Restore introduction paragraph location and structure

Author: Deep

documents/RWD-Lineage_Data_Standard_Specification.md

@@ -4,9 +4,11 @@
 
 RWD Lineage is a machine-readable CDISC data exchange standard for lineage metadata supplied along with RWD-derived SDTM. It provides the data reliability required by FDA to use RWE as primary evidence.
 
+RWD Lineage is an XML-formatted extension to Define-XML, implemented as a Namespace Extension. It can be embedded directly within Define-XML using a custom tag (e.g., `rwdl:lineage`) or referenced as a separate XML file.
+
 ## Document Structure
 
-An RWD Lineage document has a single root element, `rwdl:lineage`, with exactly two kinds of top-level child:
+An RWD Lineage document has a single root element, `rwdl:lineage`, with exactly two kinds of top-level children:
 
 - **`rwdl:sourceMetadata`** — the *source metadata layer*. A single OPTIONAL element describing the source systems the lineage draws from: their names, the data models or standards they conform to, and the controlled terminologies in which their coded values are encoded. This layer carries *assertions* about the sources.
 - **`rwdl:lineageTrail`** — the *lineage trail*. A single element containing an array of `rwdl:MapID` elements, each a Source–Target pair recording that a value at one physical coordinate became a value at another. This layer carries *forensic facts* about data movement.
@@ -32,8 +34,6 @@ The root element `rwdl:lineage` is the document as a whole; `rwdl:lineageTrail`
 
 The remainder of this specification describes the two layers in turn — first the **Lineage Trail** (the `rwdl:MapID` array and the Coordinate model that addresses values within sources), then the **Source Metadata** layer — followed by the **Controlled Terminology** that governs the enumerated attributes used by both, worked **Examples**, and the mechanism for attaching an RWD Lineage document to **Define-XML**.
 
-RWD Lineage is an XML-formatted extension to Define-XML, implemented as a Namespace Extension. The `rwdl:lineage` document may be embedded directly within Define-XML or supplied as a separate referenced file; see "Attaching RWD Lineage to Define-XML" below.
-
 ## Lineage Trail
 
 The lineage trail is carried in a single `rwdl:lineageTrail` element containing a collection (array) of `rwdl:MapID` elements. Each `rwdl:MapID` contains exactly one Source Coordinate and one Target Coordinate, establishing a direct link between a raw real-world data value and the standardized clinical data value derived from it. The trail is forensic: it records where a value came from, where it went, and — by reference — the transformation applied, without making semantic claims about what the value means.