but not role composition Domain and range constraints Existential but not universal restriction A restricted form of role inclusion axiom (xRy ^ ySz => xRz) General Concept Inclusion axioms (A ⊆ B). For understanding the modelling, it is also important to look at the stated view of a concept versus the inferred view of the concept. In further considering the state view, SNOMED CT used in the past a modelling approach referred to as 'proximal parent' approach. After 2015, a superior approach called "proximal primitive parent" has been adopted. Precoordination and postcoordination SNOMED CT provides a compositional syntax that can be used to create expressions that represent clinical ideas which are not explicitly represented by SNOMED CT concepts. This mechanism exists because it is challenging to create and maintain all possible concepts upfront (as precoordinated concepts). For example, there is no explicit concept for a "third degree burn of left index finger caused by hot water". However, using the compositional syntax it can be represented as 284196006 | burn of skin | : 116676008 | associated morphology | = 80247002 | third degree burn injury | , 272741003 | laterality | = 7771000 | left | , 246075003 | causative agent | = 47448006 | hot water | , 363698007 | finding site | = 83738005 | index finger structure Such expressions are said to have been 'postcoordinated'. Post-coordination avoids the need to create large numbers of defined Concepts within SNOMED CT. However, many systems only allow for precoordinated representations. Reliable analysis and comparison of post-coordinated expressions is possible using appropriate algorithms machinery to efficiently process the expression taking account of the underlying description logic. Major Electronic Health Record Systems (EHRS) have repeatedly complained to IHTSDO and other standards organizations about the "complexity" of post-coordinated expressions. For example, the postcoordinated expression above can be transformed using a set of standard rules to the following "normal form expression" which enables comparison with similar concepts. 64572001 | disease | : 246075003 | causative agent | = 47448006 | hot water | , 363698007 | finding site | = ( 83738005 | index finger structure | : 272741003 | laterality | = 7771000 | left | ) , { 116676008 | associated morphology | = 80247002 | third degree burn injury | , 363698007 | finding site | = 39937001 | skin structure | } Postcoordination is an important desirable feature of a