | ---
wsdl | A valid `http:` or `ld:` URI pointing to the location of the WSDL file containing the definition of the external Web service source.
targetNamespace | A valid URI that is identical to the `targetNamespace` URI of the WSDL.

For example:

>     <webService targetNamespace="urn:GoogleSearch"
>     	wsdl="ld:google/GoogleSearch.wsdl"/>

### Java Function Data Service Annotations

The data access annotation for a Java function data service consists of the empty element `javaFunction` with a single required attribute named class, whose value should be set to the fully qualified name of the Java class serving as the external source. For example:

>     <javaFunction class="com.example.Test"/>

### Delimited Content Data Service Annotations

The data access annotation for a delimited content data service is the empty element `delimitedFile`, accepting the optional attributes described in Table 5-4.

Table 5-4 Optional Attributes for the delimitedFile Element

Attribute | Description
--- | ---
file | A valid URI pointing to the location of the delimited file.
schema | A valid URI pointing to the location of the XML schema file defining the type (structure) of the delimited contents. If absent, the schema is derived based on the contents.
inferredSchema | Specifies whether the schema was inferred or provided by the user. The default value is false.
delimiter | The string used as the delimiter. If absent, the `fixedLength` attribute should be present.
fixedLength | The fixed length of the tokens contained in fixed length content. If absent, the delimiter attribute should be present.
hasHeader | A Boolean flag indicating whether the first line of the content should be interpreted as a header. The default value is false.

For example:

>     <delimitedFile schema="ld:df/schemas/ALL_TYPES.xsd" hasHeader="true"
>     	delimiter="," file="ld:df/ALL_TYPES.csv"/>

### XML Content Data Service Annotations

The data access annotation for an XML content data service is the empty element `xmlFile` accepting the attributes described in Table 5-5.

Table 5-5 Attributes for the xmlFile Element

Attribute | Description
--- | ---
file | (Optional) A valid URI pointing to the location of the XML file.
schema | A valid URI pointing to the location of the XML schema file defining the type (structure) of the XML contents.

For example:

>     <xmlFile schema="ld:xml/somewhere/CUSTOMER.xsd"
>     	file="ld:xml/CUSTOMER_NESTED.xml"/>

### User Defined View XDS Annotations

The data access annotation for a user-defined view data service is also known as a logical data service. It consists of the single empty element userDefinedView. For example:

>     <userDefinedView/>

## Target Type Properties

The optional block of target type properties enables you to annotate simple valued fields in the target type of the data service with native type information pertaining to the following:

- The type of the corresponding field in the underlying external source (applicable only to data source data services)
- Information about the field's properties with respect to its update behavior. Each annotated field is represented by the element `field` with two required attributes, described in Table 5-6.

Table 5-6 Required Attributes for the field Element

Attribute | Description
--- | ---
xpath | An XPath value pointing to the field
type | The qualified name of the field's simple XML schema or XQuery type.

The following excerpt provides an example of a `field` element definition:

>     <field type="xs:string" xpath="FIRST_NAME">
>     	<extension nativeSize="64" nativeTypeCode="12" nativeType="VARCHAR2"
>     		nativeXpath="FIRST_NAME"/>
>     	<properties nullable="false"/>
>     </field>

### Native Type Properties

Each `field` element can contain an optional `extension` element that accepts the optional attributes described in Table 5-7.

Table 5-7 Optional Attributes for the extension Element

Attribute | Description
--- | ---
nativeXpath | A native XPath value pointing to the corresponding native field in the external source.
nativeType | The native name of the native type of the corresponding native field, as it is known to the external source.
nativeTypeCode | The native type code of the native type of the corresponding native field, as it is known to the external source. In the case of relational sources, this is the type code as reported by JDBC.
nativeSize | The native size of the native type of the corresponding native field, as it is known to the external source. In the case of relational sources, this is the size as reported by JDBC.
nativeFractionalDigits | The native scale of the native type of the corresponding native field, as it is known to the external source. In the case of relational sources, this is the scale as reported by JDBC.

### Update-related Type Properties

Each `field` element can also contain an optional `properties` element that accepts the optional attributes described in Table 5-8.

Table 5-8 properties element Optional Attributes

Attribute | Description
--- | ---
immutable | A Boolean value specifying whether the field is immutable (read-only) or not. The default value is false.
nullable | A Boolean value specifying whether the field accepts null values or not. The default value is false.

## Key Properties

The optional block of key properties enables you to specify a set of identity constraints (keys) on the data service target type. Each key is represented by the element key that accepts an optional attribute, named name, whose value should serve as an identifier for the key.

Each key element contains a sequence of one or more `field` elements that collectively specify the simple-valued target type fields that the key comprises. Keys may be simple (having one field) or compound (having multiple fields). Each `field` element is identified by the value of its required xpath attribute (behaving similarly to the `xpath` attribute described in Target Type Properties on page 5-11).

