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<p>This design document covers a superset of the clojure.xml schema.</p><p>All metadata are optional, parsers SHOULD provide them and serializers MAY leverage it: metadata is not required to be kept in sync with their data so it's up to the serializers heuristics to use or ignore them.</p><h1>Namespaces</h1><p>A namespace aware XML parser produces a datastructure following these representations, this representation is designed as a superset of the clojure.xml representation:</p><table class="confluenceTable"><tbody><tr><th class="confluenceTh">XML</th><th colspan="1" class="confluenceTh">Clojure</th><th class="confluenceTh">Notes</th></tr><tr><td class="confluenceTd">Element</td><td colspan="1" class="confluenceTd"><pre>^{::xml/ns {&quot;&quot; &quot;http://...&quot;<br />            &quot;x&quot; &quot;http://...&quot;}<br />  ::xml/prefix &quot;x&quot;}<br />{:tag :foo<br /> :uri &quot;http://...&quot;<br /> :attrs {...}<br /> :content [...]}</pre></td><td class="confluenceTd"><p>A map with keys: :tag (local name keywordized), :attrs (attribute map), :content (nil, sequence, sequential collection of nodes), :uri (namespace URI as string).</p><p>Metadata: under the ::xml/ns key, a map of prefixes (strings) to URIs (strings), under the ::xml/prefix a string of the original prefix.</p><p>(where xml is an alias for data.xml)</p></td></tr><tr><td class="confluenceTd">Attribute</td><td colspan="1" class="confluenceTd"><pre>^{::xml/ns {&quot;&quot; &quot;http://...&quot;<br />            &quot;x&quot; &quot;http://...&quot;}<br />  ::xml/prefix &quot;x&quot;}<br />[:href &quot;http://...&quot;]</pre></td><td class="confluenceTd"><p>A map entry whose key is either a keyword (no prefix) or a [:kw &quot;uri&quot;] pair; the value is a string.</p><p>In the case of [:kw &quot;uri&quot;] keys, ::xml/prefix SHOULD be present</p><p>the uri MUST NOT be nil or the empty string</p></td></tr><tr><td class="confluenceTd">Text nodes</td><td colspan="1" class="confluenceTd"><pre> &quot;text&quot;</pre></td><td class="confluenceTd"> </td></tr><tr><td colspan="1" class="confluenceTd">Comment</td><td colspan="1" class="confluenceTd"><pre> {:comment &quot;text&quot;}</pre></td><td colspan="1" class="confluenceTd"> </td></tr><tr><td colspan="1" class="confluenceTd">...</td><td colspan="1" class="confluenceTd"> </td><td colspan="1" class="confluenceTd">TBD</td></tr></tbody></table><h1>Default serialization strategy suggestion</h1><p>The default serialization strategy is conservative.</p><p>When serializing an element: add missing namespaces declarations.</p><p>For each name (elements or attributes name):</p><ol><li>If the ::xml/prefix matches the :uri then use it,</li><li>if the uri is mapped to another alias, use it, (Should we rather map the url to the new alias?)</li><li>if the uri is not mapped then map it under the specified alias (if present) or a gensymed alias.</li></ol><p>For elements:</p><p>emit xmlns and xmlns:* attributes for new mappings (generated by attributes serialization and by new entries under the ::xml/ns key – new when compared to the state maintained by the serializer).</p><p> </p><h1>Custom serialization strategies</h1><p>To please broken consumers, XML serialization has to be tweaked. It may be interesting to have emit or *xml-emitter* or somethieng to be a dynamic var.</p><p> </p><p>Less than half-baked idea:</p><p>Defining a full serializer is tiresome so it may be interesting to provide a factory.</p><table class="wysiwyg-macro" data-macro-name="code" data-macro-parameters="title=serializer" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGU6dGl0bGU9c2VyaWFsaXplcn0&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>(serializer 
  init ; internal state of the serializer, initial value 
  (fn [state xmlns] state') ; fn to update internal state given a new xmlns map
  (fn [state local-name uri prefix] prefix')) ; fn which decides which prefix to use for a given name</pre></td></tr></table><p>All serialization quirks can't be solved by emitters produced by such a factory but if it covers a good chunk it may be worthy.</p><p>There must be a better abstraction.</p>