--- a/bitten/build/api.py
+++ b/bitten/build/api.py
@@ -7,6 +7,8 @@
 # you should have received as part of this distribution. The terms
 # are also available at http://bitten.cmlenz.net/wiki/License.
 
+"""Functions and classes used to simplify the implementation recipe commands."""
+
 import logging
 import fnmatch
 import os
@@ -43,17 +45,16 @@
 
 class CommandLine(object):
     """Simple helper for executing subprocesses."""
-    # TODO: Use 'subprocess' module if available (Python >= 2.4)
 
     def __init__(self, executable, args, input=None, cwd=None):
         """Initialize the CommandLine object.
         
-        @param executable The name of the program to execute
-        @param args A list of arguments to pass to the executable
-        @param input String or file-like object containing any input data for
-                     the program
-        @param cwd The working directory to change to before executing the
-                   command
+        @param executable: the name of the program to execute
+        @param args: a list of arguments to pass to the executable
+        @param input: string or file-like object containing any input data for
+            the program
+        @param cwd: The working directory to change to before executing the
+            command
         """
         self.executable = executable
         self.arguments = [str(arg) for arg in args]
@@ -66,6 +67,12 @@
     if os.name == 'nt': # windows
 
         def execute(self, timeout=None):
+            """Execute the command, and return a generator for iterating over
+            the output written to the standard output and error streams.
+            
+            @param timeout: number of seconds before the external process
+                should be aborted (not supported on Windows)
+            """
             args = [self.executable] + self.arguments
             for idx, arg in enumerate(args):
                 if arg.find(' ') >= 0:
@@ -126,6 +133,12 @@
     else: # posix
 
         def execute(self, timeout=None):
+            """Execute the command, and return a generator for iterating over
+            the output written to the standard output and error streams.
+            
+            @param timeout: number of seconds before the external process
+                should be aborted (not supported on Windows)
+            """
             import popen2, select
             if self.cwd:
                 old_cwd = os.getcwd()
@@ -215,6 +228,14 @@
                         '.DS_Store', 'Thumbs.db']
 
     def __init__(self, basedir, include=None, exclude=None):
+        """Create the file set.
+        
+        @param basedir: the base directory for all files in the set
+        @param include: a list of patterns that define which files should be
+            included in the set
+        @param exclude: a list of patterns that define which files should be
+            excluded from the set
+        """
         self.files = []
         self.basedir = basedir
 
@@ -254,8 +275,13 @@
                     self.files.append(filepath)
 
     def __iter__(self):
+        """Iterate over the names of all files in the set."""
         for filename in self.files:
             yield filename
 
     def __contains__(self, filename):
+        """Return whether the given file name is in the set.
+        
+        @param filename: the name of the file to check
+        """
         return filename in self.files

--- a/bitten/build/config.py
+++ b/bitten/build/config.py
@@ -7,6 +7,8 @@
 # you should have received as part of this distribution. The terms
 # are also available at http://bitten.cmlenz.net/wiki/License.
 
+"""Support for build slave configuration."""
+
 from ConfigParser import SafeConfigParser
 import logging
 import os
@@ -88,12 +90,23 @@
                     self.packages[package][propname] = value
 
     def __contains__(self, key):
+        """Return whether the configuration contains a value for the specified
+        key.
+        
+        @param key: name of the configuration option using dotted notation
+            (for example, "python.path")
+        """
         if '.' in key:
             package, propname = key.split('.', 1)
             return propname in self.packages.get(package, {})
         return key in self.properties
 
     def __getitem__(self, key):
+        """Return the value for the specified configuration key.
+        
+        @param key: name of the configuration option using dotted notation
+            (for example, "python.path")
+        """
         if '.' in key:
             package, propname = key.split('.', 1)
             return self.packages.get(package, {}).get(propname)
@@ -102,9 +115,15 @@
     def __str__(self):
         return str({'properties': self.properties, 'packages': self.packages})
 
-    _VAR_RE = re.compile(r'\$\{(?P<ref>\w[\w.]*?\w)(?:\:(?P<def>.+))?\}')
+    def get_dirpath(self, key):
+        """Return the value of the specified configuration key, but verify that
+        the value refers to the path of an existing directory.
+        
+        If the value does not exist, or is not a directory path, return C{None}.
 
-    def get_dirpath(self, key):
+        @param key: name of the configuration option using dotted notation
+            (for example, "ant.home")
+        """
         dirpath = self[key]
         if dirpath:
             if os.path.isdir(dirpath):
@@ -113,6 +132,14 @@
         return None
 
     def get_filepath(self, key):
+        """Return the value of the specified configuration key, but verify that
+        the value refers to the path of an existing file.
+        
+        If the value does not exist, or is not a file path, return C{None}.
+
+        @param key: name of the configuration option using dotted notation
+            (for example, "python.path")
+        """
         filepath = self[key]
         if filepath:
             if os.path.isfile(filepath):
@@ -120,15 +147,19 @@
             log.warning('Invalid %s: %s is not a file', key, filepath)
         return None
 
+    _VAR_RE = re.compile(r'\$\{(?P<ref>\w[\w.]*?\w)(?:\:(?P<def>.+))?\}')
+
     def interpolate(self, text):
         """Interpolate configuration properties into a string.
         
