Abstract
This document describes an XML encoding standard for metadata about IVOA standards themselves, referred to as VOStandard. It is intended to allow for the discovery of a standard via an IVOA identifier that refers to the standard. It also allows one to define concepts that are defined by the standard which can themselves be referred to via an IVOA identifier (augmented with a URL fragment identifier). Finally, it can also provide a machine interpretable description of a standard service interface. We describe the general model for the schema and explain its intended use by interoperable registries for discovering resources.Preface
Status of this document
This is an IVOA Working Draft for review by IVOA members and other interested parties. It is a draft document and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use IVOA Working Drafts as reference materials or to cite them as other than "works in progress".
Comments on this document for consideration in the next version are welcome. They can be sent to registry@ivoa.net, a mailing list with a public archive or on the VOStandard twiki discussion page. When this document becomes a Proposed Recommendation, an official public Request For Comment period will begin.
A list of current IVOA Recommendations and other technical documents can be found at http://www.ivoa.net/Documents/.
- Editor's Note:
- Parts that the editor considers should be removed from the document are marked in red with a strike through line, and sections that need more work are indicated in green.
Acknowledgements
This document has been developed with support from the National Science Foundation's Information Technology Research Program under Cooperative Agreement AST0122449 with The Johns Hopkins University, from the UK Particle Physics and Astronomy Research Council (PPARC), and from the Eurpean Commission's Sixth Framework Program via the Optical Infrared Coordination Network (OPTICON).
This document contains text lifted verbatim, with small changes, and with substantial changes from the previously published VODataService specification [VDS] (e.g. sections 2.0). This has been done without specific attribution as a means for providing consistency across similar documents. We acknowledge the authors of that document for this text.
Conformance-related definitions
The words "MUST", "SHALL", "SHOULD", "MAY", "RECOMMENDED", and "OPTIONAL" (in upper or lower case) used in this document are to be interpreted as described in IETF standard, RFC 2119 [RFC 2119].
The Virtual Observatory (VO) is general term for a collection of federated resources that can be used to conduct astronomical research, education, and outreach. The International Virtual Observatory Alliance (IVOA) is a global collaboration of separately funded projects to develop standards and infrastructure that enable VO applications.
XML document validation is a software process that checks that an XML document is not only well-formed XML but also conforms to the syntax rules defined by the applicable schema. Typically, when the schema is defined by one or more XML Schema [Schema] documents (see next section), validation refers to checking for conformance to the syntax described in those Schema documents. This document describes additional syntax constraints that cannot be enforced solely by the rules of XML Schema; thus, in this document, use of the term validation includes the extra checks that goes beyond common Schema-aware parsers which ensure conformance with this document.
Syntax Notation Using XML Schema
The eXtensible Markup Language, or XML, is document syntax for marking textual information with named tags and is defined by the World Wide Web Consortium (W3C) Recommendation, XML 1.0 [XML]. The set of XML tag names and the syntax rules for their use is referred to as the document schema. One way to formally define a schema for XML documents is using the W3C standard known as XML Schema [Schema].
This document defines the VOStandard schema using XML Schema. The full Schema document is listed in Appendix A. Parts of the schema appear within the main sections of this document; however, documentation nodes have been left out for the sake of brevity.
Reference to specific elements and types defined in the VOResource
schema include the namespaces prefix, vr, as in
vr:Resource (a type defined in the VOResource schema).
Reference to specific elements and types defined in the VOStandard
schema include the namespaces prefix, vstd, as in
vstd:ServiceStandard (a type defined in the VOStandard schema).
Use of the vstd prefix in compliant instance documents is
strongly recommended, particularly in the applications that involve
IVOA Registries (see [RI], section 3.1.2).
Elsewhere, the use is not required.
