Target-complete
URIIdentifier[s1]
A target-complete URI Identifier is
a URI or IRI that contains all the information required to locate a target of
an SML reference. It is a consequence of
this definition that a target-complete
identifier cannot be a relative
reference.[s2]
To determine if two targets are the same or different, a model validator MUST obey the following rules.
1.
If both of the following are true, then a[s3]A
model validator MUST consider both targets to be the
same when both of the following are true.
1.
The definition of the scheme(s) used to locate the targets specifies
that the scheme uses target-complete URIstarget-complete identifiers. [4.3
Reference Schemes]
2.
The two URIs or IRIstarget-complete identifiers
used to locate the targets are identical using a case-sensitive, codepoint-by-codepoint
comparison.
2.
Otherwise aA model
validator MUST consider both targets to be different
when there is something available in the element information items for the
targets that tells them apart. For example, if there is an infoset property for
which the 2 targets have different values, they are different. This applies
recursively for complex-valued properties.
3. For all other cases, it is implementation-defined whether to treat the targets as the same or not.
An SML reference MAY be represented by using a variety of schemes, including those defined in this specification. SML does not mandate the use of any specific schemes. A reference scheme MAY use child elements, attributes, both, or neither to capture the information necessary to identify the reference target. It is not required that all elements in an SML model be reachable via an SML reference. This will depend on the support defined by the chosen reference scheme.
Although SML does not require the use of any specific scheme, it does specify how a reference MUST be represented when using SML-defined reference schemes. This specification defines the 4.3.1 SML URI Scheme for identifying reference targets.
All of the following MUST be defined for each SML reference scheme,
1.
The set of rules that, when satisfied, identify a reference element as containing
one and the only an instance of the scheme within
that reference element.
2.
The set of rules that, when evaluated, resolve the containing reference
to a set of target element nodes.[s4]
3.
An assertion that states whether or not the scheme uses target-complete URIstarget-complete identifiers. Using target-complete identifiers
requires all the following:
1. URI-references or IRI-references are specified in instances of the scheme. These references may or may not be target-complete identifiers.
2. If these references are allowed to be relative references, i.e. they are not already target-complete, then some implementation-dependent base URI/IRI is used to resolve them to URIs or IRIs. [See section 5 of RFC 3986 and section 6.5 of RFC 3987.]
3. The resulting references are target-complete identifiers.[s5]
A schema scheme definition
MAY impose additional requirements on references
recognized as instances of that scheme. Such requirements, if any, MUST NOT be applied by scheme implementations to
references that are not instances of the corresponding scheme.
The SML URI Scheme is defined as follows:
1.
An SML reference element is identified as using the SML URI scheme if
and only if exactly one element information item whose [local name] is
uri and whose [namespace name]
is http://www.w3.org/2008/01/sml
is present as a child of that reference element.
2. The SML URI scheme is resolved using the following steps:
1. If the URI is a relative reference, then use an implementation dependent base URI to resolve it to an URI.
1.2.A
document is obtained by dereferencing the URI reference, sans ignoring
its fragment identifiercomponent,
using the appropriate operation defined for the scheme used in that URI
reference. If there is no document retrieved, the scheme instance is
unresolved.
2.3.If
a
no fragment identifier component
is not present in the URI reference, the
scheme instance resolves to the root element of the retrieved document.
3.4.If
a fragment identifier component is
present in the URI reference, the scheme instance resolves to the set of
elements obtained by applying the fragment identifier component
to the root element of the retrieved document.
3.
The SML URI Scheme's uri
element contains a uses target-complete URItarget-complete identifiers.
4. Scheme syntax:
SMLURI ::=
URI ('#' SMLXPath1_Fragment_ID)?
where ,
1.
URI is a URI
reference without a fragment identifiercomponent.
2.
SMLXPath1_Fragment_ID
is a production that defines the syntax of the fragment portion of the SML URI
scheme. This is defined in section 4.3.1.1
The smlxpath1() scheme.
When processing an SML-IF document, there are 3 categories of URI references that may need to be resolved:
1.
schemaLocation
attributes on xs:include and
xs:redefine in schema
documents, when they are model definition documents.
2.
URI references specified in instances of SML
reference schemes that use Targettarget-complete
URIs [SML
1.1] used in SML reference schemes. For a URI reference
to be in this category, its non-fragment URI components have all the
information to uniquely identify at most one model document that potentially
contains the target(s) of the URI reference. [s6]
3.
URI references used specified in
instances
of SML reference schemes which are not in category
#2that do not use target-complete URIs.
[s1]Changing ¡°URI¡± to ¡°identifier¡±, because this term is used to cover both URI and IRI.
[s2]Target-complete identifiers are the ones actually used to locate targets, also the ones used to compare for target identity. Relative references (typically) can¡¯t be used for either purpose.
[s3]This change is to specify the order in which conditions in bullet 1 and 2 are checked, to avoid the question ¡°what if both 1 and 2 are true¡±.
[s4]The above 3 changes are made to reflect the decision we made earlier: ¡°SML references *are* scheme instances¡±, as opposed to ¡°SML references *contain* schema instances¡±.
[s5]We want to require that these schemes must start with a URI/IRI, and absolutize it if necessary. Otherwise a scheme can claim to be ¡°using target-complete identifiers¡± even when it doesn¡¯t use URI/IRI at all, because it can say ¡°I have an imagined/computed identifier that¡¯s target complete¡±.
[s6]The old bullet 2 was already covered by the definition for target-complete identifiers.