         Properties can be referenced in the text using the notation
-        `${property.name}`. A default value can be provided by appending it to
+        C{${property.name}}. A default value can be provided by appending it to
         the property name separated by a colon, for example
-        `${property.name:defaultvalue}`. This value will be used when there's
+        C{${property.name:defaultvalue}}. This value will be used when there's
         no such property in the configuration. Otherwise, if no default is
         provided, the reference is not replaced at all.
+
+        @param text: the string containing variable references
         """
         def _replace(m):
             refname = m.group('ref')

--- a/bitten/build/ctools.py
+++ b/bitten/build/ctools.py
@@ -7,6 +7,8 @@
 # you should have received as part of this distribution. The terms
 # are also available at http://bitten.cmlenz.net/wiki/License.
 
+"""Recipe commands for build tasks commonly used for C/C++ projects."""
+
 import logging
 import re
 import os
@@ -22,7 +24,18 @@
 
 def configure(ctxt, file_='configure', enable=None, disable=None, with=None,
               without=None, cflags=None, cxxflags=None):
-    """Run a configure script."""
+    """Run a C{configure} script.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param file_: name of the configure script
+    @param enable: names of the features to enable, seperated by spaces
+    @param disable: names of the features to disable, separated by spaces
+    @param with: names of external packages to include
+    @param without: names of external packages to exclude
+    @param cflags: C{CFLAGS} to pass to the configure script
+    @param cxxflags: C{CXXFLAGS} to pass to the configure script
+    """
     args = []
     if enable:
         args += ['--enable-%s' % feature for feature in enable.split()]
@@ -48,7 +61,14 @@
         ctxt.error('configure failed (%s)' % returncode)
 
 def make(ctxt, target=None, file_=None, keep_going=False):
-    """Execute a Makefile target."""
+    """Execute a Makefile target.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param file_: name of the Makefile
+    @param keep_going: whether make should keep going when errors are
+        encountered
+    """
     executable = ctxt.config.get_filepath('make.path') or 'make'
 
     args = ['--directory', ctxt.basedir]
@@ -65,7 +85,15 @@
         ctxt.error('make failed (%s)' % returncode)
 
 def cppunit(ctxt, file_=None, srcdir=None):
-    """Collect CppUnit XML data."""
+    """Collect CppUnit XML data.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param file_: path of the file containing the CppUnit results; may contain
+        globbing wildcards to match multiple files
+    @param srcdir: name of the directory containing the source files, used to
+        link the test results to the corresponding files
+    """
     assert file_, 'Missing required attribute "file"'
 
     try:
@@ -126,7 +154,15 @@
         log.warning('Error parsing CppUnit results file (%s)', e)
 
 def gcov(ctxt, include=None, exclude=None, prefix=None):
-    """Run `gcov` to extract coverage data where available."""
+    """Run C{gcov} to extract coverage data where available.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param include: patterns of files and directories to include
+    @param exclude: patterns of files and directories that should be excluded
+    @param prefix: optional prefix name that is added to object files by the
+        build system
+    """
     file_re = re.compile(r'^File \`(?P<file>[^\']+)\'\s*$')
     lines_re = re.compile(r'^Lines executed:(?P<cov>\d+\.\d+)\% of (?P<num>\d+)\s*$')
 

--- a/bitten/build/javatools.py
+++ b/bitten/build/javatools.py
@@ -7,6 +7,8 @@
 # you should have received as part of this distribution. The terms
 # are also available at http://bitten.cmlenz.net/wiki/License.
 
+"""Recipe commands for tools commonly used in Java projects."""
+
 from glob import glob
 import logging
 import os
@@ -20,7 +22,15 @@
 log = logging.getLogger('bitten.build.javatools')
 
 def ant(ctxt, file_=None, target=None, keep_going=False, args=None):
-    """Run an Ant build."""
+    """Run an Ant build.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param file_: name of the Ant build file
+    @param target: name of the target that should be executed (optional)
+    @param keep_going: whether Ant should keep going when errors are encountered
+    @param args: additional arguments to pass to Ant
+    """
     executable = 'ant'
     ant_home = ctxt.config.get_dirpath('ant.home')
     if ant_home:
@@ -83,7 +93,15 @@
         ctxt.error('Ant failed (%s)' % cmdline.returncode)
 
 def junit(ctxt, file_=None, srcdir=None):
-    """Extract test results from a JUnit XML report."""
+    """Extract test results from a JUnit XML report.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param file_: path to the JUnit XML test results; may contain globbing
+        wildcards for matching multiple results files
+    @param srcdir: name of the directory containing the test sources, used to
+        link test results to the corresponding source files
+    """
     assert file_, 'Missing required attribute "file"'
     try:
         total, failed = 0, 0

--- a/bitten/build/pythontools.py
+++ b/bitten/build/pythontools.py
@@ -7,6 +7,8 @@
 # you should have received as part of this distribution. The terms
 # are also available at http://bitten.cmlenz.net/wiki/License.
 
