Office Binary (doc, xls, ppt) Translator to Open XML
Table of Contents
- High-Level Architecture Description
- How to Retrieve Text from a Binary .doc File
- Mapping Tables
- File Format Documentation
High-Level Architecture Description
Structured storage (also known as compound file) is a technology to store hierarchical data within a single file. Microsoft Office uses the structured storage as a container for storing binary Office documents (doc, xls, ppt).
Such a structured storage container is made up of a number of virtual streams which contain text, data and control structures of the binary Office documents, i.e. the container is like a small file system of its own. The content of these streams or subfiles is document type-specific, i.e. Word documents contain other streams than Excel spreadsheets or PowerPoint presentations.
Consequently, we have to tackle two levels of format interpretation:
- understanding the structured storage format and extracting the individual streams
- interpreting the document type-specific streams and building an internal data structure
Subsequently, these internal data structures will then be translated to equivalent Open XML element structures using mapping tables (these mapping tables are also document type-specific; a very initial version of a doc to docx mapping table can be found here).
In a last step, the Open XML element structures are assembled into an Open XML package file.
The diagram below shows a high-level view of the planned architecture of the Office Binary (doc, xls, ppt) Translator to Open XML project (Note: Since all the binary Office formats use the same approach for storing meta data, the Property Reader & Generator component can be used for all document types).
We will focus in the first phase of this project on the translation of binary Word documents to Open XML Word documents (doc to docx).
Streams in a Word Document
A binary Word file (doc) consists of the following streams inside the structured storage:
- main stream (WordDocument)
- summary information stream (the summary information for a Word document is actually stored in two structured storage streams,
- SummaryInformation and DocumentSummaryInformation)
- table stream (0Table or 1Table)
- data stream (optional, Data)
- custom XML storage (optional, added in Word 2007)
- 0 or more object streams which contain private data for embedded objects within the Word document
The diagram below shows the streams in a sample Word document
More details will follow in the weeks to come.
How to Retrieve Text from a Binary .doc File
It's a bit tricky to extract the text contained in a binary Word document; however, we've managed it. Have a look here about more details.
A Guide to Table Formatting
Table formatting is another demanding conversion task. Some details can be found here.
Mapping Tables
- Updated draft (v0.02) mapping table for binary Word (doc) to Open XML (docx) documents (table in XLSX Format or PDF Format)
File Format Documentation