| Abstract: | This specification defines a backwards-compatible extension to the XMPP Data Forms protocol that enables applications to specify additional validation guidelines related to a form, such as validation of standard XML datatypes, application-specific datatypes, value ranges, and regular expressions. |
| Author: | Matthew Miller |
| Copyright: | © 1999 – 2017 XMPP Standards Foundation. SEE LEGAL NOTICES. |
| Status: | Draft |
| Type: | Standards Track |
| Version: | 1.0.2 |
| Last Updated: | 2018-03-21 |
NOTICE: The protocol defined herein is a Draft Standard of the XMPP Standards Foundation. Implementations are encouraged and the protocol is appropriate for deployment in production systems, but some changes to the protocol are possible before it becomes a Final Standard.
1. Introduction
2. Requirements
3. Use Cases
3.1. Datatype Validation
3.2. Validation Methods
3.2.1. <basic/> Validation
3.2.2. <open/> Validation
3.2.3. <range/> Validation
3.2.4. <regex/> Validation
3.3. Selection Ranges in "list-multi"
4. Implementation Notes
4.1. Required to Support
4.2. Namespacing
4.3. Internationalization/Localization
4.4. Form Submissions
4.5. Existing Protocols
4.6. Display Considerations
4.7. Validation Ranges
5. Security Considerations
6. IANA Considerations
7. XMPP Registrar Considerations
7.1. Protocol Namespaces
7.2. Registries
7.2.1. Datatype Prefixes Registry
7.2.1.1. Process
7.2.1.2. Initial Submission
7.2.2. Datatypes Registry
7.2.2.1. Process
7.2.2.2. Initial Submission
8. XML Schema
Appendices
A: Document Information
B: Author Information
C: Legal Notices
D: Relation to XMPP
E: Discussion Venue
F: Requirements Conformance
G: Notes
H: Revision History
Data Forms (XEP-0004) [1] ("x:data") provides a simple and interoperable way to request and present information for both applications and humans. However, the simple nature of "x:data" requires the form interpreter at times to guess as to exactly what type of information is being requested or provided. This document builds upon "x:data" to provide this additional validation.
The requirements for this document are:
This document defines a new namespace, "http://jabber.org/protocol/xdata-validate". The root element for this namespace is <validate/>, and MUST be contained within a <field/> element (qualified by the 'jabber:x:data' namespace) for each Data Forms field that possesses additional validation information.
The simplest usage is to provide a more-granular datatype for a <field/> element used in Data Forms. To provide this datatype information, a <validate/> element is included whose 'datatype' attribute specifies the data type of any <value/> contained within the <field/> element:
Example 1. Field with extended datatype
<field var='evt.date' type='text-single' label='Event Date/Time'>
<validate xmlns='http://jabber.org/protocol/xdata-validate'
datatype='xs:dateTime'/>
<value>2003-10-06T11:22:00-07:00</value>
</field>
The preceding example demonstrates a field that is expected to contain a date/time value.
The 'datatype' attribute specifies the datatype. This attribute is OPTIONAL, and defaults to "xs:string". It MUST meet one of the following conditions:
Note that while "x:" allows for ad-hoc definitions, its use is NOT RECOMMENDED.
In addition to datatypes, the validation method can also be provided. The method is specified via a child element. The validation methods defined in this document are:
If no validation method is specified, form processors MUST assume <basic/> validation. The <validate/> element SHOULD include one of the above validation method elements, and MUST NOT include more than one.
Any validation method applied to a field of type "list-multi", "list-single", or "text-multi" (other than <basic/>) MUST imply the same behavior as <open/>, with the additional constraints defined by that method.
Building upon the earlier example, to indicate that the value(s) should simply match the field type and datatype constraints, the <validate/> element shall contain a <basic/> child element.
<field var='evt.date' type='text-single' label='Event Date/Time'>
<validate xmlns='http://jabber.org/protocol/xdata-validate'
datatype='xs:dateTime'>
<basic/>
</validate>
<value>2003-10-06T11:22:00-07:00</value>
</field>
Using <basic/> validation, the form interpreter MUST follow the validation rules of the datatype (if understood) and the field type.
For "list-single" or "list-multi", to indicate that the user may enter a custom value (matching the datatype constraints) or choose from the predefined values, the <validate/> element shall contain an <open/> child element:
<field var='evt.category'
type='list-single'
label='Event Category'>
<validate xmlns='http://jabber.org/protocol/xdata-validate'
datatype='xs:string'>
<open/>
</validate>
<option><value>holiday</value></option>
<option><value>reminder</value></option>
<option><value>appointment</value></option>
</field>
The <open/> validation method applies to "text-multi" differently; it hints that each value for a "text-multi" field shall be validated separately. This effectively turns "text-multi" fields into an open-ended "list-multi", with no options and all values automatically selected.
