gml:Curve 

A curve is a 1-dimensional primitive. Curves are continuous, connected, and have a measurable length in terms of the coordinate system. 
A curve is composed of one or more curve segments. Each curve segment within a curve may be defined using a different interpolation method. The curve segments are connected to one another, with the end point of each segment except the last being the start point of the next segment in the segment list.
The orientation of the curve is positive.
The element segments encapsulates the segments of the curve.

Element Information

Model

gml:metaDataProperty* , gml:description{0,1} , gml:descriptionReference{0,1} , gml:identifier{0,1} , gml:name* , gml:segments
Children: gml:description, gml:descriptionReference, gml:identifier, gml:metaDataProperty, gml:name, gml:segments

Attributes

QName Type Fixed Default Use Inheritable Annotation
axisLabels gml:NCNameList optional
gml:id ID required 
The attribute gml:id supports provision of a handle for the XML element representing a GML Object. Its use is mandatory for all GML objects. It is of XML type ID, so is constrained to be unique in the XML document within which it occurs.
srsDimension positiveInteger optional
srsName anyURI optional
uomLabels gml:NCNameList optional

Source 

<element name="Curve" type="gml:CurveType" substitutionGroup="gml:AbstractCurve">
  <annotation>
    <documentation>A curve is a 1-dimensional primitive. Curves are continuous, connected, and have a measurable length in terms of the coordinate system. A curve is composed of one or more curve segments. Each curve segment within a curve may be defined using a different interpolation method. The curve segments are connected to one another, with the end point of each segment except the last being the start point of the next segment in the segment list. The orientation of the curve is positive. The element segments encapsulates the segments of the curve.</documentation>
  </annotation>
</element>

Sample