Padding in DICOM JSON Model Status November 2019 Voting Packet Date of Last Update 2019/10/27 Person Assigned David Clunie Submitter Name Jim Philbin Submission Date 2018/11/08 Correction Number CP-1920 Log Summary: Padding in DICOM JSON and XML (Native) Models Name of Standard PS3.18, PS3.19 Rationale for Correction: JSON does not pad value fields. Clarify this and make consistent with XML rules from PS3.19. Correction Wording: JSON is a text-based open standard, derived from JavaScript, for representing data structures and associated arrays. It is language-independent, and primarily used for serializing and transmitting lightweight structured data over a network connection. It is described in detail by the Internet Engineering Task Force (IETF) in , available at . The DICOM JSON Model complements the XML-based Native DICOM Model, by providing a lightweight representation of data returned by DICOM web services. While this representation can be used to encode any type of DICOM Data Set it is expected to be used by client applications, especially mobile clients, such as described in the QIDO-RS use cases (see ). With the exception of padding to even byte length, a data source that is creating a new instance of a DICOM JSON Model shall follow the DICOM encoding rules in creating Values for the DICOM Attributes within the instance of the DICOM JSON Model. Attribute Values encoded in a DICOM JSON Model are not required to be padded to an even byte length. A data recipient that converts data from an instance of the DICOM JSON Model back into a binary encoded DICOM object shall adjust the padding to an even byte length as necessary to meet the encoding rules specified in DICOM . Amend DICOM PS3.19 as follows (changes to existing text are bold and underlined for additions and struckthrough for removals):

The Native DICOM Model defines a representation of binary-encoded DICOM SOP Instances as XML Infosets that allows a recipient of data to navigate through a binary DICOM data set using XML-based tools instead of relying on tool kits that understand the binary encoding of DICOM. It is not the intention that this form be utilized as the basis for other uses. This form does not take advantage of the self-validation features that could be possible with a pure XML representation of the data. With the exception of padding to an even byte length, a data source that is creating a new instance of a Native DICOM Model (e.g., the result from some analysis application) shall follow the DICOM encoding rules (e.g., the handling of character sets) in creating Values for the DicomAttributes within the instance of the Native DICOM Model. Attribute Values encoded in a Native DICOM Model are not required to be padded to an even byte length. Group Length (gggg,0000) attributes shall not be included in a Native DICOM Model instance. A data recipient that converts data from an instance of the Native DICOM Model back into a binary encoded DICOM object shall adjust the padding to an even byte length as necessary to meet the encoding rules specified in DICOM .