Remove ISD, see #4

README.md

@@ -39,7 +39,7 @@ DASH segments are typically of constant duration and aligned across audio and vi
 
 #### Need for TTML post-processing
 
-In above workflow it may be difficult for tools that have only simple TTML capabilities, to process a TTML document for the purpose of creating small, self contained, non overlapping TTML documents (sometimes called intermediate synchronic document, ISD). The example below shows a TTML document with successive `p` elements overlapping in time. 
+In above workflow it may be difficult for tools that have only simple TTML capabilities, to process a TTML document for the purpose of creating small, self contained, non overlapping TTML documents. The example below shows a TTML document with successive `p` elements overlapping in time. 
 
 ```xml
 <?xml version="1.0" encoding="UTF-8"?>
@@ -67,7 +67,7 @@ In above workflow it may be difficult for tools that have only simple TTML capab
 </tt:tt>
 ```
 
-Some workflows may decide that the TTML Authoring tool will post-process the TTML content to produce those ISD with a fine granularity to support the smallest segment duration and take care of timebase conversions. Such a post-processing tool would make the task of tools down the chain easier. Other workflows may decide to leave the segmentation to tools down the chain like the DASH packager because the segment duration is only known at that level in the workflow. Yet other workflows may use tools in-between to make the TTML authoring DASH-unuware and the DASH processing TTML-unaware. Depending on the design choice, the interface between the tools in the workflow will not be the same.
+Some workflows may decide that the TTML Authoring tool will post-process the TTML content to produce those non overlapping TTML documents with a fine granularity to support the smallest segment duration and take care of timebase conversions. Such a post-processing tool would make the task of tools down the chain easier. Other workflows may decide to leave the segmentation to tools down the chain like the DASH packager because the segment duration is only known at that level in the workflow. Yet other workflows may use tools in-between to make the TTML authoring DASH-unuware and the DASH processing TTML-unaware. Depending on the design choice, the interface between the tools in the workflow will not be the same.
 
 #### Interface between MP4 Parser and TTML Renderer
 The MP4 standard assumes that only one sample at a time is active. This means that the MP4 parser will deliver one TTML document at a time to the TTML renderer and will assume that the previous TTML document will be replaced by the new one, and that it will be used for a given duration. This standard behavior thus constrains the upper part of the workflow, in the sense that samples cannot overlap and therefore the contained TTML document should not overlap. This improves interoperability by reducing the number of choices left.