spv-file-format: Improve documentation.

[pspp] / doc / dev / spv-file-format.texi

diff --git a/doc/dev/spv-file-format.texi b/doc/dev/spv-file-format.texi
index 34b0ac585c4bfae7477bc5bf0cdd5c7a4675ac57..9c431e459bd16ad64cd89f3be717c8d9e5eb7248 100644 (file)
--- a/doc/dev/spv-file-format.texi
+++ b/doc/dev/spv-file-format.texi
@@ -29,7 +29,9 @@ Java ``JAR'' files (and ODF files), but whereas a JAR manifest
 contains a sequence of colon-delimited key/value pairs, an SPV
 manifest contains the string @samp{allowPivoting=true}, without a
 new-line.  PSPP uses this string to identify an SPV file; it is
-invariant across the corpus.
+invariant across the corpus.@footnote{SPV files always begin with the
+7-byte sequence 50 4b 03 04 14 00 08, but this is not a useful magic
+number because most Zip archives start the same way.}
 
 The rest of the members in an SPV file's Zip archive fall into two
 categories: @dfn{structure} and @dfn{detail} members.  Structure
@@ -343,8 +345,8 @@ December 5, 2014 5:00:19 o'clock PM EST}.
 
 @defvr {Attribute} @code{lockReader}
 Whether a reader should be allowed to edit the output.  The possible
-values are @code{true} and @code{false}, but the corpus only contains
-@code{false}.
+values are @code{true} and @code{false}.  The value @code{false} is by
+far the most common.
 @end defvr
 
 @defvr {Attribute} @code{schemaLocation}
@@ -1969,8 +1971,10 @@ An XML Schema for VizML is available, distributed with SPSS binaries,
 under a nonfree license.  It contains documentation that is
 occasionally helpful.
 
-See @file{src/output/spv/detail-xml.grammar} in the PSPP source tree
-for the full grammar that it uses for parsing.
+This section describes the detail XML format using the same notation
+already used for the structure XML format (@pxref{SPV Structure Member
+Format}).  See @file{src/output/spv/detail-xml.grammar} in the PSPP
+source tree for the full grammar that it uses for parsing.
 
 The important elements of the detail XML format are: