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Split collection example
Do a basic collection/item example, and then add pagination as yet another example.
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‎jsonschema-hyperschema.xml‎

Lines changed: 186 additions & 112 deletions
Original file line numberDiff line numberDiff line change
@@ -1913,10 +1913,9 @@ Link: <https://api.example.com/trees/1/nodes/456> rev=up
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<figure>
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<preamble>
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This schema describes a collection where each item representation is
1916-
identical to the individual resource item representation, and there
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is enough metadata included in the collection representation to
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produce pagination links. The "first" and "last" pagination links
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were omitted as this is already a long example.
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identical to the individual resource item representation. The actual
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collection elements appear as an array within an object, as we will
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add more fields to the object in the next example.
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</preamble>
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<artwork>
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<![CDATA[{
@@ -1940,13 +1939,173 @@ Link: <https://api.example.com/trees/1/nodes/456> rev=up
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}
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]
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}
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}
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},
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"links": [
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{
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"rel": "self",
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"href": "things",
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"targetSchema": {"$ref": "#"}
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}
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]
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}]]>
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</artwork>
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</figure>
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<figure>
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<artwork>
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<![CDATA[{
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"elements": [
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{"id": 12345, "data": {}},
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{"id": 67890, "data": {}}
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]
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}]]>
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</artwork>
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</figure>
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<figure>
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<preamble>
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Here are all of the links that apply to this instance,
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including those that are referenced by using the "thing"
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schema for the individual items. The "self" links for
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the overall resource and each individual item are
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distinguished by different context pointers. Note also
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that the "item" and "self" links for a given thing have
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identical target URIs but different context pointers.
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</preamble>
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<artwork>
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<![CDATA[[
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{
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"contextUri": "https://api.example.com/things",
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"contextPointer": "",
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"rel": "self",
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"targetUri": "https://api.example.com/things",
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"attachmentPointer": ""
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},
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{
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"contextUri": "https://api.example.com/things",
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"contextPointer": "",
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"rel": "item",
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"targetUri": "https://api.example.com/things/1234",
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"attachmentPointer": "/elements/0"
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},
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{
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"contextUri": "https://api.example.com/things",
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"contextPointer": "",
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"rel": "item",
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"targetUri": "https://api.example.com/things/67890",
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"attachmentPointer": "/elements/1"
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},
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{
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"contextUri": "https://api.example.com/things",
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"contextPointer": "/elements/0",
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"rel": "self",
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"targetUri": "https://api.example.com/things/1234",
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"attachmentPointer": "/elements/0"
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},
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{
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"contextUri": "https://api.example.com/things",
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"contextPointer": "/elements/1",
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"rel": "self",
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"targetUri": "https://api.example.com/things/67890",
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"attachmentPointer": "/elements/1"
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}
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]]]>
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</artwork>
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</figure>
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<t>
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To fully specify our collection, we also need to add the following
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link to our "thing" schema. Note that this would cause it to also
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appear as a link in each item in the collection representation, which
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is a good example of why it is best to only construct links upon request.
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There is no need for having as many functionally identical "collection"
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links as there are items in a collection page on every collection
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representation.
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</t>
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<figure>
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<preamble>
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This link would be added to the top-level "links" array in the
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"https://schemasexample.com/thing" schema.
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</preamble>
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<artwork>
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<![CDATA[{
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"rel": "collection",
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"href": "/things",
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"targetSchema": {"$ref": "thing-collection#"},
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"submissionSchema": {"$ref": "#"}
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}]]>
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</artwork>
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<postamble>
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Here we see the "submissionSchema" indicating that we can create
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a single "thing" by submitting a representation (minus server-created
2040+
fields such as "id") to the collection that is this link's target
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schema. While we cannot, in general, make assumptions about the
2042+
semantics of making a data submission request (in HTTP terms, a POST),
2043+
<xref target="collectionAndItem" /> tells us that we MAY make such
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an assumption when the link relation is "collection", and that
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hyper-schema authors MUST NOT use a "collection" link if the data
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submission operation has semantics other than item creation.
2047+
</postamble>
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</figure>
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<t>
2050+
But what if we do not have any "thing"s yet? We cannot get to the
2051+
individual "thing" schema as there is no individual "thing" to fetch.
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And the "tag:rel.example.com,2017:thing" link in the entry point
2053+
resource does not indicate how to create a "thing". The "self" link
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requires the "id" to already exist, but it is assigned by the server.
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So we need to add another link to our entry point schema:
2056+
</t>
2057+
<figure>
2058+
<preamble>
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This LDO would be added to the top-level "links" array in the entry
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point resource's hyper-schema.
