## Implementation Considerations
### Content Type and Encodings

The formal MIME-type for FHIR resources is application/fhir+json or application/fhir+xml. The correct mime type SHALL be used by clients and servers:

•	JSON(preferred): application/fhir+json

•	XML: application/fhir+xml

FHIR uses UTF-8 for all request and response bodies. Since the HTTP specification defines a default character encoding of ISO-8859-1, requests and responses SHALL explicitly set the character encoding to UTF-8 using the charset parameter of the MIME-type in the Content-Type header. Requests MAY also specify this charset parameter in the Accept header and/or use the Accept-Charset header.

Accept-Language field in HTTP header to set the language of the search will be considered for future releases. The current default language for search is English only.

### MustSupport
To maximize interoperability, this implementation guide uses MustSupport flag to identify elements that implementers must understand in order to properly interpret the data in the response. As requird by FHIR standard, MustSupport may have different meaning depending on the use case and each implementation must provide the exact meaning of this flag. Please refer to the guidance below:

- If an element is marked with "MustSupport" flag, acCDR supports the element in accordance with the definition in the profile. The consuming application of acCDR FHIR interface SHALL handle the element in a meaninful way.

- If element is not marked with "MustSupport" flag, in acCDR FHIR response, it will not be populated. If the element is used in acCDR FHIR request or data submission, acCDR will ignore the element and will not generate an error.

### Summary Flag and summary searches
Some elements are identified with summary flags. Summary searches are supported in this implementation guide. To use summary search, the query must contain "_summary=true". The server will return only fields with summary flags.

### Paging
To preserve network bandwidth and improve performance, the acCDR FHIR interface supports paging for document search response. If the number of resources in the response exceeds a pre-defined limit, the bundle will contain `link` elements to help client traverse the pages. The `link` element contains `relation` and `url` child elements. The `relation` element specifies the pointer to other pages, which is specified in the corresponding `url` element.

~~~~
<link>
    <relation value="self">
    <url value="http://example.org/DocumentReference[?search-expression]&page=3"/>
  </link>
  <!-- link to the first page -->
  <link>
    <relation value="first"/>
    <url value="http://example.org/Patient?name=peter&stateid=23&page=1"/>
  </link>
  <!-- link to the previous page -->
  <link>
    <relation value="previous"/>
    <url value="http://example.org/Patient?name=peter&stateid=23&page=2"/>
  </link>
  <!-- link to the next page -->
  <link>
    <relation value="next"/>
    <url value="http://example.org/Patient?name=peter&stateid=23&page=4"/>
  </link>
  <!-- link to the last page -->
  <link>
    <relation value="last"/>
    <url value="http://example.org/Patient?name=peter&stateid=23&page=26"/>
  </link>`