Patent Publication Number: US-2018041224-A1

Title: Data value suffix bit level compression

Description:
BACKGROUND 
     The present invention relates generally to the field of data compression, and more particularly to the compression of common suffixes of data values. 
     A number of compression techniques exist for compressing data values within database tables. The compression techniques include the following steps: analyzing the data values to build compression dictionaries, compressing the data values using the compression dictionaries, and storing the compressed data. A compression dictionary may be thought of as a shorthand version of the original data values. Data compression helps to reduce the overall size of a database and improves the performance of input/output (I/O) intensive workloads because the data is stored in fewer pages in the database. 
     SUMMARY OF THE INVENTION 
     Embodiments of the present invention include a method, computer program product, and system for the compression of common suffixes of data values. In one embodiment, one or more data values from a database table in a database are determined. Each data value of the one or more data values are split into one or more individual sections when the one or more data values include two or more characters. The splitting of each data value of the one or more data values results in each section of the one or more individual sections being a single character. Each section of the one or more individual sections is converted into one or more equivalent binary data values. “N” bits of prefix data in the one or more equivalent binary data values are ignored to create one or more common suffixes in the one or more equivalent binary data values. The one or more common suffixes are encoded. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a functional block diagram of a computing environment, in accordance with an embodiment of the present invention; 
         FIG. 2  depicts a flowchart of a program for the compression of common suffixes of data values, in accordance with an embodiment of the present invention; 
         FIG. 3A  depicts an example table demonstrating suffix compression, in accordance with an embodiment of the present invention; 
         FIG. 3B  depicts an example data page following suffix compression, in accordance with an embodiment of the present invention; and 
         FIG. 4  depicts a block diagram of components of the computing environment of  FIG. 1 , in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention provide for the compression of common suffixes of data values stored to a database table. Current data compression techniques, of which there are many, include the steps of analyzing data, building compression dictionaries based on the analyzed data, compressing the data using the compression dictionaries, and storing the compressed data. Huffman encoding is one such compression technique. With Huffman encoding, frequency histograms are built based on the various data values to be compressed. If too many data values are present and the number of distinct values are too high, there may be a large amount of stress on the memory resources of the computing device building the histograms. Pruning the histograms may minimize the impact of memory constraints but the pruning may negatively affect the compression rates. 
     Embodiments of the present invention recognize that there may be a method, computer program product, and computer system for the compression of common suffixes of data values stored to a database table. Embodiments of the present invention may ignore the prefix of multiple data values leaving a common suffix for each data value, which may then be compressed. Using the method, computer program product, and computer system may result in needing less memory to store the data histograms used in compressing the data values, better compression rates due to smaller code size, and better use of memory resources during query runtime. Runtime may be defined as the period of time during which a computer program, in this case, a database query, is executing. 
     The present invention will now be described in detail with reference to the Figures. 
       FIG. 1  is a functional block diagram illustrating a computing environment, generally designated  100 , in accordance with one embodiment of the present invention.  FIG. 1  provides only an illustration of one implementation and does not imply any limitations with regard to the systems and environments in which different embodiments may be implemented. Many modifications to the depicted embodiment may be made by those skilled in the art without departing from the scope of the invention as recited by the claims. 
     In an embodiment, computing environment  100  includes server device  120  connected to network  110 . In example embodiments, computing environment  100  may include other computing devices (not shown) such as smartwatches, cell phones, smartphones, wearable technology, phablets, tablet computers, laptop computers, desktop computers, other computer servers or any other computer system known in the art, interconnected with server device  120  over network  110 . 
     In example embodiments, server device  120  may connect to network  110 , which enables server device  120  to access other computing devices and/or data not directly stored on server device  120 . Network  110  may be, for example, a local area network (LAN), a telecommunications network, a wide area network (WAN) such as the Internet, or any combination of the three, and include wired, wireless, or fiber optic connections. Network  110  may include one or more wired and/or wireless networks that are capable of receiving and transmitting data, voice, and/or video signals, including multimedia signals that include voice, data, and video information. In general, network  110  can be any combination of connections and protocols that will support communications between server device  120  and any other computing device connected to network  110 , in accordance with embodiments of the present invention. In an embodiment, data received by another computing device in computing environment  100  (not shown) may be communicated to server device  120  via network  110 . 
