Patent Application
20140168691
The invention relates to the field of computer systems. Particularly, the invention relates to pipes and filters architecture pattern.
Printers are common peripheral devices attached to computers. A printer allows a computer user to make a hard copy of documents that are created in a variety of applications and programs on a computer. To function properly, a channel of communication is established (e.g., via a network connection) between the printer and the computer to enable the printer to receive commands and information from the host computer.
Once a connection is established between a workstation and the printer, printing software is implemented at a print server to manage a print job from order entry and management through the complete printing process. The printing software may implement a pipes and filters architectural pattern (pipes/filters pattern) to process print job data streams. A pipes/filters pattern provides a structure for systems that process a stream of data, where each processing step is encapsulated in a filter component. Data is passed through pipes between adjacent filters.
A pipe/filter pattern is sequential in behavior, with each filter receiving an output of a previous filter as its input. Thus, pipes/filters patterns provide the benefit of breaking tasks into smaller units, resulting in increased flexibility and maintainability. A problem with the pipes/filters patterns is that it does not lend itself to solving problems that require look ahead capability. For instance, an individual filter is required to buffer sufficient information until it has that information prior to sending the buffered contents downstream.
Accordingly, a mechanism to solve pipeline look ahead problems without requiring a filter to buffer data large amounts of data is desired.
In one embodiment a computer generated method is disclosed. The method includes each filter within a chain of filters of a pipes and filters architectural pattern declaring a pass requirement to indicate a number of times the filter is to be processed to produce final form data and processing a stream of data at each filter within the chain of filters to produce the final form data
In another embodiment, a print server is disclosed. The print server includes a printing software product that includes a pipes and filters architectural pattern having chain of filters, wherein each filter within a chain of filters of a pipes and filters architectural pattern declares a pass requirement to indicate a number of times the filter is to be processed to produce final form data and processes a stream of data to produce the final form data.
A better understanding of the present invention can be obtained from the following detailed description in conjunction with the following drawings, in which:
A multiple pass pipe/filter design pattern mechanism is described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well-known structures and devices are shown in block diagram form to avoid obscuring the underlying principles of the present invention.
Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
Network 106 may be a local area network (LAN) or any other network over which print requests may be submitted to a remote printer or print server. Communications link 104 may be in the form of a network adapter, docking station, or the like, and supports communications between data processing system 102 and network 106 employing a network communications protocol such as Ethernet, the AS/400 Network, or the like.
According to one embodiment, network 106 includes a print server 108 that serves print requests over network 106 received via communications link 110 between print server 108 and network 106. Print server 108 subsequently transmits the print requests via communications link 110 to one of printers 109 for printing, which are coupled to network 106 via communications links 111.
In one embodiment, a print application at data processing system 102 allows a user to select the desired print server 108 and submit requests for service requests to printer 109 via print server 108 over network 106. In a further embodiment, the print application implements the (Advanced Function Presentation) AFP™ presentation system developed by International Business Machines Corporation to represent documents in a data format that is independent of the methods that are utilized to capture or create those documents.
According to the AFP system, documents may include combinations of text, image, graphics, and/or barcode objects in device and resolution independent formats. Documents may also include and/or reference fonts, overlays, and other resource objects, which are required at presentation time to present the data properly. An AFP system also implements Structured Field commands (or Structured Fields). A Structured Field is an instruction (or collection of instructions) to an AFP print driver. Each Structured Field command is an individual data record that has a specific format and each unique Structured Field command has a unique function that it performs.
In other embodiments, additional/alternative presentation architectures may be implemented at the print application. However in an AFP embodiment, the print application provides a Mixed Object Document Content Architecture (MO:DCA) data stream to print server 108. In such an embodiment, the AFP MO:DCA data streams are object-oriented streams including, among other things, data objects, page objects, and resource objects. In a further embodiment, AFP MO:DCA data streams include a Resource Environment Group (REG) that is specified at the beginning of the AFP document, before the first page. When the AFP MO:DCA data streams are processed by print server 108, the REG structure is encountered first and causes server 108 to download any of the identified resources that are not already present in the printer.
