Health Level 7
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Health Level Seven (HL7), is a non-profit organization involved in the development of international healthcare informatics interoperability standards. "HL7" also refers to some of the specific standards created by the organization (e.g., HL7 v2.x, v3.0, HL7 RIM).
HL7 and its members provide a framework (and related standards) for the exchange, integration, sharing, and retrieval of electronic health information. The 2.x versions of the standards, which support clinical practice and the management, delivery, and evaluation of health services, are the most commonly used in the world.
HL7 is an international community of healthcare subject matter experts and information scientists collaborating to create standards for the exchange, management and integration of electronic healthcare information.
HL7 promotes the use of such informatics standards within and among healthcare organizations to increase the effectiveness and efficiency of healthcare information delivery for the benefit of all.
The HL7 community is organized in the form of a global organization (Health Level Seven, Inc.) and country-specific affiliate organizations:
- Health Level Seven, Inc. (HL7, Inc. ) is headquartered in Ann Arbor, Michigan.
- HL7 affiliate organizations, not-for-profit organizations incorporated in local jurisdictions, exist in over 40 countries. The first affiliate organization was created in Germany in 1993.
The organizational structure of HL7 Inc. is as follows:
- The organization is managed by a Board of Directors, which comprises 10 elected positions and three appointed positions.
- The Chief Executive Officer (currently Charles Jaffe, MD, PhD) serves as an ex officio member of and reports to the Board of Directors. The Chief Technology Officer (currently John Quinn); and the Chief Operations Officer (currently Mark McDougall) report to the CEO and also serve as ex officio members on the Board of Directors.
- Members of HL7 are known collectively as "The Working Group". The Working Group is responsible for defining the HL7 standard protocol and is composed of Standing Administrative Committees and Working Groups.
- Standing Administrative committees focus on organizational or promotional activities, such as Education, Implementation, Marketing, Outreach Committee for Clinical Research, Publishing and Process Improvement and Tooling.
- Working groups are directly responsible for the content of the Standards, framing the actual language of the specifications.
HL7 was founded in 1987 to produce a standard for hospital information systems. HL7, Inc. is a standards organization that was accredited in 1994 by the American National Standards Institute (ANSI).
HL7 is one of several American National Standards Institute accredited Standards Developing Organizations (SDOs) operating in the healthcare arena. Most SDOs produce standards (sometimes called specifications or protocols) for a particular healthcare domain such as pharmacy, medical devices, imaging or insurance (claims processing) transactions. Health Level Seven’s domain is clinical and administrative data.
Today, HL7 has been adopted by several national SDOs outside the United States. Those SDOs are consequently not accredited by ANSI. However, HL7 is now adopted by ISO as a centre of gravity in international standardization and accredited as a partnering organization for mutual issuing of standards. The first mutually published standard is ISO/HL7 21731:2006 Health informatics—HL7 version 3—Reference information model—Release 1.
The name "Health Level-7" 
The name "Health Level-7" is a reference to the seventh layer of the ISO OSI Reference model also known as the application layer. The name indicates that HL7 focuses on application layer protocols for the health care domain, independent of lower layers. HL7 effectively considers all lower layers merely as tools.
HL7 collaborates with other standards development organizations and national and international sanctioning bodies (e.g. ANSI and ISO), in both the healthcare and information infrastructure domains to promote the use of supportive and compatible standards. HL7 collaborates with healthcare information technology users to ensure that HL7 standards meet real-world requirements, and that appropriate standards development efforts are initiated by HL7 to meet emergent requirements.
About 45% of the global membership (of either HL7 Inc. or an HL7 affiliate) is located in Europe, 35% in North America, 15% in Asia-Oceania and 5% elsewhere.
HL7 standards 
Most HL7 standards can now be deemed Open Standards, as since April 2013 they are available for free download. On Sept 4, 2012, the HL7 Board of Directors had announced its intention to relax the HL7 IP policy and allow free access and implementation to promote adoption and interoperability, as described in their press release.
