Version 3 - Frequently Asked Questions

DISCLAIMER: The NEMSIS Version 3 FAQs are subject to modification without notification.

Welcome the FAQs section of the NEMSIS v3 section. As the center receives questions from both EMS agencies and software developers, we will try to update this section. If you have any questions, please feel free to contact the NEMSIS Technical Assistance Center. We will try to update this section as often as possible.


Click here for the comprehensive NEMSIS V3 FAQs

General Questions



Question: What is the NEMSIS Version 3 Standard?

A: The National EMS Information System (NEMSIS) Version 3 is an EMS industry data standard which is capable of describing EMS from an operational, service delivery, and patient care perspective.  NEMSIS Version 3 is comprised of a data dictionary with 574 data elements, a data exchange standard using XML, and business logic validation method using Schematron, and an automated exchange method using web-services.  EMS Software that has fully implemented the NEMSIS Version 3 Standard may be tested through the NEMSIS Technical Assistance Center for compliance.  Details on NEMSIS Version 3 can be found at www.nemsis.org.

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Question: What is NEMSIS Version 3 Data Dictionary?

A: The NEMSIS Version 3 Data Dictionary is a document describing in detail each of the 578 Version 3 Data Elements.  The Data Dictionary is a consolidated source of information for each data element including but not limited to:

  • Data Element Name
  • Data Element Number
  • Data Element State and National Status
  • Data Element Definition
  • Version 2 Data Element Number (if migrated from NEMSIS Version 2)
  • Data Structure
    • Usage
    • Recurrence
    • NOT Values
    • Pertinent Negative Values
    • Nillable
  • Associated EMS Performance Measures
  • Data Element Values and Constraints
    • Codes & Descriptions
    • Minimal Values
    • Maximum Values
    • Maximum Data Length
    • Total Digits
    • Decimal Digits
    • Attributes
    • Correlation ID
  • Data Element Comments and Descriptors

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Question: What is Schematron?

A: Schematron is an international standard that compares data within XML documents using a language known as XPath.  Schematron can be categorized as a schema language, a rules language, or a constraint language. It is design to co-exist and augment existing schema languages, providing a convenient way to easily express and test business and structural logic and constraints.  NEMSIS Version 3 uses Schematron to enforce standardized business logic at the time of data entry.  This improves data quality and completeness.  Schematron can be used to generate both error and warning messages back to the user to address before the EMS record or patient care report is finalized.

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Question: What is XML?

A: XML is an acronym for EXtensible Markup Language.  It is an open standard for describing data approved by the W3C. XML uses a similar tag structure as HTML (used in all web page content); however, whereas HTML defines how elements are displayed, XML defines what those elements contain. By providing a common method for identifying data, XML supports business-to-business transactions and has become "the" format for electronic data interchange and Web services.  Detailed information on XML can be found at www.w3.org.

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Question: What is an XSD?

A: XSD is an acronym for XML Schema Definition.  It is the informal name for the XML schema from the W3C open standard.  The XML Schema is used to validate and assure the content of an XML file based on the schema has been provided in the correct format and structure.  The NEMSIS Version 3 XSD is required to enable the exchange of EMS data between disparate EMS data systems.

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Question: What is Web-Services?

A: Web services are Web based applications that use open, XML-based standards and transport protocols to exchange data between two data systems.  It is based on a W3C open standard.  The NEMSIS Version 3 Web Services implementation provides for secure automated data exchange between any NEMSIS Version 3 Compliant data system or data source using the NEMSIS Version 3 Standard.  This could be data submission (export) to a billing software or State EMS Data System.  Web Services also provides a mechanism for EMS software to receive (import) data from medical devices, dispatch centers, or other EMS data systems.

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Question: Why are the cross reference elements Usage (Mandatory, Required, Recommended, Optional) for the Medical Device and CAD XSDs different than those in the EMS XSD

A: The Usage (Mandatory, Required, Optional) for the reference elements within Medical Device and CAD XSDs has to be different (can't be Mandatory or Required in general) because they have to function across a broad range of devices, many of which do not have data entry capability. The Usage type should not and cannot be the same as within the EMS XSD.

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Question: Is XPath required for use with Schematron?

A: Yes, due to the complexity of the NEMSIS rule set there is a requirement to use XPath 2.0

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Question: What will be tested for custom elements as part of compliance testing? Will it just be the sample ones? (Added 1-23-2013)

A: Yes, the sample ones from the NEMSIS website will be utilized located on the following web page: http://nemsis.org/v3/downloads/testCasesXMLSamples.html

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Question: Will the [custom element] IDs be distinct and what will they look like? (Added 1-23-2013)

A: IDs will be distinct. However, the structure has not been defined at the moment.

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Question: How will vendors be alerted to [custom element] changes? How often? (Added 1-23-2013)

A: Custom elements will be posted on a NEMSIS web page. We have not singled out a method for alerting the community to changes. We are looking at implementing a state subscription where one may choose what states to receive updates from. In addition, we may offer a subscription to the general custom element library web page currently in development. Therefore, when a new custom element is released it is available for everyone to access.

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