What is a CORE HL7 Definition?

A CORE HL7 Definition is a data programming object which is part of the CORE HL7 API that contains information about a specific HL7 (Health Level 7) version 2.<xx> interface. While HL7 is a world-wide standard maintained at https://www.HL7.org, in the real world sometimes there is a need to build on their ANSI HL7 definitions to accommodate a particular client or system.
 
For HL7 programmers the CORE HL7 Definition can provide both structural and contextual information specifications which can be used both for HL7 syntax validation as well as providing built-in reporting and display information.
 
We (the authors) use the CORE HL7 Definition in our commercial HL7 software like our CORE HL7 Viewer where the definitions provide the HTML Tooltips and reports when you look at a HL7 message. In our UltraPort SQL Schema Engine for HL7 we use the definitions created by the user to provide the HL7 structural specification which guides our algorithms for creating MS SQL and MySQL database tables.
 
For HL7 novices or students this program can provide help and insights as to how HL7 messages are constructed.

In our FREE CORE HL7 Viewer software (see online help for CORE HL7 Viewer) we use the ChooseDefinition() method as shown below in this excerpt from the source code.

CORE HL7 Viewer - Choosing a HL7 Definition

ChooseDefinition() Dialog

Source Code (C#):

               HL7DefinitionManager vMg = new HL7DefinitionManager(LPInternals.MyController);

              //Get the currently selected HL7 Definition

              //NOTE: InstalledVendor is a custom simple wrapper class to hold the

              //HL7Definition object plus some ancillary properties

               InstalledVendor iv = LPInternals.MyVendors.Definition;

              //Get a List of All My HL7 Definitions

               List<HL7Definition> ml = LPInternals.MyVendors.ListOfDefinitions();

              //Set the Selected Definition IF I have one

               HL7Definition sel = null;

              if (iv != null)

               {

                   sel = iv.Definition;

               }

              //Since there's no == operator we'll use the

              //internal VendorID property to tell if they selected the SAME definition

              string selVendorID = iv.Definition.VendorID;

              //Set the HelpURL property so that user has a Help button in the

              //Dialog which points to the online help for this product

               vMg.HelpURL = LPInternals.MainWindowHelpURL;

              //Now launch the dialog

               HL7Definition ob = vMg.ChooseDefinition(this, ml, sel);

              //Now I could just check if ob == null but there's a handy

              //UserCancelled boolean I can use instead.

              if (vMg.UserCancelled) { return; }

              //Did they just choose the SAME definition?

              if (ob.VendorID == selVendorID) { return; }

              //Update the Display using the new definition

               LPInternals.MyVendors.SetDefinition(ob);