+"""Recipe commands for tools commonly used by Python projects."""
+
 import logging
 import os
 import re
@@ -33,8 +35,14 @@
         return python_path
     return sys.executable
 
-def distutils(ctxt, command='build', file_='setup.py'):
-    """Execute a `distutils` command."""
+def distutils(ctxt, file_='setup.py', command='build'):
+    """Execute a C{distutils} command.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param file_: name of the file defining the distutils setup
+    @param command: the setup command to execute
+    """
     cmdline = CommandLine(_python_path(ctxt), [ctxt.resolve(file_), command],
                           cwd=ctxt.basedir)
     log_elem = xmlio.Fragment()
@@ -61,7 +69,21 @@
         ctxt.error('distutils failed (%s)' % cmdline.returncode)
 
 def exec_(ctxt, file_=None, module=None, function=None, output=None, args=None):
-    """Execute a python script."""
+    """Execute a Python script.
+    
+    Either the C{file_} or the C{module} parameter must be provided. If
+    specified using the C{file_} parameter, the file must be inside the project
+    directory. If specified as a module, the module must either be resolvable
+    to a file, or the C{function} parameter must be provided
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param file_: name of the script file to execute
+    @param module: name of the Python module to execute
+    @param function: name of the Python function to run
+    @param output: name of the file to which output should be written
+    @param args: extra arguments to pass to the script
+    """
     assert file_ or module, 'Either "file" or "module" attribute required'
     if function:
         assert module and not file_, '"module" attribute required for use of ' \
@@ -89,7 +111,12 @@
                     output=output, args=args)
 
 def pylint(ctxt, file_=None):
-    """Extract data from a `pylint` run written to a file."""
+    """Extract data from a C{pylint} run written to a file.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param file_: name of the file containing the Pylint output
+    """
     assert file_, 'Missing required attribute "file"'
     msg_re = re.compile(r'^(?P<file>.+):(?P<line>\d+): '
                         r'\[(?P<type>[A-Z]\d*)(?:, (?P<tag>[\w\.]+))?\] '
@@ -125,7 +152,16 @@
         log.warning('Error opening pylint results file (%s)', e)
 
 def trace(ctxt, summary=None, coverdir=None, include=None, exclude=None):
-    """Extract data from a `trace.py` run."""
+    """Extract data from a C{trace.py} run.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param summary: path to the file containing the coverage summary
+    @param coverdir: name of the directory containing the per-module coverage
+        details
+    @param include: patterns of files or directories to include in the report
+    @param exclude: patterns of files or directories to exclude from the report
+    """
     assert summary, 'Missing required attribute "summary"'
     assert coverdir, 'Missing required attribute "coverdir"'
 
@@ -246,7 +282,12 @@
         log.warning('Error opening coverage summary file (%s)', e)
 
 def unittest(ctxt, file_=None):
-    """Extract data from a unittest results file in XML format."""
+    """Extract data from a unittest results file in XML format.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param file_: name of the file containing the test results
+    """
     assert file_, 'Missing required attribute "file"'
 
     try:

--- a/bitten/build/shtools.py
+++ b/bitten/build/shtools.py
@@ -7,6 +7,8 @@
 # you should have received as part of this distribution. The terms
 # are also available at http://bitten.cmlenz.net/wiki/License.
 
+"""Generic recipe commands for executing external processes."""
+
 import logging
 import os
 import shlex
@@ -17,7 +19,17 @@
 log = logging.getLogger('bitten.build.shtools')
 
 def exec_(ctxt, executable=None, file_=None, output=None, args=None):
-    """Execute a shell script."""
+    """Execute a program or shell script.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param executable: name of the executable to run
+    @param file_: name of the script file, relative to the project directory,
+        that should be run
+    @param output: name of the file to which the output of the script should be
+        written
+    @param args: command-line arguments to pass to the script
+    """
     assert executable or file_, \
         'Either "executable" or "file" attribute required'
 
@@ -29,7 +41,19 @@
 
 def pipe(ctxt, executable=None, file_=None, input_=None, output=None,
          args=None):
-    """Pipe the contents of a file through a script."""
+    """Pipe the contents of a file through a program or shell script.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param executable: name of the executable to run
+    @param file_: name of the script file, relative to the project directory,
+        that should be run
+    @param input_: name of the file containing the data that should be passed
+        to the shell script on its standard input stream
+    @param output: name of the file to which the output of the script should be
+        written
+    @param args: command-line arguments to pass to the script
+    """
     assert executable or file_, \
         'Either "executable" or "file" attribute required'
     assert input_, 'Missing required attribute "input"'
@@ -42,7 +66,22 @@
 
 def execute(ctxt, executable=None, file_=None, input_=None, output=None,
             args=None):
-    """Generic external program execution."""
+    """Generic external program execution.
+    
+    This function is not itself bound to a recipe command, but rather used from
+    other commands.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param executable: name of the executable to run
+    @param file_: name of the script file, relative to the project directory,
+        that should be run
+    @param input_: name of the file containing the data that should be passed
+        to the shell script on its standard input stream
+    @param output: name of the file to which the output of the script should be
+        written
+    @param args: command-line arguments to pass to the script
+    """
     if args:
         if isinstance(args, basestring):
             args = shlex.split(args)

--- a/bitten/build/xmltools.py
+++ b/bitten/build/xmltools.py
@@ -7,6 +7,8 @@
 # you should have received as part of this distribution. The terms
 # are also available at http://bitten.cmlenz.net/wiki/License.
 