Contents
Introduction
An important goal of the IVOA is to publish standards for services
which can interoperate to create a Virtual Observatory (VO). Central
to the coordination of these services is the concept of a registry
([RI]) where resources can be described and thus
discovered by users and applications in the VO. The standard
Resource
Metadata for the Virtual Observatory [Hanisch et
al. 2004] (hereafter referred to as RM) defines
metadata terms for services and other discoverable resources. A
specific XML encoding of these resources is described in the IVOA standard
VOResource:
an XML Encoding Schema for Resource Metadata [Plante
et al. 2006] (hereafter refered to as VOResource).
In this schema, support for a standard service protocol is described
as a service's capability; the associated metadata is
contained within the service resource description's
<capability> element. The
specific standard protocol supported is uniquely identified via an
attribute of the <capability> element called
standardID
whose value is a URI. The VOResource standard does
not place a formal validation requirement on the
standardID other than it be a legal URI; however, it
was intended that IVOA-endorsed standards would represented via an
IVOA identifier. As per the IVOA Identifier standard
[ID], an IVOA identifier must be registered as a
resource in an IVOA-compliant registry.
This document defines a VOResource extension schema call VOStandard which allows one to describe a standard and register it with an IVOA registry. By doing so, a unique IVOA identifier becomes "attached" to the standard which can be referred to in other resource descriptions, namely for services that support the standard. Not only does this aid in the unambiguous discovery of complient service instances but also in validating their descriptions and support for the standard. Another benefit of associating an IVOA identifier with a standard is that allows registry users who discover services that conform to particular standard to also discover the document that describes that standard.
VOStandard has two other purposes. First, it allows a service protocol description to communicate specifics about the standard input parameters and output formats specified by the standard. Such a machine-readable description of the interface can assist intelligent portals and applications to build GUI interfaces to standard services and manage workflows built around them. Second, it allows for the definition of small controlled sets of standardized names (referred to as keys in this document) which might be used to identify, for example, specific features of a standard protocol (such as supported data transport protocols). By virtue of being defined within the context of a VOResource description, one can refer to the key using a globally unique URI by adding the key name as a URI fragment [URI] onto IVOA identifier associated with the descriptions.
It is envisaged that VOStandard instances that describe standards
endorsed or otherwise in development by the IVOA will be published in
the IVOA Registry of Registries [RofR] using the
authority identifier [ID], ivoa.net.
However, other standards, be they ad hoc or endorsed by another
body, may be published in any compliant registry.
The VOStandard Data Model
The VOStandard extension in general enables the description of three types of resources:
- a generic standard (specified by an external document)
- a standard specifically defining a service protocol
- a set of related, standardized names called keys.
<ri:Resource xsi:type="vstd:StandardKeyEnumeration" created="2001-12-31T12:00:00"
updated="2001-12-31T12:00:00" status="active">
<title>application languages</title>
<identifier>ivo://ivoa.net/std/application/languages</identifier>
<curation>
<publisher>IVOA</publisher>
<creator>
<name>IVOA</name>
<logo>http://www.ivoa.net/icons/ivoa_logo_small.jpg</logo>
</creator>
<date role="representative">2006-07-17</date>
<version>1.0</version>
<contact>
<name>IVOA Grid and Web Services WG</name>
<email>grid@ivoa.net</email>
</contact>
</curation>
<content>
<subject>IVOA Standard: registry</subject>
<description>
This resource defines keys for commonly used computer languages.
</description>
<referenceURL>http://www.ivoa.net/twiki/bin/view/IVOA/IvoaResReg</referenceURL>
</content>
<key>
<name>C</name>
<description>The C programming language</description>
</key>
<key>
<name>CPP</name>
<description>The C++ programming language</description>
</key>
<key>
<name>CSharp</name>
<description>The C# programming language</description>
</key>
<key>
<name>FORTRAN</name>
<description>The FORTRAN programming language</description>
</key>
<key>
<name>Java</name>
<description>The Java programming language</description>
</key>
<key>
<name>Perl</name>
<description>The Perl programming language</description>
</key>
<key>
<name>Python</name>
<description>The Python programming language</description>
</key>
</ri:Resource>
The Schema Namespace and Location
The namespace associated with VOStandard extensions is "http://www.ivoa.net/xml/VOStandard/v1.0". Just like the namespace URI for the VOResource schema, the VOStandard namespace URI can be interpreted as a URL. Resolving it will return the XML Schema document (given in Appendix A) that defines the VOStandard schema.