The revenue model and business plan of HL7 is discussed in HL7's Strategic Initiatives and Implementation Proposal. However, since the earlier policy as described in the Bylaws of October 2002 placed the HL7 protocol specifications in the Public Domain, and under 17 USC § 102 there is no copyright protection for an "idea, procedure, process, system, method of operation, concept, principle, or discovery", this revised policy may not be enforceable.
Hospitals and other healthcare provider organizations typically have many different computer systems used for everything from billing records to patient tracking. All of these systems should communicate with each other (or "interface") when they receive new information but not all do so. HL7 specifies a number of flexible standards, guidelines, and methodologies by which various healthcare systems can communicate with each other. Such guidelines or data standards are a set of rules that allow information to be shared and processed in a uniform and consistent manner. These data standards are meant to allow healthcare organizations to easily share clinical information. Theoretically, this ability to exchange information should help to minimize the tendency for medical care to be geographically isolated and highly variable.
HL7 develops conceptual standards (e.g., HL7 RIM), document standards (e.g., HL7 CDA), application standards (e.g., HL7 CCOW), and messaging standards (e.g., HL7 v2.x and v3.0). Messaging standards are particularly important because they define how information is packaged and communicated from one party to another. Such standards set the language, structure and data types required for seamless integration from one system to another.
HL7 encompasses the complete life cycle of a standards specification including the development, adoption, market recognition, utilization, and adherence. HL7 International currently asserts that business use of the HL7 standards requires a paid organizational membership in HL7, Inc. HL7 Members can access standards for free, and non-members can buy the standards from HL7, ANSI, or for some standards, ISO.
The Reference Information Model (RIM) and the HL7 Development Framework (HDF) are the basis of the HL7 Version 3 standards development process. RIM is the representation of the HL7 clinical data (domains) and the life cycle of messages or groups of messages. HDF is a project to specify the processes and methodology used by all the HL7 committees for project initiation, requirements analysis, standard design, implementation, standard approval process, etc.
- Version 2.x Messaging Standard – an interoperability specification for health and medical transactions
- Version 3 Messaging Standard – an interoperability specification for health and medical transactions, based on RIM
- Version 3 Rules/GELLO – a standard expression language used for clinical decision support
- Arden Syntax – a grammar for representing medical conditions and recommendations as a Medical Logic Module (MLM)
- Clinical Context Object Workgroup (CCOW) – an interoperability specification for the visual integration of user applications
- Claims Attachments – a Standard Healthcare Attachment to augment another healthcare transaction
- Clinical Document Architecture (CDA) – an exchange model for clinical documents, based on HL7 Version 3
- Electronic Health Record (EHR) / Personal Health Record (PHR) – in support of these records, a standardized description of health and medical functions sought for or available
- Structured Product Labeling (SPL) – the published information that accompanies a medicine, based on HL7 Version 3
HL7 version 2.x 
The HL7 version 2 standard (also known as Pipehat) has the aim to support hospital workflows. It was originally created in 1989.
HL7 version 2 defines a series of electronic messages to support administrative, logistical, financial as well as clinical processes. Since 1987 the standard has been updated regularly, resulting in versions 2.1, 2.2, 2.3, 2.3.1, 2.4, 2.5, 2.5.1 and 2.6. The v2.x standards are backward compatible (e.g., a message based on version 2.3 will be understood by an application that supports version 2.6).
HL7 v2.x messages use a human-readable (ASCII), non-XML encoding syntax based on segments (lines) and one-character delimiters. Segments have composites (fields) separated by the composite delimiter. A composite can have sub-composites (subcomponents) separated by the sub-composite delimiter, and sub-composites can have sub-sub-composites (subcomponents) separated by the sub-sub-composite delimiter. The default delimiters are vertical bar or pipe (|) for the field separator, caret (^) for the component separator, and ampersand (&) for the subcomponent separator. The tilde (~) is the default repetition separator. The first field (composite) in each segment contains the 3-character segment name. Each segment of the message contains one specific category of information. Every message has MSH as its first segment, which includes a field that identifies the message type. The message type determines the expected segment names in the message. The segment names for a particular message type are specified by the segment grammar notation used in the HL7 standards.
