A precise definition of build item would state that a build item is any directory that contains an Abuild.conf. Perhaps a more useful definition would say that a build item is the basic object that participates in abuild's object-oriented view of a software build. A build item provides some service within a build tree. Most build items build some kind of code: most often a library, executable, or Java archive. Build items may provide other kinds of services as well. For example, a build item may implement a code generator, support for a new compiler, or the ability to make use of a third-party software library. In addition, a build item may have certain attributes including a list of dependencies, a list of supported flags, information about what types of platforms the build item may be built on, a list of traits, and other non-dependency relationships to other build items. Each of these concepts is explored in more depth later in the document.

All build items that provide a service are required to have a name. Build item names must be unique within their build tree and all other build trees accessible to their build tree since the build item name is how abuild addresses a build item. Build item names consist of period-separated segments. Each segment may contain mixed case alphanumeric characters, underscores, and dashes. Build item names are case-sensitive.

The primary mechanism for describing build items is the Abuild.conf file. This file consists of colon-separated key/value pairs. A complete description of the Abuild.conf file may be found in Chapter 15, The Abuild.conf File. In the mean time, we will introduce keys as they become relevant to our discussion.