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+<title>Principles Of Operation</title>
+
+This page attempts to define the foundational principles upon
+which Fossil is built.
+
+  *  A project consists of source files, wiki pages, and
+     trouble tickets, and control files (collectively "artifacts").
+     All historical copies of all artifacts
+     are saved.  The project maintains an audit
+     trail.
+     
+  *  A project resides in one or more repositories.  Each
+     repository is administered and operates independently
+     of the others.
+     
+  *  Each repository has both global and local state.  The
+     global state is common to all repositories (or at least
+     has the potential to be shared in common when the
+     repositories are fully synchronized).  The local state
+     for each repository is private to that repository.
+     The global state represents the content of the project.
+     The local state identifies the authorized users and
+     access policies for a particular repository.
+     
+  *  The global state of a repository is an unordered
+     collection of artifacts.  Each artifact is named by a
+     cryptographic hash (SHA1 or SHA3-256) encoded in
+     lowercase hexadecimal.
+     In many contexts, the name can be
+     abbreviated to a unique prefix.  A five- or six-character
+     prefix usually suffices to uniquely identify a file.
+     
+  *  Because artifacts are named by a cryptographic hash, all artifacts
+     are immutable.  Any change to the content of an artifact also
+     changes the hash that forms the artifacts name, thus
+     creating a new artifact.  Both the old original version of the
+     artifact and the new change are preserved under different names.
+     
+  *  It is theoretically possible for two artifacts with different
+     content to share the same hash.  But finding two such
+     artifacts is so incredibly difficult and unlikely that we
+     consider it to be an impossibility.
+     
+  *  The signature of an artifact is the cryptographic hash of the
+     artifact itself, exactly as it would appear in a disk file.  No prefix
+     or meta-information about the artifact is added before computing
+     the hash.  So you can
+     always find the signature of a file by using the
+     "sha1sum" or "sha3sum" or similar command-line utilities.
+     
+  *  The artifacts that comprise the global state of a repository
+     are the complete global state of that repository.  The SQLite
+     database that holds the repository contains additional information
+     about linkages between artifacts, but all of that added information
+     can be discarded and reconstructed by rescanning the content
+     artifacts.
+     
+  *  Two repositories for the same project can synchronize
+     their global states simply by sharing artifacts.  The local
+     state of repositories is not normally synchronized or
+     shared.
+     
+  *  Every check-in has a special file at the top-level
+     named "manifest" which is an index of all other files in
+     that check-in.  The manifest is automatically created and
+     maintained by the system.
+     
+  *  The <a href="fileformat.wiki">file formats</a>
+     used by Fossil are all very simple so that with access
+     to the original content files, one can easily reconstruct
+     the content of a check-in without the need for any
+     special tools or software.