Authors of VOResource instance documents may choose to
provide a location for the VOResource XML Schema document and its
extensions using the
xsi:schemaLocation attribute. While the choice of
the location value is the choice of the author, this specification
recommends using the VOStandard namespace URI as its location URL
(as illustrated in the example above), as in,
xsi:schemaLocation="http://www.ivoa.net/xml/VOStandard/v1.0
http://www.ivoa.net/xml/VOStandard/v1.0"
- Note:
- The IVOA Registry Interface standard [RI] actually requires that the VOResource records it shares with other registries provide location URLs via
xsi:schemaLocationfor the VOResource schema and all legal extension schemas that are used in the records. This rule would apply to the VOStandard schema.
The prefix, vstd, is used by convention as the
prefix defined for the VOStandard schema; however, instance documents
may use any prefix of the author's choosing. In applications where
common use of prefixes is recommended (such as with the Registry
Interface specification [RI]), use of the
vstd prefix is recommended. Note also that in this
document, the vr prefix is used to label, as shorthand, a
type or element name that is defined in the VOResource schema, as in
vr:Resource.
As recommend by the VOResource standard [VR], the
VOStandard schema sets elementFormDefault="unqualified".
This means that it is not necessary to qualify element names defined
in this schema with a namespace prefix (as there are no global
elements defined). The only place it is usually needed is as a
qualifier to a VOStandard type name given as the value of an
xsi:type attribute.
Summary of Metadata Concepts
The VOStandard extension defines three new types of resources. Two are specifically for independently documented standards:
vstd:Standard- This resource describes a general standard (e.g. data model, schema, protocol, etc.). The most important piece of metadata associated with this resource is the
<referenceURL>(from the core VOResource schema) which should point to the human-readable specification document that defines the standard. It also allows one to provide the recommended version of the standard to use.vstd:ServiceStandard- This resource type, which extends from
vstd:Standard, is specifically for describing a standard service protocol (e.g. Simple Cone Search). It differs fromvstd:Standardin that it also allows one to describe specific constraints on the service interface via its<interface>element.vstd:StandardKeyEnumeration- This resource type allows for the description of a related set controlled names (referred to as keys) and their meanings. While keys can be defined as part of a
vstd:Standardorvstd:ServiceStandardresource, thevstd:StandardKeyEnumerationallows a set of key definitions stand as a resource on its own, regardless of whether it is part of a documented standard or not.
Defining Enumerations of Identifiers
A common practice when defining metadata to restrict
certain string values to a controlled sets of defined names, each with
a well-defined meaning. With XML
Schema, the controlled set can be enforced by a validating parser
(using the xsd:enumeration construct
[Schema]). One disadvantage of locking in the
vocabulary in an XML Schema document is that growing list of allowed
names requires a revision of the XML Schema document, which can be a
disruptive change. To avoid this, it is the practice VOResource and
its extensions to avoid "hard-coded" enumerations in the XML Schema
document for sets of defined values that will likely change over
time.
The VOStandard schema provides an alternative to XML Schema-based definitions of controlled names. Instead, a controlled list of names, called standard keys, can be defined as part of any of the three VOStandard resource types. Updating a resourse description is much less disruptive than a Schema document, and as a resource available via an IVOA-compliant registry, it is still possible for a (non-Schema-based) application to validate the use of the vocabulary.
The VOStandard specification also defines a mapping from a key name to a URI. This allows these keys--and their underlying meaning--to be referenced in a globally unique way in a variety of contexts, not restricted to XML.