The following is an example of an admission record. MSH is the header record, PID the Patient Identity, etc. The 5th field for the PID record is the patients name.
PID|||56782445^^^UAReg^PI||KLEINSAMPLE^BARRY^Q^JR||19620910|M||2028-9^^HL70005^RA99113^^XYZ|260 GOODWIN CREST DRIVE^^BIRMINGHAM^AL^35 209^^M~NICKELL’S PICKLES^10000 W 100TH AVE^BIRMINGHAM^AL^35200^^O |||||||0105I30001^^^99DEF^AN
PV1||I|W^389^1^UABH^^^^3||||12345^MORGAN^REX^J^^^MD^0010^UAMC^L||678 90^GRAINGER^LUCY^X^^^MD^0010^UAMC^L|MED|||||A0||13579^POTTER^SHER MAN^T^^^MD^0010^UAMC^L|||||||||||||||||||||||||||200605290900
DG1|1||786.50^CHEST PAIN, UNSPECIFIED^I9|||A
HL7 v2.x has allowed for the interoperability between electronic Patient Administration Systems (PAS), Electronic Practice Management (EPM) systems, Laboratory Information Systems (LIS), Dietary, Pharmacy and Billing systems as well as Electronic Medical Record (EMR) or Electronic Health Record (EHR) systems. Currently, HL7’s v2.x messaging standard is supported by every major medical information systems vendor in the United States.
HL7 version 3 
The HL7 version 3 standard has the aim to support all healthcare workflows. Development of version 3 started around 1995, resulting in an initial standard publication in 2005. The v3 standard, as opposed to version 2, is based on a formal methodology (the HDF) and object-oriented principles.
RIM - ISO/HL7 21731
The Reference Information Model (RIM) is the cornerstone of the HL7 Version 3 development process and an essential part of the HL7 V3 development methodology. RIM expresses the data content needed in a specific clinical or administrative context and provides an explicit representation of the semantic and lexical connections that exist between the information carried in the fields of HL7 messages. The RIM is essential to increase precision and reduce implementation costs. Models are available.
HL7 Development Framework - ISO/HL7 27931
The HL7 Version 3 Development Framework (HDF) is a continuously evolving process that seeks to develop specifications that facilitate interoperability between healthcare systems. The HL7 RIM, vocabulary specifications, and model-driven process of analysis and design combine to make HL7 Version 3 one methodology for development of consensus-based standards for healthcare information system interoperability. The HDF is the most current edition of the HL7 V3 development methodology.
The HDF not only documents messaging, but also the processes, tools, actors, rules, and artifacts relevant to development of all HL7 standard specifications. Eventually, the HDF will encompass all of the HL7 standard specifications, including any new standards resulting from analysis of electronic health record architectures and requirements.
HL7 specifications draw upon codes and vocabularies from a variety of sources. The V3 vocabulary work ensures that the systems implementing HL7 specifications have an unambiguous understanding of the code sources and code value domains they are using.
The HL7 version 3 messaging standard defines a series of electronic messages (called interactions) to support all healthcare workflows. HL7 v3 messages are based on an XML encoding syntax.
Clinical Document Architecture - ISO/HL7 27932 
Methods applied by HL7 
Services Aware Interoperability Framework 
The HL7 Services-Aware Enterprise Architecture Framework (SAIF) provides consistency between all HL7 artifacts, and enables a standardized approach to Enterprise Architecture (EA) development and implementation, and a way to measure the consistency.