Although described as separate entities, other embodiments may include print server 108 being incorporated in one or more of the printers 109. In yet further embodiments, the print server and printer may be physically separate entities. Therefore, the data processing system network depicted in
According to one embodiment, print server 108 implements a printing software product that manages the printing of documents from data processing system 102 and one or more of printers 109. In other embodiments, the printing software product manages printing of documents from multiple data processing systems 102 to the one or more printers 109. In one embodiment, the printing software product may be implemented using either InfoPrint Manager (IPM) or InfoPrint ProcessDirector (IPPD), although other types of printing software may be used instead. In a further embodiment, the print application at data processing system 102 interacts with the printing software product to provide for efficient transmission of print jobs.
According to one embodiment, the printing software product implements a pipe/filter design pattern to process AFP structured fields. In such an embodiment, the printing software product includes a chain of filters that perform look ahead processing.
According to one embodiment, each filter declares its pass requirement prior to processing in order to indicate the number of times the filter is to be processed to produce its final form data. Thus, the filter is assured that it will receive the same data on each pass, while gathering and subsequently utilizing the look ahead information.
As shown in
If the filter requires N passes, a partial chain up to and including the current filter process the data, processing block 330. At processing block 340, the filter is informed of the current pass number on which the first filter is operating. At decision block 350, it is determined whether the current filter has run for Nth time. If so, the chain is extended to the next filter, with control being returned to decision block 310. Otherwise, control is returned to processing block 330, where partial chain is again processed. Accordingly, the chain is extended to the next multi-pass filter where the process is repeated. When the complete pipeline is run and the final filter in the chain is run its required number of passes, the chain is complete.
Reviewing the process within the context of
The second segment is run similarly, where Filters C and D are given their pass numbers. Note that the first segment is run again as part of the second segment. However, those filter's pass numbers remain unchanged. The complete final segment is run when each multi-pass filter is run a minimum of its number of required passes. This ensures that each filter passes final form data to the next, while minimizing the number of times each filter is run. Filter E runs only once in this design, thus minimizing I/O.
Computer system 400 further comprises a random access memory (RAM) or other dynamic storage device 425 (referred to herein as main memory), coupled to bus 420 for storing information and instructions to be executed by processor 410. Main memory 425 also may be used for storing temporary variables or other intermediate information during execution of instructions by processor 410. Computer system 400 also may include a read only memory (ROM) and or other static storage device 426 coupled to bus 420 for storing static information and instructions used by processor 410.
A data storage device 425 such as a magnetic disk or optical disc and its corresponding drive may also be coupled to computer system 400 for storing information and instructions. Computer system 400 can also be coupled to a second I/O bus 450 via an I/O interface 430. A plurality of I/O devices may be coupled to I/O bus 450, including a display device 424, an input device (e.g., an alphanumeric input device 423 and or a cursor control device 422). The communication device 421 is for accessing other computers (servers or clients). The communication device 421 may comprise a modem, a network interface card, or other well-known interface device, such as those used for coupling to Ethernet, token ring, or other types of networks.
Embodiments of the invention may include various steps as set forth above. The steps may be embodied in machine-executable instructions. The instructions can be used to cause a general-purpose or special-purpose processor to perform certain steps. Alternatively, these steps may be performed by specific hardware components that contain hardwired logic for performing the steps, or by any combination of programmed computer components and custom hardware components.
Elements of the present invention may also be provided as a machine-readable medium for storing the machine-executable instructions. The machine-readable medium may include, but is not limited to, floppy diskettes, optical disks, CD-ROMs, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, propagation media or other type of media/machine-readable medium suitable for storing electronic instructions. For example, the present invention may be downloaded as a computer program which may be transferred from a remote computer (e.g., a server) to a requesting computer (e.g., a client) by way of data signals embodied in a carrier wave or other propagation medium via a communication link (e.g., a modem or network connection).
Whereas many alterations and modifications of the present invention will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that any particular embodiment shown and described by way of illustration is in no way intended to be considered limiting. Therefore, references to details of various embodiments are not intended to limit the scope of the claims, which in themselves recite only those features regarded as essential to the invention.
