- <listitem><para>&asn;, which provides a C representation of the Z39.50
- protocol packages (PDUs).
- </para></listitem>
- <listitem><para>&odr;, which encodes and decodes the packages according
- to the BER specification.
- </para></listitem>
- <listitem><para>&comstack;, which exchanges the encoded packages with
- a peer process over a network.
- </para></listitem>
+ <listitem>
+ <para>A client or server application (or both).
+ This layer includes ZOOM and the generic frontend server.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ The second layer provides a C represenation of the
+ protocol units (packages) for Z39.50 ASN.1, ILL ASN.1,
+ SRU.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ The third layer encodes and decodes protocol data units to
+ simple packages (buffer with certain length). The &odr; module
+ encodes and decodes BER whereas the HTTP modules encodes and
+ decodes HTTP ruquests/responses.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ The lowest layer is &comstack; which exchanges the encoded packages
+ with a peer process over a network.
+ </para>
+ </listitem>