UPDATE: Dump of initial files

xlsx/documentation/README.md

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+Documentation
+=============
+
+An `xlsx` is a zip file containing a set of folders and `xml` files. The IronCalc json structure mimics the relevant parts of the Excel zip.
+Although the xlsx structure is quite complicated, it's essentials regarding the spreadsheet technology are easier to grasp.
+
+The simplest workbook folder structure might look like this:
+
+```
+docProps
+    app.xml
+    core.xml
+
+_rels
+    .rels
+
+xl
+    _rels
+        workbook.xml.rels
+    theme
+        theme1.xml
+    worksheets
+        sheet1.xml
+    calcChain.xml
+    styles.xml
+    workbook.xml
+    sharedStrings.xml
+
+[Content_Types].xml
+```
+
+Note that more complicated workbooks will have many more files and folders.
+For instance charts, pivot tables, comments, tables,...
+
+The relevant json structure in IronCalc will be:
+
+
+```json
+{
+    "name": "Workbook1",
+    "defined_names": [],
+    "shared_strings": [],
+    "worksheets": [],
+    "styles": {
+        "num_fmts": [],
+        "fonts": [],
+        "fills": [],
+        "borders": [],
+        "cell_style_xfs": [],
+        "cell_styles" : [],
+        "cell_xfs": []
+    }
+}
+```
+
+Note that there is not a 1-1 correspondence but there is a close resemblance.
+
+
+
+SpreadsheetML
+-------------
+International standard (Four edition 2016-11-01): ECMA-376, ISO/IEC 29500-1
+* [iso](https://standards.iso.org/ittf/PubliclyAvailableStandards/c071691_ISO_IEC_29500-1_2016.zip)
+* [ecma](http://www.ecma-international.org/publications/standards/Ecma-376.htm)