Furthermore, each `field` element may optionally contain an extension element carrying a `nativeXpath` attribute that behaves similarly to the `nativeXpath` attribute described in Native Properties on page 5-25.

The following excerpt provides an example of a key element definition:

>     <key name="CUSTOMER_PK11015727676593">
>     	<field xpath="CUSTOMER_ID">
>     		<extension nativeXpath="CUSTOMER_ID"/>
>     	</field>
>     </key>

## Relationship Properties

The optional block of relationship properties enables you to specify a set of relationship targets. A relationship target of a data service is a data service with which first service maintains a unidirectional or bidirectional relationship. Unidirectional relationships are realized through one or more navigate functions in the first data service that returns one or more instances of objects of the second service target type. Bidirectional relationships require that reciprocal functions are present in the second data service as well.

A relationship target is represented by the element `relationshipTarget` that accepts the attributes described in Table 5-9.

Table 5-9 Attributes for the relationshipTarget Element

Attribute | Description
--- | ---
roleName | A string that uniquely identifies the relationship target inside the data service.
roleNumber | (Optional) Either 1 or 2 (default is 1). The roleNumber specifies the index of the relationship target within the relationship.
XDS | The Data Services Platform URI of the data service serving as the relationship target.
minOccurs | (Optional) The minimum cardinality of relationship target instances participating in this relationship. Possible values are all non-negative integers and the empty string. The default value is the empty string.
maxOccurs | (Optional) The maximum cardinality of relationship target instances participating in this relationship. Possible values are all positive integers, the string `unbounded`, and the empty string. The default is the empty string.
opposite | (Optional) String attribute that indicates the reciprocal relationship target in the case of bidirectional relationships. The value of this attribute is the identifier used to identify this data service as a relationship target in the data service identified by the value of the XDS attribute.

Additionally, the `relationshipTarget` element can itself contain the element `relationship` which in turn contains the nested element `description` that contains a human readable description about the relationship.

The following excerpt provides an example of a `relationshipTarget` element definition:

>     <relationshipTarget roleName="CUSTOMER_ORDER" roleNumber="2"
>     	XDS="ld:oracleDS/CUSTOMER_ORDER.xds" minOccurs="0"
>     	maxOccurs="unbounded" opposite="CUSTOMER"/>

## Update Properties

The optional block of update properties enables you to specify a set of properties that establish certain policies about updating a data service's underlying sources. In particular, you can specify the following policies:

- The data service function that should be analyzed in order to build the plan for update decomposition.
- The external Java function to use as an update exit.
- The fields to use for optimistic locking purposes.
- Whether the data service is updateable or not.

### Function for Update Decomposition

You can expose data obtained through data service read functions as SDO objects that can later be updated. In order for the changes to be persisted in the original data sources, the data service should specify which read function are to be used to perform data lineage analysis. The result of this analysis is a plan that allows the update to be decomposed into subplans that can be applied on each of the underlying sources. This feature is primarily used by logical data services.

The function for update decomposition is represented by the element `functionForDecomposition` that accepts the required attributes described in Table 5-10.

Table 5-10 Required Attributes for the functionForDecomposition Element

Attribute | Description
--- | ---
name | The qualified name of the read function to be used for update decomposition.
parity | The number of parameters of the read function specified in the `name` attribute.

When the `functionForDecomposition` element is not present, the first read function in the data service document is designated as the function for the update decomposition.

The following excerpt provides an example of a `functionForDecomposition` element definition:

>     <functionForDecomposition xmlns:f="ld:view/myView"
>     	name="f:firstNameFilter" arity="0"/>

### Java Update Exit

A data source data service that is not automatically updateable (all non-relational XDS), or a data view XDS may specify an external mechanism to use for update. Supported external mechanisms include Java classes that implement a particular interface specified in the SDO update specification.

The Java class to use as update exit is represented by the empty element `javaUpdateExit` that accepts the attributes described in Table 5-11.

Table 5-11 Attributes for the javaUpdateExit Element

Attribute | Description
--- | ---
className | The fully qualified name of the Java class.
classFile | (Optional) The LD URI to the Java file for the class.

The following excerpt provides an example of a functionForDecomposition element definition:

>     <javaUpdateExit className="com.example.Exit"/>

### Optimistic Locking Fields

SDO update assumes optimistic locking transactional semantics. The data service being updated can specify the fields that should be checked for updates during the interim using the empty element `optimisticLockingFields` that accepts one of the following as its content:

- An empty element, named `updated`, to specify only updated fields.
- An empty element, named `projected`, to specify all projected fields.
- One or more elements, named `field`, that accept a required string-valued attribute named name to specify user-specified fields.