A key is defined using the vstd:StandardKey type which
consists simply of a name and a description. The key is mapped to a
URI by attaching the name as the "fragment"--i.e., appending after a
pound sign, #--to the IVOA identifier for the resource
description that defines the key:
ivoa-identifier#key-name
where ivoa-identifier is the resource's IVOA identifier and key-name is the name of a key defined in that resource.
For example with a key named case-insensitive defined
within a resource description with an IVOA identifier given by
<identifier> ivo://ivoa.net/std/QueryProtocol
<identifier>, the URI identifying this key would be:
ivo://ivoa.net/std/QueryProtocol#case-insensitive
This form of defining multiple keys, each with its own mapping to a URI, all in one resource has several advantages:
- The enumerations are naturally grouped under a single registry resource, and so can be retrieved with one registry query and need no further metadata to assert the association.
- The "Dublin core" metadata that is associated with a resource need only be entered once for the whole enumeration, rather than for each member of the enumeration - this saves both curation effort and space in the registry.
- If it is necessary to expand the list of controlled names (or shrink it), it is simple and fairly undisruptive to update the VOResource record.
- Note:
- When these enumerations are presented to a user in a GUI it is expected that the only the "fragment" part that distinguishes the various members of the enumeration will be used as a choice value, as the full IVO ID is not usually particularly "user-friendly".
Some applications may wish to publish additional metadata associated
with a key definition through further extension of VOResource
metadata. This can be be done by deriving a new key metadatum type
derived by extension from the vstd:StandardKey.
The VOStandard Metadata
Resource Type Extensions
This specification defined three new resource types. As is spelled
out in the VOResource specification, a resource description indicates
that it refers to one of these types of resources by setting the
xsi:type attribute to the namespace-qualified type name.
Doing so implies that the semantic meaning of that type applies to the
resource.
Standard
The vstd:Standard resource type describes any general
standard specification. This typically refers to an IVOA standard but
is not limited to such. Generally, the vstd:Standard
type is intended for standards other than standard
protocols (which should use the vstd:ServiceStandard type
instead). It extends the generic vr:Resource type as
follows.
<xs:complexType name="Standard" >
<xs:complexContent >
<xs:extension base="vr:Resource" >
<xs:sequence >
<xs:element name="endorsedVersion" type="vstd:EndorsedVersion"
maxOccurs="unbounded" />
<xs:element name="deprecated" type="xs:token" minOccurs="0" />
<xs:element name="key" type="vstd:StandardKey" minOccurs="0"
maxOccurs="unbounded" />
</sequence>
</extension>
</complexContent>
</complexType>
As one of the purposes of this resource type is to enable users to
discover the documentation that defines the standard that the resource
describes, the <referenceURL> should point either
to the stadard's specification document or to summary information about
the standard that can lead one to the specification document.
The vstd:Standard resource type adds two metadata terms
to the core set:
| vstd:Standard Extension Metadata Elements | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Element | Definition | ||||||||
| endorsedVersion |
| ||||||||
| deprecated |
| ||||||||
| key |
| ||||||||
The child <key> elements define terms with special
meaning to the standard; see section 3.2.
The purpose of the required <endorsedStandard>
element is to point potential users of the standard to the version
that is most preferred by the standard's publisher. If multiple
versions are relevant or in use, multiple elements may be given; in
this case, the use attribute can further help steer the
users to the preferred version.
<xs:complexType name="EndorsedVersion" >
<xs:simpleContent >
<xs:extension base="xs:string" >
<xs:attribute name="status" default="n/a" >
<xs:simpleType >
<xs:restriction base="xs:string" >
<xs:enumeration value="rec" />
<xs:enumeration value="prop" />
<xs:enumeration value="wd" />
<xs:enumeration value="n/a" />
</restriction>
</simpleType>
</attribute>
<xs:attribute name="use" >
<xs:simpleType >
<xs:restriction base="xs:string" >
<xs:enumeration value="preferred" />
<xs:enumeration value="deprecated" />
</restriction>
</simpleType>
</attribute>
</extension>
</simpleContent>
</complexType>
| vstd:EndorsedVersion Attributes | |||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Attribute | Definition | ||||||||||||||||||
| status |
| ||||||||||||||||||
| use |
| ||||||||||||||||||
When all versions of the standard are considered deprecated by the
resource publisher, the <deprecated> child element
should appear. The explanation given as a value should mention the
standard that the current standard is deprecated by when relevant.
