# 10.2.3.2 Polyline Set Representations

Topic Version | 1 | Published | 09/11/2015 | |

For Standard | RESQML v2.0.1 |

For better data transfer performance (more compact datasets), polylines and polygonal chains can be assembled into polyline set representations. In sets, each single polyline embedded into the set representation has an implicit topology. This topology consists of attaching the nodes in sequence by following the order of the nodes contained in a point 3D HDF5 array, which inherits from the abstract point 3D array.

A polyline set representation has two pieces of explicit topological information:

- The number of nodes for each polyline
- A Boolean to indicate if a polyline embedded into the set is closed or not
- When the “closed polyline” Boolean is true, the first and the last point of the given polyline are identical (the X,Y,Z value are repeated).

Note that the topological relationships between the polylines within in a set are NOT explicit. Reader software can read them in the order in which they are stored, but that order may not be important.

Polyline or Polyline Set Roles. The software writer can specify a role for these polylines from this list: fault center line, pick, inner ring, outer ring, trajectory, interpretation line, contact, depositional line, erosion line, contour line, or pillar.