To indicate that the value should fall within a certain range, the <validate/> element shall contain a <range/> child element:
<field var='evt.date' type='text-single' label='Event Date/Time'>
<validate xmlns='http://jabber.org/protocol/xdata-validate'
datatype='xs:dateTime'>
<range min='2003-10-05T00:00:00-07:00'
max='2003-10-24T23:59:59-07:00'/>
</validate>
<value>2003-10-06T11:22:00-07:00</value>
</field>
The 'min' and 'max' attributes of the <range/> element specify the minimum and maximum values allowed, respectively.
The 'max' attribute specifies the maximum allowable value. This attribute is OPTIONAL. The value depends on the datatype in use.
The 'min' attribute specifies the minimum allowable value. This attribute is OPTIONAL. The value depends on the datatype in use.
The <range/> element SHOULD possess either a 'min' or 'max' attribute, and MAY possess both. If neither attribute is included, the processor MUST assume that there are no range constraints.
To indicate that the value should be restricted to a regular expression, the <validate/> element shall contain a <regex/> child element:
Example 5. Regular expression validation
<field var='ssn' type='text-single' label='Social Security Number'>
<desc>This field should be your SSN, including '-' (e.g. 123-12-1234)</desc>
<validate xmlns='http://jabber.org/protocol/xdata-validate'
datatype='xs:string'>
<regex>([0-9]{3})-([0-9]{2})-([0-9]{4})</regex>
</validate>
</field>
The XML character data of this element is the pattern to apply. The syntax of this content MUST be that defined for POSIX extended regular expressions [4], including support for Unicode [5].
The <regex/> element MUST contain character data only.
For "list-multi", validation can indicate (via the <list-range/> element) that a minimum and maximum number of options should be selected and/or entered. This selection range MAY be combined with the other methods to provide more flexibility.
Example 6. Selection Range validation
<field var='evt.notify-methods'
type='list-multi'
label='Notify me by'>
<validate xmlns='http://jabber.org/protocol/xdata-validate'
datatype='xs:string'>
<basic/>
<list-range min='1' max='3'/>
</validate>
<option><value>e-mail</value></option>
<option><value>jabber/xmpp</value></option>
<option><value>work phone</value></option>
<option><value>home phone</value></option>
<option><value>cell phone</value></option>
</field>
The <list-range/> element SHOULD be included only when the <field/> is of type "list-multi" and SHOULD be ignored otherwise.
The 'max' attribute specifies the maximum allowable number of selected/entered values. This attribute is OPTIONAL. The value MUST be a positive integer.
The 'min' attribute specifies the minimum allowable number of selected/entered values. This attribute is OPTIONAL. The value MUST be a positive integer.
The <list-range/> element SHOULD possess either a 'min' or 'max' attribute, and MAY possess both. If neither attribute is included, the processor MUST assume that there are no selection constraints.
At a minimum, implementations MUST support the following:
If an implementation does not understand the specified datatype, it MUST validate according to the default "xs:string" datatype. If an implementation does not understand the specified method, it MUST validate according to the <basic/> method.
While all elements associated with this document MUST be qualified by the 'http://jabber.org/protocol/xdata-validate' namespace, explicitly declaring the default namespace for each instance can be overly verbose. However, Jabber/XMPP implementations have historically been very lax regarding namespacing, thus requiring some careful use of prefixes.
The use of namespace prefixes is RECOMMENDED for large forms, to reduce the data size. To maintain the highest level of compatibility, implementations sending the form using prefixes SHOULD use the namespace prefix "xdv", and SHOULD declare the namespace prefix mapping in the ancestor <x xmlns='jabber:x:data'/> element:
Example 7. Example of recommended namespace prefixing
<x xmlns='jabber:x:data'
xmlns:xdv='http://jabber.org/protocol/xdata-validate'
type='form'>
<title>Sample Form</title>
<instructions>
Please provide information for the following fields...
</instructions>
<field type='text-single' var='name' label='Event Name'/>
<field type='text-single' var='date/start' label='Starting Date'>
<xdv:validate datatype='xs:date'>
<basic/>
</xdv:validate>
</field>
<field type='text-single' var='date/end' label='Ending Date'>
<xdv:validate datatype='xs:date'>
<basic/>
</xdv:validate>
</field>
</x>
This document relies on the internationalization/localization mechanisms provided by XMPP Core [6]. As much as possible, all datatype formats MUST be locale-independent.
Form processors MUST NOT assume that a form with validation has actually been validated when submitted. There is no realistic expectation that form interpreters honor validation.