- Note:
- An example where the
<deprecated>element might be used in the VO is in the case of the SkyNode standard [SkyNode]. As of this writing, there are many instances of SkyNode services available in the VO, and where they are used, version 1.01 is endorsed; however, the IVOA is deprecating this standard in favor of the Table Access Protocol.
<ri:Resource xsi:type="vstd:Standard" created="2001-12-31T12:00:00"
updated="2001-12-31T12:00:00" status="active">
<title>VOStandard: a VOResource Schema Extension for Describing IVOA Standards</title>
<identifier>ivo://ivoa.net/std/VOStandard</identifier>
<curation>
<publisher>IVOA</publisher>
<creator>
<name>IVOA</name>
<logo>http://www.ivoa.net/icons/ivoa_logo_small.jpg</logo>
</creator>
<date role="representative">2006-07-17</date>
<version>1.0</version>
<contact>
<name>IVOA Registry WG</name>
<email>registry@ivoa.net</email>
</contact>
</curation>
<content>
<subject>standard language identifiers</subject>
<subject>virtual observatory</subject>
<description>
This document describes an XML encoding standard for metadata about
IVOA standards themselves, referred to as VOStandard. We describe the
general model for the schema and explain how it may be included in
other schema as a methodology of avoiding XML enumerations. This
schema is primarily intended to support interoperable registries used
for discovering resources.
</description>
<referenceURL>http://www.ivoa.net/Documents/latest/VOStandard.html</referenceURL>
</content>
<endorsedVersion status="wd">1.0</endorsedVersion>
</ri:Resource>
ServiceStandard
The vstd:ServiceStandard resource type extends
vstd:Standard to describe more
specifically a standard protocol. It adds an
<interface> element to allow the interface defined
by the standard to be described in a machine-readable way. Its type
is defined to be vr:Interface, which is defined in the
VOResource schema [VR].
<xs:complexType name="ServiceStandard" >
<xs:complexContent >
<xs:extension base="vstd:Standard" >
<xs:sequence >
<xs:element name="interface" type="vr:Interface" minOccurs="0"
maxOccurs="unbounded" />
</sequence>
</extension>
</complexContent>
</complexType>
| vstd:ServiceStandard Extension Metadata Elements | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Element | Definition | ||||||||
| interface |
| ||||||||
Even though the vr:Interface type requires an
<accessURL> child element,
the <interface> element in a
vstd:ServiceStandard is intended to describe a service in
the abstract--i.e. without reference to a particular installation of the
service. Consequently, the accessURL should contain a bogus URL;
applications should not expect it to be resolvable.
An applications can, in principle, get a complete machine-readable
description of a particular instance of a standard service (to, say,
create a GUI for that service on-the-fly) by combining the general
description in the vstd:ServiceStandard record with the
service resource description for the specific instance. The intended
process for building that description is as follows:
- The application obtains a VOResource resource record for the service instance (e.g. from a registry).
- The application extracts the
standardIDattribute for the desired service capability. - The
standardIDis resolved (via a registry) to avstd:ServiceStandardrecord for the service. This description would capture the required and optional (but standard) components of the service interface. - The specific instance's interface description is merged into
the standard one. The service's support of optional components
as well as its allowed customizations would override the
generic description from the
vstd:ServiceStandardrecord.