+"""Recipe commands for XML processing."""
+
 import logging
 import os
 
@@ -32,7 +34,17 @@
 log = logging.getLogger('bitten.build.xmltools')
 
 def transform(ctxt, src=None, dest=None, stylesheet=None):
-    """Apply an XSLT stylesheet to a source XML document."""
+    """Apply an XSLT stylesheet to a source XML document.
+    
+    This command requires either libxslt (with Python bindings), or MSXML to
+    be installed.
+    
+    @param ctxt: the build context
+    @type ctxt: an instance of L{bitten.recipe.Context}
+    @param src: name of the XML input file
+    @param dest: name of the XML output file
+    @param stylesheet: name of the file containing the XSLT stylesheet
+    """
     assert src, 'Missing required attribute "src"'
     assert dest, 'Missing required attribute "dest"'
     assert stylesheet, 'Missing required attribute "stylesheet"'

--- a/bitten/master.py
+++ b/bitten/master.py
@@ -7,6 +7,13 @@
 # you should have received as part of this distribution. The terms
 # are also available at http://bitten.cmlenz.net/wiki/License.
 
+"""Build master implementation.
+
+This module is runnable as a script to launch the build master. The build
+master starts a single process that handles connections to any number of build
+slaves.
+"""
+
 import calendar
 from datetime import datetime, timedelta
 import logging
@@ -30,6 +37,7 @@
 
 
 class Master(beep.Listener):
+    """BEEP listener implementation for the build master."""
 
     def __init__(self, envs, ip, port, adjust_timestamps=False,
                  check_interval=DEFAULT_CHECK_INTERVAL):
@@ -104,6 +112,8 @@
 class OrchestrationProfileHandler(beep.ProfileHandler):
     """Handler for communication on the Bitten build orchestration profile from
     the perspective of the build master.
+
+    An instance of this class is associated with exactly one remote build slave.
     """
     URI = 'http://bitten.cmlenz.net/beep/orchestration'
 
@@ -352,6 +362,7 @@
         raise ValueError, 'Invalid ISO date/time %s (%s)' % (string, e)
 
 def main():
+    """Main entry point for running the build master."""
     from bitten import __version__ as VERSION
     from optparse import OptionParser
 

--- a/bitten/queue.py
+++ b/bitten/queue.py
@@ -7,6 +7,17 @@
 # you should have received as part of this distribution. The terms
 # are also available at http://bitten.cmlenz.net/wiki/License.
 
+"""Implements the scheduling of builds for a project.
+
+This module provides the functionality for scheduling builds for a specific
+Trac environment. It is used by both the build master and the web interface to
+get the list of required builds (revisions not built yet).
+
+Furthermore, the C{BuildQueue} class is used by the build master to determine
+the next pending build, and to match build slaves against configured target
+platforms.
+"""
+
 from itertools import ifilter
 import logging
 import re
@@ -24,6 +35,10 @@
     This function is a generator that yields `(platform, rev, build)` tuples,
     where `platform` is a `TargetPlatform` object, `rev` is the identifier of
     the changeset, and `build` is a `Build` object or `None`.
+
+    @param repos: The version control repository
+    @param config: The build configuration
+    @param db: a database connection (optional)
     """
     env = config.env
     if not db:
@@ -98,7 +113,7 @@
         where `build` is the `Build` object and `slave` is the name of the
         build slave.
 
-        Otherwise, this function will return `(None, None)`.
+        Otherwise, this function will return C{(None, None)}
         """
         log.debug('Checking for pending builds...')
 
@@ -155,7 +170,7 @@
             repos.close()
 
     def reset_orphaned_builds(self):
-        """Reset all in-progress builds to `PENDING` state.
+        """Reset all in-progress builds to PENDING state.
         
         This is used to cleanup after a crash of the build master process,
         which would leave in-progress builds in the database that aren't
@@ -177,13 +192,13 @@
     def register_slave(self, name, properties):
         """Register a build slave with the queue.
         
-        @param name: The name of the slave
-        @param properties: A `dict` containing the properties of the slave
-        @return: whether the registration was successful
-
         This method tries to match the slave against the configured target
         platforms. Only if it matches at least one platform will the
         registration be successful.
+        
+        @param name: The name of the slave
+        @param properties: A dict containing the properties of the slave
+        @return: Whether the registration was successful
         """
         any_match = False
         for config in BuildConfig.select(self.env):
@@ -212,12 +227,12 @@
     def unregister_slave(self, name):
         """Unregister a build slave.
         
-        @param name: The name of the slave
-        @return: `True` if the slave was registered for this build queue,
-                 `False` otherwise
-
         This method removes the slave from the registry, and also resets any
         in-progress builds by this slave to `PENDING` state.
+        
+        @param name: The name of the slave
+        @return: C{True} if the slave was registered for this build queue,
+            C{False} otherwise
         """
         for slaves in self.slaves.values():
             if name in slaves:

--- a/bitten/recipe.py
+++ b/bitten/recipe.py
@@ -7,6 +7,12 @@
 # you should have received as part of this distribution. The terms
 # are also available at http://bitten.cmlenz.net/wiki/License.
 
