The SOPE XML Processing libraries contain: SAX2 implementation for Objective-C, SaxObjC driver bundles ( libxml2, CoreFoundation XML, libical, expat, plists, pyx ), an attempt to implement DOM on top of SaxObjC, an XML-RPC implementation (without a transport layer).
The SOPE Core libraries (sope-core) contain various Foundation extensions (EOControl and NGExtensions) and a java.io like stream and socket library (NGStreams).
The MIME libraries (sope-mime) contain classes for processing MIME entities (NGMime), a full IMAP4 implementation (NGImap4), prototypical POP3 and SMTP processors (NGMail).
The sope-appserver package is a framework for developing web applications and services. The name "SOPE" (SKYRiX Object Publishing Environment) is inspired by ZOPE ;-)
The LDAP libraries (sope-ldap) contains an Objective-C wrapper for libldap.
The SOPE iCal package (sope-ical) contains a SaxObjC driver for processing iCalendar files using libical (iCalSaxDriver) and a library which contains model classes for iCalendar/vCard objects.
SOPE contains a fork of the GNUstep Database Library (GDL) v1.0 which is used
primarily by OpenGroupware.org. GDL is mostly compatible with the EOF 1.1
by NeXT Computer Inc., so while it has some similiarity with newer
WebObjects EOF versions, it misses a lot of new things.
In case you are looking for an EOF 4 compatible database library which can be used together with SOPE, consider GDL 2, which is in active development.
SOPE:X are specific SOPE enhancements to developer with the Xcode IDE on MacOSX Panther and later. It includes Xcode project templates as well as some awesome features like running a SOPE application as an AppKit application (.app wrapper).
Note: the diagram is still mostly valid, yet the individual subcomponents have moved in SOPE 4.3 (eg MIME is not contained in sope-core anymore but moved to an own top-level package sope-mime).