- Note:
- A number of IVOA standard services (e.g. [SIA]) are registered using the
vs:ParamHTTPinterface type to describe its interface. This interface type allows one to list input parameters accepted by the service. Each parameter can be marked as required or optional. Avstd:ServiceStandardrecord for the SIA protocol can list the required and optional parameters defined by the SIA specification. A resource record for a real SIA service, then, need only list the optional parameters that it supports plus any custom parameters. Between the two records, an application can, in principle, build a GUI to the SIA service without knowing anything special about the SIA standard protocol.
StandardKeyEnumeration
The vstd:StandardKeyEnumeration resource type is available
for collecting definitions of related, standard keys. Each key defined
within this resource can then be referred to by a unique IVOA
Identifier URI (see section 3.2). To support
this, the vstd:StandardKeyEnumeration resource simply
adds the <keys> element to the standard core
metadata.
<xs:complexType name="StandardKeyEnumeration" >
<xs:complexContent >
<xs:extension base="vr:Resource" >
<xs:sequence >
<xs:element name="key" type="vstd:StandardKey" maxOccurs="unbounded"
minOccurs="1" />
</sequence>
</extension>
</complexContent>
</complexType>
| vstd:StandardKeyEnumeration Extension Metadata Elements | |||||||
|---|---|---|---|---|---|---|---|
| Element | Definition | ||||||
| key |
| ||||||
The contents of the <key> element is described in
the next section.
Defining Keys: StandardKey and StandardKeyURI
The vstd:StandardKey type provides the means to
define keys (as defined in section 2.3) within
a VOResource record.
<xs:complexType name="StandardKey" >
<xs:sequence >
<xs:element name="name" type="vstd:fragment" />
<xs:element name="description" type="xs:token" />
</sequence>
</complexType>
<xs:simpleType name="fragment" >
<xs:restriction base="xs:string" >
<xs:pattern value="([A-Za-z0-9;/\?:@&=\+$,\-_.!~\*'\(\)]|%[A-Fa-f0-9]{2})+" />
</restriction>
</simpleType>
| vstd:StandardKey Metadata Elements | |||||||
|---|---|---|---|---|---|---|---|
| Element | Definition | ||||||
| name |
| ||||||
| description |
| ||||||
Defining a key via a <key> element within a
VOResource record implies the definition of a unique URI formed
according to the syntax described in section
2.3 that represents the semantics given by the value of the
<description> child element. Because the URI must
be globally unique, the key name (given by the
<name> child element) must be unique within the
VOResource record.
Though it is not needed by VOStandard resource records, the VOStandard
schema further defines a convenience type,
vstd:StandardKeyURI, which defines the legal pattern for
a full standard key identifier (as defined in
section 2.3). Applications that wish to use
XML Schema to validate the form of a key URI may import the VOStandard
schema and use this type.
- Note:
- It is worth noting that just using or otherwise referencing a standard key URI in an application does not require importing the VOStandard nor need there be any reference to the VOStandard namespace. The role of the VOStandard schema is simply to provide a way of documenting the definitions in a VOResource record. Thus, an application may dereference the URI for display or user help purposes; however, dereferencing in not necessary to use the URI.
Appendix A: The complete VOStandard Schema
Note that this schema can be found on-line at http://www.ivoa.net/xml/VOStandard/v0.2 (i.e. the target namespace can also be used as a URL for the schema not yet uploaded for this draft) This location should represent the definitive source, the schema is only copied below for completeness of this document.