SAIF is a way of thinking about producing specifications that explicitly describe the governance, conformance, compliance, and behavioral semantics that are needed to achieve computable semantic working interoperability. The intended information transmission technology might use a messaging, document exchange, or services approach.
SAIF is the framework that is required to rationalize interoperability of other standards. SAIF is an architecture for achieving interoperability, but it is not a whole-solution design for enterprise architecture management.
Arden syntax 
The Arden syntax is a language for encoding medical knowledge. HL7 adopted and oversees the standard beginning with Arden syntax 2.0. These Medical Logic Modules (MLMs) are used in the clinical setting as they can contain sufficient knowledge to make single medical decisions. They can produce alerts, diagnoses, and interpretations along with quality assurance function and administrative support. An MLM must run on a computer that meets the minimum system requirements and has the correct program installed. Then, the MLM can give advice for when and where it is needed.
A large portion of HL7 messaging is transported by Minimal Lower Layer Protocol (MLLP), also known as Lower Layer Protocol (LLP). For transmitting via TCP/IP, header and trailer characters are added to the message to identify the beginning and ending of the message because TCP/IP is a continuous stream of bytes. Hybrid Lower Layer Protocol (HLLP) is a variation of MLLP that includes a checksum to help verify message integrity. Amongst other software vendors, MLLP is supported by Microsoft and Oracle.
CCOW, or "Clinical Context Object Workgroup," is a standard protocol designed to enable disparate applications to share user context and patient context in real-time, and at the user-interface level. CCOW implementations typically require a CCOW vault system to manage user security between applications.
Functional EHR and PHR specifications 
Functional specifications for an electronic health record.
Country specific aspects 
HL7 Australia was established in 1998.
Australia was an early adopter of the HL7 V2.x standards, which are now used ubiquitously in Australian public and private healthcare organisations.
The localisation of the HL7 standards is undertaken in cooperation with the national standards body, Standards Australia.
HL7 Australia closely cooperates with the National E-Health Transition Authority (NEHTA).
- HL7 Australia
- Standards Australia (IT-014 "Health Informatics")
- National E-Health Transition Authority (NEHTA)
Australia has been selected to host the International HL7 Interoperability Conference in 2013. This will be a two day event in Sydney from 28th – 30th October 2013.
Proposed themes for the event include:
• HL7/FHIR (Fast Healthcare Interoperability Resources),
• CDA implementation and innovation,
• Leveraging HL7v2.x investment, and
• Emerging developments: CIMI, clinical terminology & semantic web
HL7 within Canada is supported by the HL7 Canadian Constituency, which is hosted by the Canadian Health Infoway Standards Collaborative.
Among its support for domestic and international activities are:
- Liaising with HL7 International;
- Supporting communication and correspondence domestically and international for specific HL7 items;
- Responding to inquiries from HL7 International;
- Planning and execution of HL7 Canada Constituency roles and responsibilities;
- Supporting domestic and international HL7 Canada meetings;
- Providing support to domestic input on international HL7 ballot and comment items; and
- Administering the HL7 Canada Constituency forum to facilitate member collaboration.
Notable HL7 implementations currently include Prince Edward Island's drug information system (DIS).
National Health Archive http://www.kanta.fi/en
The Social Insurance Institution of Finland, together with other health and welfare bodies in Finland have been rolling out a national health care database based on HL7 CDA R2 and V3 messages. The system is knonn by the acronym KanTa which is an abbreviation of KANsallinen TerveysArkisto (National Health Archive). The word KANTA in Finnish means "base", "stem" or "heel".