+"""Execution of build recipes.
+
+This module provides various classes that can be used to process build recipes,
+most importantly the L{Recipe} class.
+"""
+
 import keyword
 import logging
 import os
@@ -20,27 +26,41 @@
 from bitten.build.config import Configuration
 from bitten.util import xmlio
 
-__all__ = ['Recipe']
+__all__ = ['Recipe', 'InvalidRecipeError']
 
 log = logging.getLogger('bitten.recipe')
 
 
 class InvalidRecipeError(Exception):
-    """Exception raised when a recipe cannot be processed."""
+    """Exception raised when a recipe is not valid."""
 
 
 class Context(object):
-    """The context in which a recipe command or report is run."""
+    """The context in which a build is executed."""
 
     step = None # The current step
     generator = None # The current generator (namespace#name)
 
     def __init__(self, basedir, config=None):
+        """Initialize the context.
+        
+        @param basedir: a string containing the working directory for the build
+        @param config: the build slave configuration
+        @type config: an instance of L{bitten.build.config.Configuration}
+        """
         self.basedir = os.path.realpath(basedir)
         self.config = config or Configuration()
         self.output = []
 
     def run(self, step, namespace, name, attr):
+        """Run the specified recipe command.
+        
+        @param step: the build step that the command belongs to
+        @param namespace: the namespace URI of the command
+        @param name: the local tag name of the command
+        @param attr: a dictionary containing the attributes defined on the
+            command element
+        """
         self.step = step
 
         try:
@@ -73,15 +93,34 @@
             self.step = None
 
     def error(self, message):
+        """Record an error message.
+        
+        @param message: A string containing the error message.
+        """
         self.output.append((Recipe.ERROR, None, self.generator, message))
 
-    def log(self, xml_elem):
-        self.output.append((Recipe.LOG, None, self.generator, xml_elem))
+    def log(self, xml):
+        """Record log output.
+        
+        @param xml: an XML fragment containing the log messages
+        """
+        self.output.append((Recipe.LOG, None, self.generator, xml))
 
-    def report(self, category, xml_elem):
-        self.output.append((Recipe.REPORT, category, self.generator, xml_elem))
+    def report(self, category, xml):
+        """Record report data.
+        
+        @param category: the name of category of the report
+        @param xml: an XML fragment containing the report data
+        """
+        self.output.append((Recipe.REPORT, category, self.generator, xml))
 
     def report_file(self, category=None, file_=None):
+        """Read report data from a file and record it.
+        
+        @param category: the name of the category of the report
+        @param file_: the path to the file containing the report data, relative
+            to the base directory
+        """
         try:
             fileobj = file(self.resolve(file_), 'r')
             try:
@@ -102,6 +141,11 @@
                        % (category, filename, e))
 
     def resolve(self, *path):
+        """Return the path of a file relative to the base directory.
+        
+        Accepts any number of positional arguments, which are joined using the
+        system path separator to form the path.
+        """
         return os.path.normpath(os.path.join(self.basedir, *path))
 
 
@@ -113,12 +157,22 @@
     """
 
     def __init__(self, elem):
+        """Create the step.
+        
+        @param elem: the XML element representing the step
+        @type elem: an instance of L{bitten.util.xmlio.ParsedElement}
+        """
         self._elem = elem
         self.id = elem.attr['id']
         self.description = elem.attr.get('description')
         self.onerror = elem.attr.get('onerror', 'fail')
 
     def execute(self, ctxt):
+        """Execute this step in the given context.
+        
+        @param ctxt: the build context
+        @type ctxt: an instance of L{Context}
+        """
         for child in self._elem:
             ctxt.run(self, child.namespace, child.name, child.attr)
 
@@ -138,8 +192,8 @@
 class Recipe(object):
     """A build recipe.
     
-    Iterate over this object to get the individual build steps in the order they
-    have been defined in the recipe file.
+    Iterate over this object to get the individual build steps in the order
+    they have been defined in the recipe file.
     """
 
     ERROR = 'error'
@@ -147,16 +201,38 @@
     REPORT = 'report'
 
     def __init__(self, xml, basedir=os.getcwd(), config=None):
+        """Create the recipe.
+        
+        @param xml: the XML document representing the recipe
+        @type xml: an instance of L{bitten.util.xmlio.ParsedElement}
+        @param basedir: the base directory for the build
+        @param config: the slave configuration (optional)
+        @type config: an instance of L{bitten.build.config.Configuration}
+        """
         assert isinstance(xml, xmlio.ParsedElement)
         self.ctxt = Context(basedir, config)
         self._root = xml
 
     def __iter__(self):
-        """Provide an iterator over the individual steps of the recipe."""
+        """Iterate over the individual steps of the recipe."""
         for child in self._root.children('step'):
             yield Step(child)
 
     def validate(self):
+        """Validate the recipe.
+        
+        This method checks a number of constraints:
+         - the name of the root element must be "build"
+         - the only permitted child elements or the root element with the name
+           "step"
+         - the recipe must contain at least one step
+         - step elements must have a unique "id" attribute
+         - a step must contain at least one nested command
+         - commands must not have nested content
+
+        @raise InvalidRecipeError: in case any of the above contraints is
+            violated
+        """
         if self._root.name != 'build':
             raise InvalidRecipeError, 'Root element must be <build>'
         steps = list(self._root.children())

--- a/bitten/slave.py
+++ b/bitten/slave.py
@@ -7,6 +7,8 @@
 # you should have received as part of this distribution. The terms
 # are also available at http://bitten.cmlenz.net/wiki/License.
 