<?xml version="1.0" encoding="UTF-8"?> <xs:schema targetNamespace="http://www.ivoa.net/xml/VOStandard/v0.4" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:vr="http://www.ivoa.net/xml/VOResource/v1.0" xmlns:vstd="http://www.ivoa.net/xml/VOStandard/v0.4" xmlns:vm="http://www.ivoa.net/xml/VOMetadata/v0.1" elementFormDefault="unqualified" attributeFormDefault="unqualified" version="0.4rc0" > <xs:annotation> <xs:appinfo> <vm:schemaName>VOStandard</vm:schemaName> <vm:schemaPrefix>xs</vm:schemaPrefix> <vm:targetPrefix>vstd</vm:targetPrefix> </xs:appinfo> <xs:documentation> This is a core schema for describing IVOA Standards themselves </xs:documentation> </xs:annotation> <xs:import namespace="http://www.ivoa.net/xml/VOResource/v1.0" schemaLocation="http://www.ivoa.net/xml/VOResource/v1.0"/> <xs:complexType name="Standard"> <xs:annotation> <xs:documentation> a description of a standard specification. </xs:documentation> <xs:documentation> This typically refers to an IVOA standard but is not limited to such. </xs:documentation> </xs:annotation> <xs:complexContent> <xs:extension base="vr:Resource"> <xs:sequence> <xs:element name="endorsedVersion" type="vstd:EndorsedVersion" maxOccurs="unbounded"> <xs:annotation> <xs:documentation> the version of the standard that is recommended for use. </xs:documentation> <xs:documentation> More than one version can be listed, indicating that any of these versions are recognized as acceptable for use. </xs:documentation> </xs:annotation> </xs:element> <xs:element name="deprecated" type="xs:token" minOccurs="0"> <xs:annotation> <xs:documentation> when present, this element indicates that all versions of the standard are considered deprecated by the publisher. The value is a human-readable explanation for the designation. </xs:documentation> <xs:documentation> The explanation should indicate if another standard should be preferred. </xs:documentation> </xs:annotation> </xs:element> <xs:element name="key" type="vstd:StandardKey" minOccurs="0" maxOccurs="unbounded"> <xs:annotation> <xs:documentation> a defined key associated with this standard. </xs:documentation> </xs:annotation> </xs:element> </xs:sequence> </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="EndorsedVersion"> <xs:simpleContent> <xs:extension base="xs:string"> <xs:attribute name="status" default="n/a"> <xs:annotation> <xs:documentation> the IVOA status level of this verison of the standard. </xs:documentation> </xs:annotation> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="rec"> <xs:annotation> <xs:documentation> an IVOA Recommendation </xs:documentation> </xs:annotation> </xs:enumeration> <xs:enumeration value="prop"> <xs:annotation> <xs:documentation> an IVOA Proposed Recommendation </xs:documentation> </xs:annotation> </xs:enumeration> <xs:enumeration value="wd"> <xs:annotation> <xs:documentation> an IVOA Working Draft </xs:documentation> </xs:annotation> </xs:enumeration> <xs:enumeration value="n/a"> <xs:annotation> <xs:documentation> not an IVOA standard or protostandard at this time. </xs:documentation> </xs:annotation> </xs:enumeration> </xs:restriction> </xs:simpleType> </xs:attribute> <xs:attribute name="use"> <xs:annotation> <xs:documentation> A designation of preference for the version compared to other versions in use. </xs:documentation> </xs:annotation> <xs:simpleType> <xs:restriction base="xs:string"> <xs:enumeration value="preferred"> <xs:annotation> <xs:documentation> the most preferred version. </xs:documentation> <xs:documentation> Only one version should have this designation. </xs:documentation> </xs:annotation> </xs:enumeration> <xs:enumeration value="deprecated"> <xs:annotation> <xs:documentation> a versions whose use is now discouraged because a newer version is preferred. </xs:documentation> </xs:annotation> </xs:enumeration> </xs:restriction> </xs:simpleType> </xs:attribute> </xs:extension> </xs:simpleContent> </xs:complexType> <!-- I am not sure if this can really be used with the interface defined as below, as the that element has an accessURL, which can really only refer to a particular instance of a service Paul Harrison --> <!