Basics of Creating ANSI/INCITS-Compliant Target Files

URC takes care of the generation of URC interface by reading data from XML files. The ANSI/INCITS 389-393 collection of standards, commonly referred to as the URC standard or the V2 standard (the name of the INCITS group that initiated the standard) defines protocols for describing a target and its properties that are implemented by XML (eXtensible Markup Language) files.

The core set of target-based files are four in number. The four files are:

• a socket file, expressed in XML, that presents the signals and their properties, including what signals are available to be controlled and the types of data the signal variables accept or tolerate (ANSI/INCITS 390), see also code fragments below,
• a presentation (PreT) file, expressed in XML, which gives details of the URI references for each of the variables defined in the socket file, including the form of interactors and how variables are grouped (ANSI/INCITS 391),
• a target description file, expressed in XML, which points to locations for all the target files and other discovery information (ANSI/INCITS 392), see also code fragments below,
• a target-based resource description framework (RDF) file, that gives information about what labeling information is available for the controls, help content, alternative formats, etc. (ANSI/INCITS 393), see also code fragments below.

The above diagram gives a pictorial perspective of how the XML files provided by the target device are used by URC. Numbers 1 to 5 give the sequence of actions:

1. URC reads the TD file and locates all other XML files required. If all files are available, a target is supposed to be fully available to the URC.
2. URC reads the socket to get the signals and their data types.
3. URC locates the presentation file and reads it to generate controls for the signals.
4. RDF file gives labelling information for the controls, menus etc. 5. URC now reads the help files and other miscellaneous files to give more inforation for the user.
5. URC dynamically constructs the interface for the target device.

Concept of Medical URC

The RERC-AMI has adopted this ANSI/INCITS standard for medical devices and created a web based simulation environment for a select group of target medical devices. Three different classes of devices were taken into consideration for simulation purposes. These are:

• Vital Signs Monitoring Devices (see also Vital Signs Monitoring Target in stand-alone mode)
• Controls for Examination Tables/Chairs/Beds (see also Exam Tables Target in stand-alone mode)
• Exercise Ergometers (see also Exercise Ergometers Monitoring Target in stand-alone mode)
• CAS-740 Vital Signs Monitor (see also CAS 740 Vital Signs Monitor Target in stand-alone mode)

These target files were created by Dr. Sarma Danturthi, a senior biomedical engineering with the RERC-AMI.

To make things interesting, RERC-AMI has initiated the Health Level 7 ( HL7) standard names into the simulation. HL7 (Version 3.0) standard is an approved medical messaging standard widely used in hospitals and clinical settings.The HL7 standard follows names defined in the SNOMED clinical terms (CT) and these are available to the public via the National Library of Medicine‘s (NLM) meta thesaurus with a secure login. 

An example segment of the target properties file:

<location id="location">
<geocoordinates>
<gml:Point srsName="vital-signs">
<gml:coordinates>10.0, 10.0</gml:coordinates>
</gml:Point>
</geocoordinates>
</location>
<locator type="audio" id="audio-locator"/>
<locator type="visual" id="visual-locator"/>
<locator type="other" id="IRPing">
<extension><rerc:IRPing type="rerc:basicIR"/></extension>
</locator>
<dc:identifier xsi:type="rerc:companyCode">0123456</dc:identifier>
<dcterms:conformsTo>http://www.incits.org/incits392-2005</dcterms:conformsTo>
<dcterms:modified>2005-08-12</dcterms:modified>
<socket id="socket" name="http://www.rerc- ami.org/V2/Simulation/XMLFiles/V2Required">
<!-- In the following line, path is relative -->
<socketDescriptionLocalAt>V2Required/VitalSigns.uiSocket.xml</socketDescriptionLocalAt>
<category taxonomyName="http://www.unspsc.org">41.11.22.00
</category>
</socket>

In this example, the location element of the file contains the geo-coordinates of the target device. The socket element of the file describes where the socket file reference is available for the URC and also gives the name of the socket file as a local path relative to the referenced location.

A segment of socket file XML code is shown below:

<! – Standard type variable -- >
<variable id="Power" type="xsd:boolean">
<dependency read="true()" write="true()" />
</variable>
<! – Derived type variable. See below also -- >
<variable id="Heartrate" type="xsd:HRType">
<dependency read="value('Power') = true()" write="false()" />
</variable>
…
<xsd:simpleType name="HRType" id="idHRtype">
<xsd:restriction base="xsd:decimal">
<xsd:minInclusive value="50"/>
<xsd:maxInclusive value="150"/>
<xsd:totalDigits value="3"/>
<xsd:fractionDigits value="0"/>
</xsd:restriction>
</xsd:simpleType>

In the above listing, Power is Boolean and Heartrate is a derived type from decimal type. There are upper and lower limits for the Heartrate variable and the total digits are 3 without any decimal places to display. The dependency part is self explanatory in both cases.

The following partial listing illustrates an example of a resource description RDF file.

<aResourceDescription>
<AResourceDescription rdf:about="http://www.rerc-ami.org/Medical/V2 /VitalSigns/Socket/Vitalsigns/VitalSigns-label- en.rdf.xml#heartrate_label">
<content rdf:parseType="Literal"><span xml:lang="en">HR</span></content>
<dcterms:conformsTo rdf:resource="http://www.incits.org/incits393-2005"/>
<!-- Socket signal identification here -->
<useContext>
<UseContext>
<elementRef rdf:resource="http://www.rerc-ami.org/Medical
/V2/VitalSigns/Socket#HeartRate" />
<role rdf:resource="http://www.incits.org/incits393-2005#label" />
<languageContext>en</languageContext>
</UseContext>
</useContext>
<!-- Presentation template identifier here -->
<useContext>
<UseContext>
<elementRef rdf:resource="http://www.rerc- ami.org/Medical/V2/VitalSigns/pret#HeartRate" />
<role rdf:resource="http://www.incits.org/incits393-2005#label" />
<languageContext>en</languageContext>
</UseContext>
</useContext>
</AResourceDescription>
</aResourceDescription>

Units of the signal and the font size for the units etc., are similarly described in another <aResourceDescription> node in the RDF. Alternative representations such as images or audio files can also be part of RDF files, as can images such as company logos.