2061+
</preamble>
2062+
<artwork>
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<![CDATA[{
2064+
"rel": "tag:rel.example.com,2017:thing-collection",
2065+
"href": "/things",
2066+
"submissionSchema": {
2067+
"$ref": "thing#"
2068+
},
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"targetSchema": {
2070+
"$ref": "thing-collection#"
2071+
}
2072+
}]]>
2073+
</artwork>
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</figure>
2075+
<t>
2076+
<cref>
2077+
Here we also see the "submissionSchema" to use to create a "thing",
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but how do we recognize it? We can't use a "collection" link relation
2079+
here, because there is no identifiable "thing" to serve as the context
2080+
resource. We could look at the submission schema, notice that it
2081+
has a "collection" link and is therefore an item, and notice that
2082+
its "collection" link produces the same(-ish?) URI, but that seems
2083+
overly complicated. And gets more so once pagination and filtering
2084+
are introduced.
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</cref>
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</t>
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</section>
2088+
<section title="Pagination">
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<figure>
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<preamble>
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Here we add pagination to our collection. There is a "meta" section
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to hold the information about current, next, and previous pages.
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Most of the schema is the same as in the previous section and has been
2094+
omitted. Only new fields and new or (in the case of the main "self" link)
2095+
changed links are shown in full.
2096+
</preamble>
2097+
<artwork>
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<![CDATA[{
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"properties": {
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"elements": {
2101+
...
19432102
},
19442103
"meta": {
19452104
"type": "object",
19462105
"properties": {
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"prev": {"$ref": "#/definitions/scrolling"},
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"current": {"$ref": "#/definitions/scrolling"},
1949-
"next": {"$ref": "#/definitions/scrolling"}
2106+
"prev": {"$ref": "#/definitions/pagination"},
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"current": {"$ref": "#/definitions/pagination"},
2108+
"next": {"$ref": "#/definitions/pagination"}
19502109
}
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}
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},
@@ -1983,7 +2142,7 @@ Link: <https://api.example.com/trees/1/nodes/456> rev=up
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}
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],
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"definitions": {
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"scrolling": {
2145+
"pagination": {
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"type": "object",
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"properties": {
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"offset": {
@@ -2006,12 +2165,13 @@ Link: <https://api.example.com/trees/1/nodes/456> rev=up
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Notice that the "self" link includes the pagination query
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that produced the exact representation, rather than being
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a generic link to the collection allowing selecting the
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page via input. There is no link for manual page selection
2010-
in the example as shown here, nor is there a "submissionSchema"
2011-
for item creation, but we will consider those additions further down.
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page via input.
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</postamble>
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</figure>
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<figure>
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<preamble>
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Given this instance:
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</preamble>
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<artwork>
20162176
<![CDATA[{
20172177
"elements": [
@@ -2033,13 +2193,9 @@ Link: <https://api.example.com/trees/1/nodes/456> rev=up
20332193
</figure>
20342194
<figure>
20352195
<preamble>
2036-
Here are all of the links that apply to this instance,
2037-
including those that are referenced by using the "thing"
2038-
schema for the individual items. The "self" links for
2039-
the overall resource and each individual item are
2040-
distinguished by different context pointers. Note also
2041-
that the "item" and "self" links for a given thing have
2042-
identical target URIs but different context pointers.
2196+
Here are all of the links that apply to this instance
2197+
that either did not appear in the previous example or
2198+
have been changed with pagination added.
20432199
</preamble>
20442200
<artwork>
20452201
<![CDATA[[
@@ -2058,34 +2214,6 @@ Link: <https://api.example.com/trees/1/nodes/456> rev=up
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"targetUri":
20592215
"https://api.example.com/things?offset=22,limit=2",
20602216
"attachmentPointer": ""
2061-
},
2062-
{
2063-
"contextUri": "https://api.example.com/things",
2064-
"contextPointer": "",
2065-
"rel": "item",
2066-
"targetUri": "https://api.example.com/things/1234",
2067-
"attachmentPointer": "/elements/0"
2068-
},
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{
2070-
"contextUri": "https://api.example.com/things",
2071-
"contextPointer": "",
2072-
"rel": "item",
2073-
"targetUri": "https://api.example.com/things/67890",
2074-
"attachmentPointer": "/elements/1"
2075-
},
2076-
{
2077-
"contextUri": "https://api.example.com/things",
2078-
"contextPointer": "/elements/0",
2079-
"rel": "self",
2080-
"targetUri": "https://api.example.com/things/1234",
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"attachmentPointer": "/elements/0"
2082-
},
2083-
{
2084-
"contextUri": "https://api.example.com/things",
2085-
"contextPointer": "/elements/1",
2086-
"rel": "self",
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"targetUri": "https://api.example.com/things/67890",
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"attachmentPointer": "/elements/1"
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}
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]]]>
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@@ -2097,49 +2225,15 @@ Link: <https://api.example.com/trees/1/nodes/456> rev=up
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that the link is not usable with this particular instance.
