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Revert changes to dynamic scope regarding dependence on instance #1053

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Dec 7, 2020
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Revert changes to dynamic scope regarding dependence on instance #1053

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50 changes: 28 additions & 22 deletions jsonschema-core.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -654,11 +654,13 @@
appear in a schema resource's root schema.
</t>
<t>
Other keywords may take into account the dynamic scope that exists during the
evaluation of a schema. The outermost dynamic scope is the root schema of the
schema document in which processing begins. The path from this root schema to
any particular keyword (that includes any "$ref" and "$dynamicRef" keywords that
may have been resolved) is considered the keyword's "validation path."
Other keywords may take into account the dynamic scope that
exists during the evaluation of a schema, typically together
with an instance document. The outermost dynamic scope is the
root schema of the schema document in which processing begins.
The path from this root schema to any particular keyword (that
includes any "$ref" and "$dynamicRef" keywords that may have
been resolved) is considered the keyword's "validation path."
</t>
<t>
Lexical and dynamic scopes align until a reference keyword
Expand Down Expand Up @@ -733,7 +735,7 @@
<t>
Canonical schema URIs MUST NOT change while processing an instance, but
keywords that affect URI-reference resolution MAY have behavior that
is only fully determined dynamically.
is only fully determined at runtime.
</t>
<t>
While custom identifier keywords are possible, vocabulary designers should
Expand Down Expand Up @@ -790,10 +792,12 @@
of an instance against a schema.
</t>
<t>
For some by-reference applicators, such as <xref target="ref">"$ref"</xref>, the
referenced schema can be determined by static analysis of the schema document's
lexical scope. Others, such as "$dynamicRef" (with "$dynamicAnchor"), are only
resolvable with knowledge of all the schemas in it's dynamic scope.
For some by-reference applicators, such as
<xref target="ref">"$ref"</xref>, the referenced schema can be determined
by static analysis of the schema document's lexical scope. Others,
such as "$dynamicRef" (with "$dynamicAnchor"), may make use of dynamic
scoping, and therefore only be resolvable in the process of evaluating
the schema with an instance.
</t>
</section>
</section>
Expand Down Expand Up @@ -1462,28 +1466,30 @@
<t>
The value of the "$ref" keyword MUST be a string which is a URI-Reference.
Resolved against the current URI base, it produces the URI of the schema
to apply. This resolution is safe to perform on schema load as neither other
schemas nor the instance can change how the reference resolves.
to apply. This resolution is safe to perform on schema load, as the
process of evaluating an instance cannot change how the reference resolves.
</t>
</section>

<section title='Dynamic References with "$dynamicRef"' anchor="dynamic-ref">
<t>
The "$dynamicRef" keyword is an applicator that is used to reference a
dynamically identified schema.
The "$dynamicRef" keyword is an applicator that allows for deferring the
full resolution until runtime, at which point it is resolved each time it is
encountered while evaluating an instance.
</t>
<t>
Together with "$dynamicAnchor", "$dynamicRef" implements a cooperative
extension mechanism that is primarily useful with recursive schemas
(schemas that reference themselves). Both the extension point and the
extension target are defined with "$dynamicAnchor", and only exhibit dynamic
behavior when referenced with "$dynamicRef".
runtime-determined extension target are defined with "$dynamicAnchor",
and only exhibit runtime dynamic behavior when referenced with
"$dynamicRef".
</t>
<t>
The value of the "$dynamicRef" property MUST be a string which is a
URI-Reference. Resolved against the current URI base, it produces the URI used
as the starting point for resolution. This initial resolution is safe to perform
on schema load.
The value of the "$dynamicRef" property MUST be a string which is
a URI-Reference. Resolved against the current URI base, it produces
the URI used as the starting point for runtime resolution. This initial
resolution is safe to perform on schema load.
</t>
<t>
If the initially resolved starting point URI includes a fragment that
Expand All @@ -1493,8 +1499,8 @@
an identically named fragment with "$dynamicAnchor".
</t>
<t>
Otherwise, its behavior is identical to "$ref", and no dynamic resolution is
needed.
Otherwise, its behavior is identical to "$ref", and no runtime
resolution is needed.
</t>
<t>
For a full example using these keyword, see appendix
Expand Down