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- The ability to use proportional fonts and have control of font sizes and weights/colours to enable appropriate emphasis to be given to critical abnormalities in the report. Currently only highlight is supported in HL7 Free Text (FT).
- Reliable representation of tabular data which otherwise requires the use of spaces with a non-proportional font. The character width is usually assumed to be around 78 characters, but this is not specified or reliably supported and word wrapping of tabular formatted data impacts severely on its readability.
- The ability to represent a containership hierarchy for highly nested data with appropriate headings
- The ability to embed images into the report where the image data is in the HL7 messages
- The ability to include hyperlinks to internal and external information
- A means of identifying header and footer data such as letterhead information and allowing this to be optionally displayed.
- Existing standard that is widely supported across operating systems.
- Good tolerance for displays of variable size and resolution with mechanisms for users to alter display size.
- The availability of screen readers for disabled users.
- Freely available validation services
- Wide availability of tools for authoring content and formatting of display.
- Text based format that remains searchable and human readable and is small in size.
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In order to reduce the potential for exploits and reduce the overhead, reliability and longevity of the display segments the following constraints must be followed.
1. No JavascriptJavaScript
The HTML display must not use any javascript JavaScript whatsoever in the document either as directly embedded javascript JavaScript or script tags in the header. It is suggested that javascript JavaScript processing be turned off in the display.
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The use of a HTML display segment allows rich formatting of both text and images, but the images are not embedded in the HTML and need to be linked back to the binary image data in the message. The images can be in either ED or RP OBX value type segments. The convention for the url URL format is "hl7v2://OBX.<setID>" eg e.g. if the OBX with a SetID of 4 contains an image the url URL would be "hl7v2://OBX.4". This will need to be handled on the display control or the URL converted to a file based URL and the OBX data extracted to a file. Images, other than in the letterhead divs, should not be linked to external URLs. It is permissible to provide links to external images in the report body but this should be done with a click-able link that the user has to manually select. These external links may well become invalid with time and their external links should be an adjunct to the report and not the entire report contents.
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- The ED datatype supports images in OBX segments.
- Web hyperlinks should optionally be implemented using the RP datatype.
- Receivers must be able to access web references and the ongoing availability of of the data should be considered.
- For pathology data retention refer to the NPAAC guidelines.
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