20982226
</postamble>
20992227
</figure>
2100-
<t>
2101-
To fully specify our collection, we also need to add the following
2102-
link to our "thing" schema. Note that this would cause it to also
2103-
appear as a link in each item in the collection representation, which
2104-
is a good example of why it is best to only construct links upon request.
2105-
There is no need for having as many functionally identical "collection"
2106-
links as there are items in a collection page on every collection
2107-
representation.
2108-
</t>
2109-
<figure>
2110-
<preamble>
2111-
This link would be added to the top-level "links" array in the
2112-
"https://schema.example.com/thing" schema.
2113-
</preamble>
2114-
<artwork>
2115-
<![CDATA[{
2116-
"rel": "collection",
2117-
"href": "/things",
2118-
"targetSchema": {"$ref": "thing-collection#"},
2119-
"submissionSchema": {"$ref": "#"}
2120-
}]]>
2121-
</artwork>
2122-
<postamble>
2123-
Here we see the "submissionSchema" indicating that we can create
2124-
a single "thing" by submitting a representation (minus server-created
2125-
fields such as "id") to the collection that is this link's target
2126-
schema. While we cannot, in general, make assumptions about the
2127-
semantics of making a data submission request (in HTTP terms, a POST),
2128-
<xref target="collectionAndItem" /> tells us that we MAY make such
2129-
an assumption when the link relation is "collection", and that
2130-
hyper-schema authors MUST NOT use a "collection" link if the data
2131-
submission operation has semantics other than item creation.
2132-
</postamble>
2133-
</figure>
21342228
<t>
21352229
<cref>
2136-
I left off the scrolling parameters for this link. Technically,
2137-
the link should go to the page containing the specific "thing"
2138-
that is the context of the link. If the collection is using
2139-
semantic sorting, then this is do-able (ideally setting
2140-
the page boundary such that this is the first item, and allowing
2141-
input on the page count / "limit" parameter). But getting into
2142-
semantic scrolling/pagination seems way too involved for this
2230+
It's not clear how pagination should work with the link from the
2231+
entry point resource or the "collection" link in the item.
2232+
Technically, link from an item to a paginated or filtered
2233+
collection should go to a page/filter that contains the link
2234+
context. If the collection is using semantic sorting instead
2235+
of a plain integer limit and offset, then this is possible.
2236+
But getting into semantic pagination seems way too involved for this
21432237
example.
21442238
</cref>
21452239
</t>
@@ -2154,24 +2248,16 @@ Link: <https://api.example.com/trees/1/nodes/456> rev=up
21542248
</cref>
21552249
</t>
21562250
<t>
2157-
But what if we do not have any "thing"s yet? We cannot get to the
2158-
individual "thing" schema as there is no individual "thing" to fetch.
2159-
And the "tag:rel.example.com,2017:thing" link in the entry point
2160-
resource does not indicate how to create a "thing". The "self" link
2161-
requires the "id" to already exist, but it is assigned by the server.
2162-
So we need to add another link to our entry point schema:
2251+
Let's also update our entry point link to include pagination, specifically
2252+
allowing arbitrary input to choose the page:
21632253
</t>
21642254
<figure>
2165-
<preamble>
2166-
This LDO would be added to the top-level "links" array in the entry
2167-
point resource's hyper-schema.
2168-
</preamble>
21692255
<artwork>
21702256
<![CDATA[{
21712257
"rel": "tag:rel.example.com,2017:thing-collection",
21722258
"href": "/things{?offset,limit}",
21732259
"hrefSchema": {
2174-
"$ref": "thing-collection#/definitions/scrolling"
2260+
"$ref": "thing-collection#/definitions/pagination"
21752261
},
21762262
"submissionSchema": {
21772263
"$ref": "thing#"
@@ -2182,22 +2268,10 @@ Link: <https://api.example.com/trees/1/nodes/456> rev=up
21822268
}]]>
21832269
</artwork>
21842270
<postamble>
2185-
Now we see the scrolling parameters being accepted as input, so
2186-
we can jump to any scroll window within the collection.
2271+
Now we see the pagination parameters being accepted as input, so
2272+
we can jump to any page within the collection.
21872273
</postamble>
21882274
</figure>
2189-
<t>
2190-
<cref>
2191-
Here we also see the "submissionSchema" to use to create a "thing",
2192-
but how do we recognize it? We can't use a "collection" link relation
2193-
here, because there is no identifiable "thing" to serve as the context
2194-
resource. We could look at the submission schema, notice that it
2195-
has a "collection" link and is therefore an item, and notice that
2196-
its "collection" link produces the same(-ish?) URI, but that seems
2197-
overly complicated and also gets into trouble with query parameters
2198-
again.
2199-
</cref>
2200-
</t>
22012275
</section>
22022276
</section>
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