# 6.1 Representations Overview

 Topic Version 1 Published 09/11/2015 Topic Change History For Standard RESQML v2.0.1

Representations of different business objects (e.g., a horizon versus a reservoir versus a seismic survey) have different requirements and elements. However, all RESQML representations share several common concepts. This chapter explains these shared concepts, which include:

Representations of different business objects (e.g., a horizon versus a reservoir versus a seismic survey) have different requirements and elements. However, all RESQML representations share several common concepts. This chapter explains these shared concepts, which include:

• Indexable elements (see 6.2 Indexing ). Geometric or topological elements in a representation that can be enumerated by a contiguous set of integral numbers, which are called indices. The indices are used to uniquely specify how properties and geometry are associated with elements in a representation. A subset of indexable elements can be identified by an ordered subset of indices (i.e., a subrepresentation). Indices can be multi-dimensional.
• Patches (see 6.3 Patches ). A Patch is a mechanism in RESQML that lets you specify topology and geometry to define independent parts of one representation; together all patches belonging to a representation constitute the entire representation. Using Patches is a way to hierarchically organize a representation into several parts, because inside a representation you have an ordered list of patches (each patch containing some elements). For example, the triangulated representation of a horizon may consist of 10 triangulated patches. To correctly order the geometry or properties on this representation, the software importing or reading that horizon must know the indices within each of the 10 triangulated patches AND how the 10 triangulated patches are sequenced.
• Subrepresentations (see Section 6.4). A subrepresentation is a logical and ordered subset of one or several existing representations. It is itself a representation. Subrepresentations are used to define the topological elements of new representations that get their geometry from some previously defined existing representations (which means they avoid geometry redundancy).
• Representation identities (see 6.5 Representation Identities . Relationships (or semantics) between nodes of representation or subrepresentations.