WIP

crates/crdb/src/README.md

@@ -1,18 +1,47 @@
-A conflict-free replicated database.
+# CRDB: A conflict-free replicated database for code and markdown
 
 Our goal is for this database to contain all the text inserted in Zed.
 
+## Contexts
+
 The database is divided into *contexts*, with each context containing a collection of *documents*.
 
+### Contexts contain documents
+
 These contexts and the documents are really just namespaces in a global table of document *fragments*. Each fragment is a sequence of one or more characters, which may or may not be visible in a given branch.
 
-There are two different kinds of contexts:
+#### Documents with paths are files
+
+Documents in a context can be associated with metadata. If a document is associated with a relative path, it represents a file. A context that contains files can be synchronized with a directory tree on the file system, much like a Git repository.
+
+#### Conversations are also documents
+
+Contexts can also be associated with conversations, which are special documents that embed other documents that represent messages. Messages are embedded via a mechanism called *transclusion*, which will be discussed further below.
+
+### Contexts occupy a hierarchical namespace
+
+For example, at genesis, zed.dev will contain the following channels:
+
+#zed
+    - This is where people get oriented about what Zed is all about. We'll link to it from our landing page.
+#zed/staff
+    - Here's where we talk about stuff private to the company, and host company-specific files.
+#zed/insiders
+    - Users we've worked with.
+#zed/zed
+    - This contains the actual source code for Zed.
 
-Worktrees: A worktree is assumed to contain many documents with paths relative to some shared root. Worktrees can be used to collaborate on source code, but also documentation in a variety of formats, such as markdown, or other page generation formats.
 
-Channels: Worktrees are associated with one or more channels, and channels are associated with zero or more worktrees. Channels are named by paths in a hierarchical namespace.
 
-The channel namespace is also the top-level namespace for zed.dev URLs.
 
 https://zed.dev/zed -> The #zed channel.
 https://zed.dev/zed/insiders -> The #zed/insiders channel.
+
+
+## Versions
+
+Our current buffer CRDT represents versions with version vectors. Every collaborator is assigned a unique replica id, and for each collaborator that has ever participated, there is an entry in the version vector mapping their replica id to an operation count.
+
+With CRDB, our goal is to expand from an individual buffer to collections of multiple documents called *contexts*. Each context allows an arbitrary number of branches to be created, and each branch can be edited independently from other branches, with synchronization between branches performed at a time of the user's choosing, much like Git.
+
+This raises some concerns about using vectors to represent versions, as the size of the vectors will grow linearly in the number of branches, even if portions of the vectors