Currently (as at February 2013) the system holds details of all electronic prescriptions and all pharmacies in Finland are connected to the database. The system enables prescriptions to be written by any medically qualified doctor into the system and enables the patient to collect prescriptions from any pharmacy nationwide. Citizens can log into the system via the internet using an authentication service and see their own record. There is a choice of using a government controlled authorization system or using the same authentication service used for on-line banking. These services use one-time (i.e. non repeating log in identifiers) which minimizes the risk of phishing or other intercepts. By logging into the system, the patient can see what medicines have been prescribed, which doctor prescribed them and when, what prescriptions have been collected from which pharmacy and on which date, and what the price paid was. The latter is useful for patients taking expensive medications because there is a national ceiling on patient medical costs so that the government will 100 % of costs over the ceiling under the social insurance program. The record also shows what the dose should be, the name of the doctor who prescribed the medication, and what quantities of prescribed medications are still available for collection, subject to controls around the amount of medication is allowed to store at home. The system alerts doctors and pharmacies to prevent simultaneous use of incompatible medicines. For regular prescriptions, when the last prescription is fulfilled, the pharmacist can ask the patient if he would like the doctor to be asked to repeat issue the prescription. If yes, the pharmacy issues the request electronically and the doctor must either renew, modify, or terminate the prescription within 8 days. The patient can choose to receive a text message to his/her mobile phone advising of the outcome.
Still being rolled out is the second phase of the project which is to enable the national database to be used to store other patient medical records. This is subject to the patient consenting for the transfer of data from his home health service station into the national archive. Patients thus have control over their own records, though most are expected to see the benefits of having their records in a permanently available national register.
Version 2 HL7 messaging is widely deployed in most hospitals and healthcare centers. CDA R1 is used in sharing patient records on a regional level.
- HL7 Finland national affiliate
The German chapter of HL7 was founded in 1993. This is an entity for benefit to the public and registered as an association as HL7 e. V.
Due to federal structure of operational administration in German healthcare, the standardization aspect is much behind the possibilities of the public economy and due to competitive interests in industry of low normative impact to healthcare information systems development. Currently HL7 in Germany operates as an informal cluster and collaborates with the national standardization body.
The voluntary membership in HL7 relies on personal interest and engagement of clinical users and mainly on industrial interest: Clinical memberships are in minority. There is low membership of governmental administration and thus low contribution to ongoing discussion e.g. on patient data records (EPA = elektronische Patientenakte) balancing data availability vs. data security. Impact on productivity for hospital information systems (called KIS = Krankenhaus-Informationssysteme in German) is of no importance yet, as the variability of HIS systems has not been challenged by HL7.
Governmental funding for a broader adoption of HL7 does yet not exist in Germany, neither on federal level nor in most of the regional governments.
HL7 India is active in conducting e-learning courses for HL7 and HL7 certification examinations.
- HL7 India
HL7 Italia was established in 2003 and it is responsible for the localization of this standard in the Italian context. The aim is to stimulate and direct the regional and national contributions towards the standard development and to promote the modernization of Italian health IT.
HL7 Italia members are suppliers of health IT market. Some Italian regions, regional In-Houses, Governative Agencies, Public Research Institutes, local Hospital departments and individual IT professionals are HL7 Italia members.
- HL7 Italia
The Netherlands 
AORTA - National Healthcare ICT infrastructure
AORTA is the Dutch national infrastructure for the exchange of data between healthcare providers. AORTA uses HL7 version 3 messages and documents as its core mechanism for information exchange. The initial specifications were created in 2003. The Dutch Ministry of Health is working on a virtual national Electronic Patient Records (EPR) which will enable healthcare providers to share patient data. This development takes place in close collaboration with Nictiz, the National Information and Communication Technology Institute for Healthcare. Nictiz coordinates its efforts with regard to the usage of HL7 version 3 with the volunteers of HL7 the Netherlands.
Almost all hospitals use HL7 version 2 to support hospital-internal workflows. EDIfact is being used to support workflows involving general practitioners (GPs/PCPs). EDIfact will be slowly replaced by HL7 version 3.