+"""Implementation of the build slave."""
+
 from datetime import datetime
 import logging
 import os
@@ -28,10 +30,22 @@
 
 
 class Slave(beep.Initiator):
-    """Build slave."""
+    """BEEP initiator implementation for the build slave."""
 
     def __init__(self, ip, port, name=None, config=None, dry_run=False,
                  work_dir=None, keep_files=False):
+        """Create the build slave instance.
+        
+        @param ip: Host name or IP address of the build master to connect to
+        @param port: TCP port number of the build master to connect to
+        @param name: The name with which this slave should identify itself
+        @param config: The slave configuration
+        @param dry_run: Whether the build outcome should not be reported back
+            to the master
+        @param work_dir: The working directory to use for build execution
+        @param keep_files: Whether files and directories created for build
+            execution should be kept when done
+        """
         beep.Initiator.__init__(self, ip, port)
         self.name = name
         self.config = config
@@ -44,6 +58,11 @@
         self.keep_files = keep_files
 
     def greeting_received(self, profiles):
+        """Start a channel for the build orchestration profile, if advertised
+        by the peer.
+        
+        Otherwise, terminate the session.
+        """
         if OrchestrationProfileHandler.URI not in profiles:
             err = 'Peer does not support the Bitten orchestration profile'
             log.error(err)
@@ -94,6 +113,12 @@
         self.channel.send_msg(beep.Payload(xml), handle_reply)
 
     def handle_msg(self, msgno, payload):
+        """Handle either a build initiation or the transmission of a snapshot
+        archive.
+        
+        @param msgno: The identifier of the BEEP message
+        @param payload: The payload of the message
+        """
         if payload.content_type == beep.BEEP_XML:
             elem = xmlio.parse(payload.body)
             if elem.name == 'build':
@@ -120,7 +145,7 @@
                 shutil.copyfileobj(payload.body, archive_file)
             finally:
                 archive_file.close()
-            basedir = self.unpack_snapshot(msgno, project_dir, archive_name)
+            basedir = self.unpack_snapshot(project_dir, archive_name)
 
             try:
                 recipe = Recipe(self.build_xml, basedir, self.config)
@@ -130,8 +155,12 @@
                     shutil.rmtree(basedir)
                     os.remove(archive_path)
 
-    def unpack_snapshot(self, msgno, project_dir, archive_name):
-        """Unpack a snapshot archive."""
+    def unpack_snapshot(self, project_dir, archive_name):
+        """Unpack a snapshot archive.
+        
+        @param project_dir: Base directory for builds for the project
+        @param archive_name: Name of the archive file
+        """
         path = os.path.join(project_dir, archive_name)
         log.debug('Received snapshot archive: %s', path)
         try:
@@ -158,6 +187,15 @@
             raise beep.ProtocolError(550, 'Could not unpack archive (%s)' % e)
 
     def execute_build(self, msgno, recipe):
+        """Execute a build.
+        
+        Execute every step in the recipe, and report the outcome of each
+        step back to the server using an ANS message.
+        
+        @param msgno: The identifier of the snapshot transmission message
+        @param recipe: The recipe object
+        @type recipe: an instance of L{bitten.recipe.Recipe}
+        """
         log.info('Building in directory %s', recipe.ctxt.basedir)
         try:
             if not self.session.dry_run:
@@ -237,6 +275,7 @@
 
 
 def main():
+    """Main entry point for running the build slave."""
     from bitten import __version__ as VERSION
     from optparse import OptionParser
 

--- a/bitten/util/beep.py
+++ b/bitten/util/beep.py
@@ -7,14 +7,13 @@
 # you should have received as part of this distribution. The terms
 # are also available at http://bitten.cmlenz.net/wiki/License.
 
-
 """Minimal implementation of the BEEP protocol (IETF RFC 3080) based on the
 `asyncore` module.
 
 Current limitations:
- * No support for the TSL and SASL profiles.
- * No support for mapping frames (SEQ frames for TCP mapping).
- * No localization support (xml:lang attribute).
+ - No support for the TLS and SASL profiles.
+ - No support for mapping frames (SEQ frames for TCP mapping).
+ - No localization support (xml:lang attribute).
 """
 
 import asynchat
@@ -66,6 +65,15 @@
     }
 
     def __init__(self, code, message=None):
+        """Create the error.
+        
+        A numeric error code must be provided as the first parameter. A message
+        can be provided; if it is omitted, a standard error message will be
+        used in case the error code is known.
+        
+        @param code: The error code
+        @param message: An error message (optional)
+        """
         if message is None:
             message = ProtocolError._default_messages.get(code)
         Exception.__init__(self, 'BEEP error %d (%s)' % (code, message))
@@ -74,6 +82,12 @@
         self.local = True
 
     def from_xml(cls, xml):
+        """Create an error object from the given XML element.
+        
+        @param xml: The XML element representing the error
+        @type xml: An instance of L{bitten.util.xmlio.ParsedElement}
+        @return: The created C{ProtocolError} object
+        """
         elem = xmlio.parse(xml)
         obj = cls(int(elem.attr['code']), elem.gettext())
         obj.local = False
@@ -81,6 +95,10 @@
     from_xml = classmethod(from_xml)
 
     def to_xml(self):
+        """Create an XML representation of the error.
+        
+        @return: The created XML element
+        """
         return xmlio.Element('error', code=self.code)[self.message]
 
