IBM Advanced Function Printing (AFP) - Components

Components

The AFP architecture consists of a number of sub-architectures:

• MO:DCA-P (Mixed Object:Document Content Architecture-Presentation), the Page Description Language file format that describes the text and graphics on a page. The 'Mixed Object' moniker refers to the fact that a MO:DCA file can contain multiple types of objects, including text, images, vector graphics, and even objects marked as 'barcodes'. An application can simply include a string of digits along with controls that identify a specific type of barcode, and the rendering of bars will be done on the output platform (physical printer hardware or software emulation). A MO:DCA file consists of a sequential, ordered hierarchy of independent objects - documents, pages, data objects, and resource objects such as fonts and ICC profiles. Each object is delimited by begin/end structures, and objects to be rendered specify presentation parameters and resource requirements in structures called "environment groups". Since the pages in MO:DCA documents appear in sequential order, presentation can start as soon as the first page is received. The MO:DCA format is comparable to other PDLs that specify distinct pages such as PDF. MO:DCA-P is sometimes called AFPDS (AFP Data Stream).

• IPDS Intelligent Printer Data Stream. This is the bi-directional protocol used between the host server and the printer. It is used to send the page-level data to the printer and to signal errors and accounting information back to the server. The IPDS protocol also allows the server to query a printer's available resources (e.g. available memory, fonts, input trays, etc.). It's comparable to protocols like Internet Printing Protocol.

• Bar Code Object Content Architecture (BCOCA), which is used to describe and generate bar codes.

• Color Management Object Content Architecture (CMOCA), which defines resources that carry color management information, such as ICC profiles, tone transfer curves, and halftones.

• Graphics Object Content Architecture for AFP (AFP GOCA), which is used to define and generate vector graphics.

• Image Object Content Architecture (IOCA), which is used to define and generate raster images.

• Presentation Text Object Content Architecture (PTOCA), which is used to define and generate text.

Specifications defining all of the AFP sub-architectures can be found at the AFP Consortium.

AFP also supports other industry-standard data formats using the concept of AFP object containers; examples are TIFF, GIF, JPEG (JFIF), EPS, and PDF. These objects can be mixed as peer objects on an AFP page with native AFP objects such as BCOCA, AFP GOCA, IOCA, and PTOCA objects.