- HL7 the Netherlands
- National Information and Communication Technology Institute for Healthcare (Nictiz)
- AORTA whitepaper
HLH - Health Life Horizon
HLH (a national project) is being carried out at School of Electrical Engineering and Computer Sciences of National University of Sciences and Technology and is supported by Government of Pakistan with funds provided by National ICT R&D Fund. HLH basic theme is to target health care information exchange and interoperability using HL7 version 3. Though the penetration and use of HL7 in Pakistan is lower than the countries like US and that of Europe. But its getting popularity among the stakeholders in Pakistan. HLH Team members have been participating in HL7 International Working Group meetings and conferences for last two years. On Oct 1, 2010 HL7 International formally announced the Pakistan Chapter at the 24th Plenary and WGM in Cambridge, MA, USA. Pakistan is now the 37th affiliate of HL7 International around the world. HL7 Pakistan is now officially authorized to give memberships to local organizations along with other privileges like certification, training, etc.
The Certification Commission for Healthcare Information Technology (CCHIT) has developed an open-source program called Laika to test EHR software for compliance with CCHIT interoperability standards.
HL7’s initial involvement in the Health Insurance Portability and Accountability Act (HIPAA) legislation began in 1996 with the formation of the Attachments special interest group to standardize the supplemental information needed to support health care insurance, and other e-commerce transactions. The initial deliverable of this group was a set of six recommended Claims Attachments for the Notice of Proposed Rule Making (NPRM) process. Future attachment projects include, but are not limited to, Home Health, Skilled Nursing Facility, durable medical equipment (DME), end stage renal disease (ESRD), and Pre-Authorization and Referrals. The Attachment special interest group is responsible for implementing the Administrative Simplification provisions of HIPAA mandates, providing on-going support, and representing HL7 in the Designated Standards Maintenance Organization (DSMO) efforts. Its purpose is to encourage the use of HL7 for uniform implementation of this supplemental information. This SIG coordinates industry input to produce and maintain guides for HL7 messages that can stand alone or be embedded within ANSI X12 transactions.
ARRA and HITECH
The American Recovery and Reinvestment Act of 2009 (ARRA) and Health Information Technology for Economic and Clinical Health Act (HITECH) legislation specified HL7 versions 2.3.1 and 2.5.1, and the HL7 Continuity of Care Document (CCD), as the healthcare standards to meet certain certification requirements.
See also 
- Clinical Document Architecture (CDA)
- Electronic medical record
- European Institute for Health Records (European Union)
- Gello Expression Language
- Health Informatics
- Health Informatics Service Architecture (HISA)
- Healthcare Services Specification Project (HSSP)
- HL7 SAIF
- ISO TC 215
- Mirth (software)
- openEHR Foundation
- Public Health Information Network
- SNOMED, SNOMED CT
- "About Health Level Seven". Health Level Seven.
- "Healthcare Interoperability Glossary". Corepoint Health.
- Shaver, Dave. "The HL7 Evolution - Comparing HL7 Versions 2 and 3". Corepoint Health. Retrieved 16 February 2012.
- "Health Level Seven International". HL7.
- "Contact Health Level Seven". Health Level Seven.
- http://www.ansi.org/ ANSI
- "HL7 Membership Numbers". 2007-11-08. as sent to the HL7 affiliates.
- "HL7 International Standards Available at No Cost".
- Lucas Mearian (Sept 4, 2012). "HL7 e-health information-sharing standard to be free". Computerworld.
- "HL7 Standards Soon to be Free of Charge". HL7. Sept 4, 2012.
- "Free IP FAQ". HL7. Sept 4, 2012.
- "HL7 Strategic Initiatives and Implementation Proposal".
- "Bylaws of Health Level Seven, Inc. (as still posted 2004/07/08)".
- "17 USC § 102 Subject matter of copyright".
- "California Clinical Data Project: CALINX Standards". California HealthCare Foundation. March 2011.
- "HL7 Reference Information Model". HL7.
- "HL7 Development Framework (HDF)". HL7.
- "HL7 Standards". HL7.
- "HL7 FAQs". HL7.
- "Understanding HL7 Messages". iNTERFACEWARE.