The following excerpt provides an example of a `functionForDecomposition` element definition:

>     <optimisticLockingFields>
>     	<updated/>
>     </optimisticLockingFields>

### Read-Only Data Service

You can designate a data service as read-only, in which case no updates will be allowed against the results obtained from the read functions of the service. You can use the empty element `readOnly` to designate a data service as read-only. For example:

>     <readOnly/>

## Security Properties

You can use a data service to define one or more user-defined, logical protected resources. The element `secureResources`, containing one or more string-valued elements named `secureResource`, can be used for this purpose.

For example:

>     <secureResources>
>     	<secureResource>MyResource</secureResource/>
>     	<secureResource>MyOtherResource</secureResource/>
>     </secureResources>

You can link a logical resource defined using this syntax to a user-provided security policy using the DSP Console. Query content can inquire about a user's ability to access a logical resource using the built-in function `isAccessAllowed()`.

# XFL Annotations

There is a single XFL annotation per XFL document, which appears before any function annotation in the document. The identifier for the pragma carrying the XFL annotation is `xfl`. The qualified name of the top level element of the XML fragment corresponding to an XFL annotation has the local name `xfl` and the namespace URI `urn:annotations.ld.bea.com`.

The contents of the top-level `xfl` element is a sequence of the following blocks of properties.

- General Properties
- Data Access Properties

The following sections provide detailed descriptions of each block of properties, while the following excerpt provides an example of a XFL annotation, which may serve as a reference.

>     (::pragma xfl <x:xfl xmlns:x="urn:annotations.ld.bea.com">
>     <creationDate>2005-03-09T17:48:58</creationDate>
>     <webService targetNamespace="urn:GoogleSearch"
>     	wsdl="ld:google/GoogleSearch.wsdl"/>
>     </x:xfl>::)

## General Properties

The general properties applicable to an XFL document are identical to the general properties for a data service document, as described in General Properties on page 5-4.

## Data Access Properties

Each XFL document defines one or more XQuery functions that serve as library functions that can be used either inside data service documents to define read navigate or private functions, or inside other XFL documents to specify other library functions.

Since XFL documents do not have a target type, the return types of the library functions found inside these document may differ from each other. In particular, a function inside an XFL document may return a value having a simple type (or any other type). XFL functions can be external data source functions or user-defined.

The following types of XFL documents are supported:

- Relational (logical)
- Web service (logical)
- Java function (logical)
- User-defined view (logical)

You can specify only one of the annotations in each XFL. If no annotation is provided, the XFL is considered a user-defined view.

The data access properties for Relational, Web service, Java function, and user-defined view XFL documents are the same as the corresponding properties for data service documents, as described above.

# Function Annotations

There is a single function annotation per data service or XFL function, which appears before the function declaration in the document. The identifier for the pragma carrying the function annotation is `function`. The qualified name of the top level element of the XML fragment corresponding to an XDS or XFL annotation has the local name `function` and the namespace URI `urn:annotations.ld.bea.com`.

Each data service function is classified using one of the following categories:

- Read function
- Navigate function
- Private function

The classification of an data service function is determined by the value of a required attribute kind in the `function` element, which accepts the values `read`, `navigate`, or `private` to denote the corresponding categories. Each XFL function is considered to be a library function.

The prime type of the return type of a read function must match the target type of the data service. In addition, the `function` element for a navigate function must carry a string-valued attribute `returns` whose value must match the role name of a relationship target defined in the data service. Moreover, the prime type of the return type of a navigate function must match the target type of the data service serving as the relationship target.

Finally, the namespace URIs of the qualified names of all the functions in a data service or XFL must specify the location of the data service or XFL document in the LD repository. For example:

>     ld:{directory path to data service folder}/{data service file name without extension}

or

>     lib:{directory path to XFL folder}/{XFL file name without extension}

The `function` element accepts the additional optional attributes described in Table 5-12.

Table 5-12 Optional Attributes for the function Element

Attribute | Description
--- | ---
nativeName | Applicable to data source functions, `nativeName` is the name of the function as it is known to the external source. In the case of relational sources, for example, it corresponds to the table name.
nativeLevel1Container | Applicable to data source functions that represent external sources employing hierarchical containment schemes; `nativeLevel1Container` is the name of the top-level native container, as it is known to the external source. In the case of relational sources, for example, it corresponds to the catalog name, whereas, in the case of Web service sources, it corresponds to the service name.
nativeLevel2Container | Applicable to data source functions that represent external sources employing hierarchical containment schemes; `nativeLevel2Container` is the name of the second-level native container, as it is known to the external source. In the case of relational sources, for example, it corresponds to the schema name. In the case of Web service sources, it corresponds to the port name.
nativeLevel3Container | Applicable to data source functions that represent external sources employing hierarchical containment schemes; `nativeLevel3Container` is the name of the top-level native container, as it is known to the external source. In the case of relational sources, for example, it corresponds to the stored procedure package name.
style | Applicable to data source functions, `style` is a native qualifier by which the function is known to the external source (e.g. table, view, storedProcedure, or sqlQuery for relational sources; rpc or document for Web services).
roleName | Applicable to navigate functions, `roleName` should match the value of the `roleName` attribute of the relationshipTarget implemented by the function.