While this document is compatible with the existing "x:data" definition, form providers SHOULD first determine support for it, using either Entity Capabilities (XEP-0115) [7] if presence-aware or Service Discovery (XEP-0030) [8]. This is especially important for limited-connection and/or limited-capabilities devices, such as cell phones.
Although primarily intended for validating form submission, validation MAY have an impact on display, and MAY be applied to data forms that are not submitted (e.g. 'result' type forms). The following table outlines which field types a particular validation method is or is not appropriate for, and how a display SHOULD interpret the validation methods if considered [9]:
Table 1: Validation Methods and Field Types
| Validation Method | SHOULD be Allowed | SHOULD NOT be Allowed | Display Suggestions |
|---|---|---|---|
| basic |
|
|
Display the datatype appropriate to the locale |
| open |
|
|
Display the datatype appropriate to the locale. For "text-multi" treat each value as a discrete entry (e.g. a user-entered list). For "list-multi" or "list-single", allow user to add/remove entries to select. |
| range |
|
|
Display the datatype appropriate to the locale. For "text-single", allow user to increment/decrement through possible values. For "text-multi" treat each value as a discrete entry (e.g. a user-entered list). For "list-multi" or "list-single", allow user to add/remove entries to select. |
| regex |
|
|
Display the datatype appropriate to the locale. If possible, display a valid example. For "text-multi" treat each value as a discrete entry (e.g. a user-entered list). For "list-multi" or "list-single", allow user to add/remove entries to select. |
The <range/> validation method MUST be used only with datatypes that have finite quantities. Within the standard datatype set, it MUST NOT be used with "xs:string".
This document introduces no security concerns above and beyond those specified in XEP-0004: Data Forms.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [10].
The XMPP Registrar includes 'http://jabber.org/protocol/xdata-validate' in its registry of protocol namespaces.
The XMPP Registrar maintains a registry of datatype prefixes used in the context of Data Forms Validation (see <https://xmpp.org/registrar/xdv-prefixes.html>), where each prefix denotes a group of related datatypes.
In order to submit new values to this registry, the registrant shall define an XML fragment of the following form and either include it in the relevant XMPP Extension Protocol or send it to the email address <registrar@xmpp.org>:
<datatype-prefix> <prefix>the prefix token (e.g., "xs")</prefix> <desc>a natural-language description of the datatype family</desc> <doc>the document in which datatype family is specified</doc> </datatype-prefix>
The registrant may register more than one prefix at a time, each contained in a separate <datatype-prefix/> element.
As part of this document, the following datatype prefixes shall be registered:
<datatype-prefix> <prefix>x</prefix> <desc>An ad-hoc datatype</desc> <doc>XEP-0122</doc> </datatype-prefix> <datatype-prefix> <prefix>xs</prefix> <desc>A "standard" datatype as defined in XML Schema Part 2</desc> <doc>XML Schema Part 2</doc> </datatype-prefix>
The XMPP Registrar maintains a registry of datatypes used in the context of Data Forms Validation (see <https://xmpp.org/registrar/xdv-datatypes.html>), where each datatype name includes the relevant prefix (e.g., "xs:anyURI").
In order to submit new values to this registry, the registrant shall define an XML fragment of the following form and either include it in the relevant XMPP Extension Protocol or send it to the email address <registrar@xmpp.org>:
<datatype> <name>the full datatype name (e.g., "xs:string")</name> <desc>a natural-language description of the datatype</desc> <methods>the validation methods that may apply to the datatype</methods> <min>the minimum value for the datatype (if any)</min> <max>the maximum value for the datatype (if any)</max> </datatype>
The registrant may register more than one datatype at a time, each contained in a separate <datatype/> element.
The following submission contains the built-in datatypes defined in XML Schema Part 2 that are deemed mostly like to be useful in the context of the Data Forms protocol; additional datatypes defined therein, as well as other datatypes not defined in XML Schema Part 2, may be registered via separate submissions in the future.
