Formal Definition for _filter parameter (id = "filter")

<?xml version="1.0" encoding="UTF-8"?>

<SearchParameter xmlns="http://hl7.org/fhir">
  <id value="filter"/> 
  <text> <status value="generated"/> <div xmlns="http://www.w3.org/1999/xhtml"><p> <b> Generated Narrative: SearchParameter</b> <a name="filter"> </a> </p> <div style="display: inline-block; background-color: #d9e0e7; padding: 6px; margin: 4px; border:
       1px solid #8da1b4; border-radius: 5px; line-height: 60%"><p style="margin-bottom: 0px">Resource SearchParameter &quot;filter&quot; </p> </div> <p> <b> url</b> : <code> http://hl7.org/fhir/SearchParameter/filter</code> </p> <p> <b> version</b> : 1</p> <p> <b> name</b> : FilterSearchParameter</p> <p> <b> title</b> : Filter Search Parameter</p> <p> <b> status</b> : draft</p> <p> <b> experimental</b> : false</p> <p> <b> date</b> : 2018-07-26</p> <p> <b> publisher</b> : Health Level Seven International (FHIR Infrastructure)</p> <p> <b> contact</b> : FHIR Project: <a href="http://hl7.org/fhir">http://hl7.org/fhir</a> </p> <p> <b> description</b> : This is the formal declaration for the _filter parameter, documented at [http://hl7.org/fhi
        r/search_filter.html](http://hl7.org/fhir/search_filter.html)</p> <p> <b> purpose</b> : Support combination searches when the simple name=value basis of search cannot
         express what is required</p> <p> <b> code</b> : _filter</p> <p> <b> base</b> : Resource</p> <p> <b> type</b> : special</p> </div> </text> <url value="http://hl7.org/fhir/SearchParameter/filter"/> 
  <version value="1"/> 
  <name value="FilterSearchParameter"/> 
  <title value="Filter Search Parameter"/> 
  <status value="draft"/> 
  <experimental value="false"/> 
  <date value="2018-07-26"/> 
  <publisher value="Health Level Seven International (FHIR Infrastructure)"/> 
  <contact> 
    <name value="FHIR Project"/> 
    <telecom> 
      <system value="url"/> 
      <value value="http://hl7.org/fhir"/> 
    </telecom> 
  </contact> 
  <description value="This is the formal declaration for the _filter parameter, documented at [http://hl7.org/fhir/
  search_filter.html](http://hl7.org/fhir/search_filter.html)"/> 
  <purpose value="Support combination searches when the simple name=value basis of search cannot
   express what is required"/> 
  <code value="_filter"/> 
  <base value="Resource"/> 
  <type value="special"/> 
</SearchParameter>