The content of the top-level function element is a sequence of the following blocks of properties:

- General Properties
- UI Properties
- Cache Properties
- Signature Properties
- Native Properties

The following excerpt provides an example of a function annotation:

>     (::pragma function <f:function xmlns:f="urn:annotations.ld.bea.com" kind="datasource" nativeName="CUSTOMER" nativeLevel2Container="RTL" style="table">
>     <cacheable>
>     	<useCache TTL="600"/>
>     </cacheable>
>     </f:function>::)

## General Properties

All standard document properties and user-defined properties defined in Standard Document Properties on page 5-4 and User-Defined Properties on page 5-4 are applicable to function annotations.

## UI Properties

A set of user interface properties may be introduced by the XQuery Editor to persist location information about the graphical components representing the expression in the function body. UI properties are represented by the element `uiProperties` which accepts a sequence of one or more elements, named component, as its content. Each component element accepts the attributes described in Table 5-13

Table 5-13 Attributes for the component Element

Attribute | Description
--- | ---
identifier | An identifier for the UI component.
minimized | A Boolean flag indicating whether the UI component has been minimized or not.
x | The x-coordinate for the UI component.
y | The y-coordinate for the UI component.
w | The width of the UI component.
h | The height of the UI component.
viewPosX | The x-coordinate of the scrollbar position of the component.
viewPosY | The y-coordinate of the scrollbar position of the component.

In addition, each `component` element may optionally contain one or more `treeInfo` elements containing information about the tree representation of the types pertaining to the component. In the absence of the above property, the query editor uses the default layout.

## Cache Properties

You can use the optional block of cache properties to specify whether a function can be cached or not. You should specify a function whose results for the same set of arguments are intrinsically highly volatile as non-cached. On the other hand, you should specify a function whose results for the same set of arguments are either fixed or remain unchanged for a period of time as cacheable.

This property of a function is represented by the empty element `nonCacheable`. In the absence of the `nonCacheable` element, a function is considered to be potentially cacheable. The following excerpt provides an example:

>     <nonCacheable/>

## Signature Properties

You can use the optional block of signature properties to annotate the parameters of a data service or XFL function with additional information to that provided by the function signature. These properties are applicable to data source (data service or XFL) functions.

The signature properties block is represented by the element `params` which accepts a sequence of one or more elements, named `param`, as its content. Each `param` element is an empty element that accepts the optional attributes described in Table 5-14.

Table 5-14 param element Optional Attributes

Attribute | Description
--- | ---
name | The name of the parameter, as it is known to the external source.
nativeType | The native type of the parameter, as it is known to the external source.
nativeTypeCode | The native type code of the parameter, as it is known to the external source.
xqueryType | The qualified name of the XML Schema or XQuery type used for the parameter.
kind | One of the following values: unknown, in, inout, out, return or result (applicable to stored procedures).

The following excerpt provides an example of a params element definition:

>     <params>
>     	<param nativeType="java.lang.String"/>
>     	<param nativeType="java.lang.int"/>
>     </params>

## Native Properties

You can use native properties to further annotate a data source function based on the type of the external source that it represents. There are two types of native properties pertaining to relational and Web service sources respectively:

- SQL query properties
- SOAP handler properties

### SQL Query Properties

The `function` annotation element of a function that represents a user-defined SQL query has its style attribute set to `sqlQuery` and accepts a nested element, named `sql`. The `sql` element accepts string content that corresponds to the statement of the (possibly parameterized) SQL query that the function represents.

If required, the statement can be escaped inside a CDATA section to account for reserved XML characters (e.g. <, >, &). The `sql` element also accepts the optional attribute `isSubquery` whose boolean value indicates whether the SQL statement may be used as a nested SQL sub-query. If the attribute is absent, its value defaults to `true`.

The following excerpt provides an example of a `sqlQuery` element definition:

>     <sql isSubquery="true">
>     	SELECT t.FIRST_NAME FROM RTLALL.dbo.CUSTOMER t</sql>

### SOAP Handler Properties

The `function` annotation element of a function that represents a Web service call accepts a nested element, named `interceptorConfiguration`. The `interceptorConfiguration` element accepts two required attributes, as described in Table 5-15.

Table 5-15 Required Attributes for the interceptorConfiguration Element

Attribute | Description
--- | ---
fileName | The location of the file containing the configuration of the SOAP handler chains that are applicable to the Web service.
aliasName | The alias name by which the SOAP handler chain has been configured.