<datatype> <name>xs:anyURI</name> <desc>a Uniform Resource Identifier Reference (URI)</desc> <methods>basic regex</methods> <min>N/A</min> <max>N/A</max> </datatype> <datatype> <name>xs:byte</name> <desc>an integer with the specified min/max</desc> <methods>basic range</methods> <min>-128</min> <max>127</max> </datatype> <datatype> <name>xs:date</name> <desc>a calendar date</desc> <methods>basic range regex</methods> <min>N/A</min> <max>N/A</max> </datatype> <datatype> <name>xs:dateTime</name> <desc>a specific instant of time</desc> <methods>basic range regex</methods> <min>N/A</min> <max>N/A</max> </datatype> <datatype> <name>xs:decimal</name> <desc>an arbitrary-precision decimal number</desc> <methods>basic range</methods> <min>none</min> <max>none</max> </datatype> <datatype> <name>xs:double</name> <desc>an IEEE double-precision 64-bit floating point type</desc> <methods>basic range</methods> <min>none</min> <max>none</max> </datatype> <datatype> <name>xs:int</name> <desc>an integer with the specified min/max</desc> <methods>basic range</methods> <min>-2147483648</min> <max>2147483647</max> </datatype> <datatype> <name>xs:integer</name> <desc>a decimal number with no fraction digits</desc> <methods>basic range</methods> <min>none</min> <max>none</max> </datatype> <datatype> <name>xs:language</name> <desc>a language identifier as defined by RFC 1766</desc> <methods>basic regex</methods> <min>N/A</min> <max>N/A</max> </datatype> <datatype> <name>xs:long</name> <desc>an integer with the specified min/max</desc> <methods>basic range</methods> <min>-9223372036854775808</min> <max>9223372036854775807</max> </datatype> <datatype> <name>xs:short</name> <desc>an integer with the specified min/max</desc> <methods>basic range</methods> <min>-32768</min> <max>32767</max> </datatype> <datatype> <name>xs:string</name> <desc>a character strings in XML</desc> <methods>basic regex</methods> <min>N/A</min> <max>N/A</max> </datatype> <datatype> <name>xs:time</name> <desc>an instant of time that recurs every day</desc> <methods>basic range regex</methods> <min>N/A</min> <max>N/A</max> </datatype>
<?xml version='1.0' encoding='UTF-8'?>
<xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='http://jabber.org/protocol/xdata-validate'
xmlns='http://jabber.org/protocol/xdata-validate'
elementFormDefault='qualified'>
<xs:element name='validate'>
<xs:complexType>
<xs:sequence>
<xs:choice minOccurs='0' maxOccurs='1'>
<xs:element ref='basic'/>
<xs:element ref='open'/>
<xs:element ref='range'/>
<xs:element ref='regex'/>
</xs:choice>
<xs:element ref='list-range' minOccurs='0' maxOccurs='1'/>
</xs:sequence>
<xs:attribute name='datatype'
type='xs:string'
use='optional'
default='xs:string'/>
</xs:complexType>
</xs:element>
<xs:element name='basic' type='empty'/>
<xs:element name='open' type='empty'/>
<xs:element name='range'>
<xs:complexType>
<xs:simpleContent>
<xs:extension base='empty'>
<xs:attribute name='min' use='optional'/>
<xs:attribute name='max' use='optional'/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element name='regex' type='xs:string'/>
<xs:element name='list-range'>
<xs:complexType>
<xs:simpleContent>
<xs:extension base='empty'>
<xs:attribute name='min'
type='xs:unsignedInt'
use='optional'/>
<xs:attribute name='max'
type='xs:unsignedInt'
use='optional'/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:simpleType name='empty'>
<xs:restriction base='xs:string'>
<xs:enumeration value=''/>
</xs:restriction>
</xs:simpleType>
</xs:schema>
Series: XEP
Number: 0122
Publisher: XMPP Standards Foundation
Status:
Draft
Type:
Standards Track
Version: 1.0.2
Last Updated: 2018-03-21
Approving Body: XMPP Council
Dependencies: XMPP Core, XEP-0004
Supersedes: None
Superseded By: None
Short Name: xdata-validate
Schema: <http://www.xmpp.org/schemas/xdata-validate.xsd>
Registry:
<http://xmpp.org/registrar/xdata-validate.html>
Source Control:
HTML
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XML
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The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.
The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.
Discussion on other xmpp.org discussion lists might also be appropriate; see <http://xmpp.org/about/discuss.shtml> for a complete list.
Errata can be sent to <editor@xmpp.org>.
The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".
1. XEP-0004: Data Forms <https://xmpp.org/extensions/xep-0004.html>.
2. XML Schema Part 2: Datatypes <http://www.w3.org/TR/xmlschema11-2/>.
3. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <https://xmpp.org/registrar/>.
4. The "best" definition of this syntax can be found in the re_format(7) man page
5. Guidelines for adapting regular expressions to support Unicode is defined at http://www.unicode.org/reports/tr18/
6. RFC 6120: Extensible Messaging and Presence Protocol (XMPP): Core <http://tools.ietf.org/html/rfc6120>.
7. XEP-0115: Entity Capabilities <https://xmpp.org/extensions/xep-0115.html>.
8. XEP-0030: Service Discovery <https://xmpp.org/extensions/xep-0030.html>.
9. If a particular field type is not listed, the display MAY include validation support, but is not expected to do so.
10. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.
Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/
END