 
@@ -100,7 +118,7 @@
         self.eventqueue = []
 
     def run(self, timeout=15.0, granularity=5):
-        """Start listening to incoming connections."""
+        """Start the event loop."""
         granularity = timedelta(seconds=granularity)
         socket_map = asyncore.socket_map
         last_event_check = datetime.min
@@ -137,6 +155,13 @@
     communication with the connected peer.
     """
     def __init__(self, ip, port):
+        """Create the listener.
+        
+        @param ip: The IP address or host name to bind to
+        @type ip: a string
+        @param port: The TCP port number to bind to
+        @type port: an int
+        """
         EventLoop.__init__(self)
         asyncore.dispatcher.__init__(self)
         self.create_socket(socket.AF_INET, socket.SOCK_STREAM)
@@ -167,6 +192,8 @@
                                      first_channelno=2))
 
     def quit(self):
+        """Shutdown the listener, attempting to gracefully quit all active BEEP
+        sessions by first closing their respective channels."""
         if not self.sessions:
             self.close()
             return
@@ -382,6 +409,8 @@
         """
 
     def quit(self):
+        """Stops the build slave, attempting to gracefully quit the session by
+        closing all active channels."""
         self.terminate()
         asyncore.loop(timeout=10)
 
@@ -392,9 +421,9 @@
     def __init__(self, session, channelno, profile_cls):
         """Create the channel.
 
-        @param session The `Session` object that the channel belongs to
-        @param channelno The channel number
-        @param profile The associated `ProfileHandler` class
+        @param session: The L{Session} object that the channel belongs to
+        @param channelno: The channel number
+        @param profile_cls: The associated L{ProfileHandler} class
         """
         self.session = session
         self.channelno = channelno
@@ -421,9 +450,9 @@
         """Process a TCP mapping frame (SEQ).
         
         @param ackno: the value of the next sequence number that the sender is
-                      expecting to receive on this channel
+            expecting to receive on this channel
         @param window: window size, the number of payload octets per frame that
-                       the sender is expecting to receive on this channel
+            the sender is expecting to receive on this channel
         """
         self.windowsize = window
 
@@ -557,24 +586,44 @@
     def handle_disconnect(self):
         """Called when the channel this profile is associated with is closed."""
 
-    def handle_msg(self, msgno, message):
-        """Handle a MSG frame."""
+    def handle_msg(self, msgno, payload):
+        """Handle a MSG frame.
+        
+        @param msgno: The message identifier
+        @param payload: The C{Payload} of the message
+        """
         raise NotImplementedError
 
-    def handle_rpy(self, msgno, message):
-        """Handle a RPY frame."""
+    def handle_rpy(self, msgno, payload):
+        """Handle a RPY frame.
+        
+        @param msgno: The identifier of the referenced message
+        @param payload: The C{Payload} of the message
+        """
         pass
 
-    def handle_err(self, msgno, message):
-        """Handle an ERR frame."""
+    def handle_err(self, msgno, payload):
+        """Handle an ERR frame.
+        
+        @param msgno: The identifier of the referenced message
+        @param payload: The C{Payload} of the message
+        """
         pass
 
-    def handle_ans(self, msgno, ansno, message):
-        """Handle an ANS frame."""
+    def handle_ans(self, msgno, ansno, payload):
+        """Handle an ANS frame.
+        
+        @param msgno: The identifier of the referenced message
+        @param ansno: The answer number
+        @param payload: The C{Payload} of the message
+        """
         pass
 
     def handle_nul(self, msgno):
-        """Handle a NUL frame."""
+        """Handle a NUL frame.
+        
+        @param msgno: The identifier of the referenced message
+        """
         pass
 
 
@@ -590,10 +639,10 @@
         ]
         self.channel.send_rpy(0, Payload(xml))
 
-    def handle_msg(self, msgno, message):
+    def handle_msg(self, msgno, payload):
         """Handle an incoming message."""
-        assert message and message.content_type == BEEP_XML
-        elem = xmlio.parse(message.body)
+        assert payload and payload.content_type == BEEP_XML
+        elem = xmlio.parse(payload.body)
 
         if elem.name == 'start':
             channelno = int(elem.attr['number'])
@@ -626,27 +675,27 @@
             if not self.session.channels:
                 self.session.close()
 
-    def handle_rpy(self, msgno, message):
+    def handle_rpy(self, msgno, payload):
         """Handle a positive reply."""
-        if message.content_type == BEEP_XML:
-            elem = xmlio.parse(message.body)
+        if payload.content_type == BEEP_XML:
+            elem = xmlio.parse(payload.body)
             if elem.name == 'greeting':
                 if isinstance(self.session, Initiator):
                     profiles = [p.attr['uri'] for p in elem.children('profile')]
                     self.session.greeting_received(profiles)
 
