To: "Henry S. Thompson (University of Edinburgh)" <ht@cogsci.ed.ac.uk>, "David Beech (Oracle Corp.)" <dbeech@us.oracle.com>, "Murray Maloney (Commerce One)" <murray@muzmo.com>, "Noah Mendelsohn (Lotus Development Corporation)" <Noah_Mendelsohn@lotus.com>, "David C. Fallside (IBM)" fallside@us.ibm.com

The following comments are (mainly) editorial comments by Joseph Reagle on the XML Schema last call Working Draft [1]. 

[1] http://www.w3.org/TR/2000/WD-xmlschema-0-20000407/

Glossary; and Model Groups, Model Group Definitions, and Element Declarations
I find the distinction between these things confusing, perhaps it could be simplified or more text could be spent on describing how these things are different. Actually, I look forward to the glossary being completed as this will help me in understanding the specification. See [2] for more:
[2] http://lists.w3.org/Archives/Public/xmlschema-dev/2000Apr/0021.html
2.2 XML Schema Abstract Data Model
I could understand this chapter better if the 12 components listed somehow corresponded more closely to the 2.2.* section headings. Perhaps, a quick definition on each of the 12 components, or a move away from the "primary" and "secondary" and "helper" designations (towards others) if those terms aren't substantively used elsewhere.
2.5 Names and Symbol Spaces     
The fact that you are using the same namespace "http://www.w3.org/1999/XMLSchema" across different specifications with substantively different syntaxes may cause problems for applications that expect the definition of a dated name space to be stable. See [3] for more discussion on this topic:
[3] http://lists.w3.org/Archives/Public/xmlschema-dev/2000Apr/0026.html
Namespace Prefixes
When trying to understand the specifications, I frequently found myself bouncing between the primer, structures, and datatypes documents, frequently using find or grep facilities to find bits of examples. Using a consistent namespace prefix (xs: or xsd:) through all documents would be helpful.
2.6 Schema-Related Markup in Documents Being Schema-Validated
Could the Schema Instance namespace somehow relate to the Schema namespace? For instance, I'd find it easier to understand who defined the schema instance namespace with something like: http://www.w3.org/1999/XMLSchema/Instance
Appendix A (normative) Schema for Schemas
It would be useful for XML declarations to include more explicit declarations of DTD and schema locations. For instance:
<xml version='1.0'?>
<!-- XML Schema schema for XML Schemas: Part 1: Structures -->
<!DOCTYPE schema PUBLIC "-//W3C//DTD XMLSCHEMA 19991216//EN" 

<schema xmlns="http://www.w3.org/1999/XMLSchema" 
 blockDefault="#all" elementFormDefault="qualified" 
 version="Id: XMLSchema.xsd,v 1.1 2000/04/06 13:51:05 aqw Exp"
 xsi:schemaLocation ="http://www.w3.org/1999/XMLSchema.xsd" >
The more explicit representation of default values in schema component definitions is useful. However, the many varied defaults can still be confusing, perhaps this could be simplified, or a table could be provided that includes all default values.
3. Advanced Concepts I: Namespaces, Schemas & Qualification
This topic (not necessarily the exposition) is difficult to comprehend with respect to both comprehending the concepts and as a potential source of validation errors in instances I create. Perhaps some guidelines such as, "If you want to create an instance that has no prefixes in children elements then X; if you want to create an instance ... Y" so readers can easily jump-start their own schema writing.