- "HL7 Messages and Descriptions". iNTERFACEWARE.
- "Standards Organizations". Assistant Secretary for Planning and Evaluation (ASPE), Health and Human Services (HHS).
- "Tools & Resources – V3 Modeling & Methodology Tools". HL7.
- The CDA Book.
- "LLP - Lower Layer Protocol". iNTERFACEWARE.
- "MLLP Receive and Send Components". MSDN.
- "Oracle Application Server Integration B2B User's Guide, Supported Protocols". Oracle.
- "Standards Australia eHealth". Standards Australia.
- "National E-Health Transition Authority". National E-Health Transition Authority.
- "HL7 Canada". FAQ. Canada Health Infoway. Retrieved 24 November 2011.
- "HL7 Finland -esite". HL7 Finland ry.
- "DIN NAMed Jahresbericht 2007". Deutsches Institut für Normung e. V. (DIN). 2007.
- "HL7 Healthcare Standard Institute". HL7 India.
- "HL7 Italia". HL7 IT.
- "Onze organisatie HL7". HL7 Nederland.
- "Nictiz (National Information and Communication Technology Institute for Healthcare)". Nictiz.
- "AORTA, the Dutch national infrastructure". Ringholm.
- "HLH Team Member Participation in HL7 plenary meeting for signing agreement of HL7 Pakistan with HL7 International at Cambridge, US". Pakistan: National University of Sciences & Technology.
- "Health Life Horizon". Pakistan: National University of Sciences & Technology.
- "HL7 Pakistan". HL7 Pakistan.
- "Health Insurance Reform: Announcement of Designated Standard Maintenance Organizations". Department of Health and Human Services, Health Care Financing Administration. August 17, 2000.
- "Versions of the HL7 Standard". Corepoint Health.
- HL7 Standards
- HL7.org site
- Introduction to HL7
- How does HL7 work? (Video Introduction)
- HL7.org EHR Page
- Fast Healthcare Interoperability Resources (FHIR)
- What does HL7 enablement means?
- HL7 is a member of the Joint Initiative on SDO Global Health Informatics Standardization
- HL7 Tools Page
- Australian Healthcare Messaging Laboratory (AHML) - Online HL7 Message Testing and Certification
- Comprehensive Implementation of HL7 v3 Specifications in Java
- HL7 Programming Tutorial using Java
- HL7 101: A Beginner’s Guide
- International HL7 Experts Consortium
- The Healthcare IT Interoperability Blog
- NIST HL7 Conformance Testing Framework
- ICH-HL7 Regulated Product Submissions
Critical reviews 
- HL7 RIM: An Incoherent Standard and The HL7 RIM Under Scrutiny - rebuttal
- HL7 Watch – Blog; critical review of HL7. See also the posted comments for attempted rebuttals to some of the earlier posts.
Open source tools 
There are a number of FOSS based tools that can foster worldwide adoption of the HL7 standards
- The HL7 Tools Directory lists many FOSS tools and resources
- Mirth Connect, an Open Source HL7 Integration Engine for HL7 V2/V3, DICOM, NCPDP and X12. Freely available under MPL 1.1 license
- The open health tools consortium
- The HL7 Java Special Interest Group's implementation of HL7 v3
- The Eclipse OHF project - v2 and v3 implementations (IDE type tools and run-time libraries)
- HAPI, An open-source, object-oriented HL7 2.x parser for Java
- The Perl HL7 Toolkit, an Open-Source HL7 Perl module
- Pear (PHP) HL7 messaging API module
- The eXcessively Simple HL7 v2 Processing Platform using XML and XSLT
- The Ruby HL7 Library
- HL7 Java binding
- nule.org HL7 Utilities
- nHAPI open-source library for .NET
- HL7v3 Messaging Framework for .NET
- HL7 Analyst for .NET
- HL7Kit Free Sender, HL7 Message Editor and Sender