-    def handle_err(self, msgno, message):
+    def handle_err(self, msgno, payload):
         """Handle a negative reply."""
         # Probably an error on connect, because other errors should get handled
         # by the corresponding callbacks
         # TODO: Terminate the session, I guess
-        if message.content_type == BEEP_XML:
-            raise ProtocolError.from_xml(message.body)
+        if payload.content_type == BEEP_XML:
+            raise ProtocolError.from_xml(payload.body)
 
     def send_close(self, channelno=0, code=200, handle_ok=None,
                    handle_error=None):
         """Send a request to close a channel to the peer."""
-        def handle_reply(cmd, msgno, ansno, message):
+        def handle_reply(cmd, msgno, ansno, payload):
             if cmd == 'RPY':
                 log.debug('Channel %d closed', channelno)
                 self.session.channels[channelno].close()
@@ -655,7 +704,7 @@
                 if handle_ok is not None:
                     handle_ok()
             elif cmd == 'ERR':
-                error = ProtocolError.from_xml(message.body)
+                error = ProtocolError.from_xml(payload.body)
                 log.debug('Peer refused to start channel %d: %s (%d)',
                           channelno, error.message, error.code)
                 if handle_error is not None:
@@ -668,18 +717,17 @@
     def send_start(self, profiles, handle_ok=None, handle_error=None):
         """Send a request to start a new channel to the peer.
         
-        @param profiles A list of profiles to request for the channel, each
-                        element being an instance of a `ProfileHandler`
-                        sub-class
-        @param handle_ok An optional callback function that will be invoked when
-                         the channel has been successfully started
-        @param handle_error An optional callback function that will be invoked
-                            when the peer refuses to start the channel
+        @param profiles: A list of profiles to request for the channel, each
+            element being an instance of a L{ProfileHandler} subclass
+        @param handle_ok: An optional callback function that will be invoked
+            when the channel has been successfully started
+        @param handle_error: An optional callback function that will be invoked
+            when the peer refuses to start the channel
         """
         channelno = self.session.channelno.next()
-        def handle_reply(cmd, msgno, ansno, message):
+        def handle_reply(cmd, msgno, ansno, payload):
             if cmd == 'RPY':
-                elem = xmlio.parse(message.body)
+                elem = xmlio.parse(payload.body)
                 for cls in [p for p in profiles if p.URI == elem.attr['uri']]:
                     log.debug('Channel %d started with profile %s', channelno,
                               elem.attr['uri'])
@@ -689,7 +737,7 @@
                 if handle_ok is not None:
                     handle_ok(channelno, elem.attr['uri'])
             elif cmd == 'ERR':
-                elem = xmlio.parse(message.body)
+                elem = xmlio.parse(payload.body)
                 text = elem.gettext()
                 code = int(elem.attr['code'])
                 log.debug('Peer refused to start channel %d: %s (%d)',
@@ -710,7 +758,17 @@
 
     def __init__(self, data=None, content_type=BEEP_XML,
                  content_disposition=None, content_encoding=None):
-        """Initialize the payload."""
+        """Initialize the payload object.
+        
+        @param data: The body of the MIME message. This can be either:
+            - a string,
+            - a file-like object providing a C{read()} function,
+            - an XML element, or
+            - C{None}
+        @param content_type: the MIME type of the payload
+        @param content_disposition: the filename for disposition of the data
+        @param content_encoding: the encoding of the data
+        """
         self._hdr_buf = None
         self.content_type = content_type
         self.content_disposition = content_disposition
@@ -728,6 +786,10 @@
             self.body = data
 
     def read(self, size=None):
+        """Return the specified range of the MIME message.
+        
+        @param size: the number of bytes to read
+        """
         if self._hdr_buf is None:
             hdrs = []
             if self.content_type:
@@ -757,6 +819,10 @@
         return ret_buf
 
     def parse(cls, string):
+        """Create a C{Payload} object from the given string data.
+        
+        @param string: The string containing the MIME message.
+        """
         message = email.message_from_string(string)
         content_type = message.get('Content-Type')
         content_disposition = message.get('Content-Disposition')
@@ -768,16 +834,17 @@
 
 class FrameProducer(object):
     """Internal class that emits the frames of a BEEP message, based on the
-    `asynchat` `push_with_producer()` protocol.
+    C{asynchat} C{push_with_producer()} protocol.
     """
     def __init__(self, channel, cmd, msgno, ansno=None, payload=None):
         """Initialize the frame producer.
         
-        @param channel the channel the message is to be sent on
-        @param cmd the BEEP command/keyword (MSG, RPY, ERR, ANS or NUL)
-        @param msgno the message number
-        @param ansno the answer number (only for ANS messages)
-        @param payload the message payload (an instance of `Payload`)
+        @param channel: The channel the message is to be sent on
+        @param cmd: The BEEP command/keyword (MSG, RPY, ERR, ANS or NUL)
+        @param msgno: The message number
+        @param ansno: The answer number (only for ANS messages)
+        @param payload: The message payload
+        @type payload: an instance of L{Payload}
         """
         self.session = channel.session
         self.channel = channel