Standard and Custom Schemas
The HL7 version 2 standard includes a number of different schemas (also frequently known as versions or categories). Each schema defines a set of messages and associated structures. The different schemas reflect the evolution of the standard over time. Ensemble includes the current set of standard schemas. Ensemble uses these schemas to validate HL7 data as well as to parse and display HL7 data.
Ensemble also allows you to define your own custom schemas. Generally, you will define a custom schema relative to a particular standard HL7 schema (called the base schema). The custom schema will consist of modifications to a number of the message structures defined in the standard schema. The most common customization is the addition of custom Z segmentsto the end of a message structure. Once you create a custom schema, Ensemble will use it just as it uses the standard schemas. It can validate HL7 data against the custom schema as well as parse and display HL7 data using the custom schema.
By convention, the names of custom segments begin with the letter "Z", hence "Z segment", for example ZEK, ZPM, ZAL, and so on. Also by convention, Z segments are included at the end of a custom message and trail the standard segments.