-- See the 4th comment to the interface element in the documentation below Ray Plante --> <xs:complexType name="ServiceStandard"> <xs:annotation> <xs:documentation> a description of a standard service protocol. </xs:documentation> <xs:documentation> This typically refers to an IVOA standard but is not limited to such. </xs:documentation> </xs:annotation> <xs:complexContent> <xs:extension base="vstd:Standard"> <xs:sequence> <xs:element name="interface" type="vr:Interface" minOccurs="0" maxOccurs="unbounded"> <xs:annotation> <xs:documentation> an abstract description of one of the interfaces defined by this service standard. </xs:documentation> <xs:documentation> This element can provide details about the interface that apply to all implementations. Each interface element should specify a role with a value starting with "std:" or, if there is only one standard interface, is equal to "std". </xs:documentation> <xs:documentation> Applications that, for example, wish to build a GUI to the service on-the-fly would first access this generic description. Site-specific variations, such as supported optional arguments or site specific arguments, would be given in the actual implemented service description and overrides any common information found in this generic description. This generic interface description can be matched with the site-specific one using the role attribute. </xs:documentation> <xs:documentation> Even though the Interface type requires an accessURL child element, this element is intended to describe a service in the abstract--i.e. without reference to a particular installation of the service. Consequently, the accessURL may contain a bogus URL; applications should not expect it to be resolvable. </xs:documentation> </xs:annotation> </xs:element> </xs:sequence> </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="StandardKeyEnumeration"> <xs:annotation> <xs:documentation> A registered set of related keys. Each key can be uniquely identified by combining the IVOA identifier of this resource with the key name separated by the URI fragment delimiter, #, as in: ivoa-identifiery#key-name </xs:documentation> </xs:annotation> <xs:complexContent> <xs:extension base="vr:Resource"> <xs:sequence> <xs:element name="key" type="vstd:StandardKey" maxOccurs="unbounded" minOccurs="1"> <xs:annotation> <xs:documentation> the name and definition of a key--a named concept, feature, or property. </xs:documentation> </xs:annotation> </xs:element> </xs:sequence> </xs:extension> </xs:complexContent> </xs:complexType> <xs:complexType name="StandardKey"> <xs:annotation> <xs:documentation> The name and definition of a key--a named concept, feature, or property. </xs:documentation> <xs:documentation> This key can be identified via an IVOA identifier of the form ivo://authority/resource#name where name is the value of the child name element. </xs:documentation> <xs:documentation> This type can be extended if the key has other metadata associated with it. </xs:documentation> </xs:annotation> <xs:sequence> <xs:element name="name" type="vstd:fragment"> <xs:annotation> <xs:documentation> The property identifier which would appear as the fragment (string after the pound sign, #) in an IVOA identifier. </xs:documentation> </xs:annotation> </xs:element> <xs:element name="description" type="xs:token"> <xs:annotation> <xs:documentation> A human-readable definition of this property. </xs:documentation> </xs:annotation> </xs:element> </xs:sequence> </xs:complexType> <xs:simpleType name="StandardKeyURI"> <xs:annotation> <xs:documentation> reference that forces an IVOA ID with a # fragment part appended to match the standard pattern for registering enumeration values with a vstd:StandardKeyList </xs:documentation> </xs:annotation> <xs:restriction base="xs:anyURI"> <xs:pattern value="ivo://[\w\d][\w\d\-_\.!~\*'\(\)\+=]{2,}(/[\w\d\-_\.!~\*'\(\)\+=]+(/[\w\d\-_\.!~\*'\(\)\+=]+)*)?(#([A-Za-z0-9;/\?:@&=\+$,\-_\.!~\*'\(\)]|%[A-Fa-f0-9]{2})+)?"/> </xs:restriction> </xs:simpleType> <xs:simpleType name="fragment"> <xs:annotation> <xs:documentation> the allowed characters for a fragment identifier taken from rfc2396 </xs:documentation> </xs:annotation> <xs:restriction base="xs:string"> <xs:pattern value="([A-Za-z0-9;/\?:@&=\+$,\-_\.!~\*'\(\)]|%[A-Fa-f0-9]{2})+"/> </xs:restriction> </xs:simpleType> </xs:schema>
Appendix B: Change History
Changes since WD-v0.4:
- removed App. B. (Sample instance) as examples appear throughout the document.
References
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Last modified: Fri May 14 10:09:49 2010