     In embodiments of the present invention, server device  120  may be a laptop, tablet, or netbook personal computer (PC), a desktop computer, a personal digital assistant (PDA), a smartphone, a standard cell phone, a smart-watch or any other wearable technology, or any other hand-held, programmable electronic device capable of communicating with any other computing device within computing environment  100 . In certain embodiments, server device  120  represents a computer system utilizing clustered computers and components (e.g., database server computers, application server computers, etc.) that act as a single pool of seamless resources when accessed by elements of computing environment  100 . In general, server device  120  is representative of any electronic device or combination of electronic devices capable of executing computer readable program instructions. Computing environment  100  may include one server device  120  or any number of server device  120 . Server device  120  may include components as depicted and described in further detail with respect to  FIG. 4 , in accordance with embodiments of the present invention. 
     In an embodiment, server device  120  includes database  122  and suffix compression program  124 . According to embodiments of the present invention, database  122  may be storage that may be written to and/or read by suffix compression program  124 . In one embodiment, database  122  resides on server device  120 . In other embodiments, database  122  may reside on any other device (not shown) in computing environment  100 , in cloud storage or on another computing device accessible via network  110 . In yet another embodiment, database  122  may represent multiple storage devices within server device  120 . Database  122  may be implemented using any volatile or non-volatile storage media for storing information, as known in the art. For example, database  122  may be implemented with a tape library, optical library, one or more independent hard disk drives, multiple hard disk drives in a redundant array of independent disks (RAID), solid-state drives (SSD), or random access memory (RAM). Similarly, database  122  may be implemented with any suitable storage architecture known in the art, such as a relational database, an object-oriented database, or one or more tables. In an embodiment of the present invention, suffix compression program  124  and any other programs and applications (not shown) operating on server device  120  may store, read, modify, or write data to database  122 . Examples of data stored to database  122  include the input data values being loaded into the database tables or the frequency histograms determined by suffix compression program  124 . 
     According to embodiments of the present invention, suffix compression program  124  may be a program, a subprogram of a larger program, an application, a plurality of applications, or mobile application software, which functions to compress common suffixes of data values stored to a database table. A program is a sequence of instructions written by a programmer to perform a specific task. Suffix compression program  124  may run by itself but may be dependent on system software (not shown) to execute. In one embodiment, suffix compression program  124  functions as a stand-alone program residing on server device  120 . In another embodiment, suffix compression program  124  may be included as a part of server device  120 . In yet another embodiment, suffix compression program  124  may work in conjunction with other programs, applications, etc., found on server device  120  or in computing environment  100 . In yet another embodiment, suffix compression program  124  may be found on other computing devices (not shown) in computing environment  100  which are interconnected to server device  120  via network  110 . 
     According to embodiments of the present invention, suffix compression program  124  functions to compress common suffixes of data values. According to an embodiment of the present invention, suffix compression program  124  allows suffixes of data values in a database table to be compressed which may result in needing less memory requirements, better compression rates, and better use of memory during query runtime. In an embodiment, suffix compression program  124  on server device  120  compresses the data values of a table stored to database  122 . 
       FIG. 2  is a flowchart of workflow  200  depicting a method for the compression of common suffixes of data values, in accordance with an embodiment of the present invention. In one embodiment, the method of workflow  200  is performed by suffix compression program  124 . In an alternative embodiment, the method of workflow  200  may be performed by any other program working with suffix compression program  124 . In an embodiment, a user, via a user interface (not shown), may invoke workflow  200  upon the user creating a new database table. In another embodiment, workflow  200  may be invoked upon a program initiating a data load into a database table. In an alternative embodiment, a user may invoke workflow  200  upon accessing suffix compression program  124 . 
     In an embodiment, suffix compression program  124  retrieves data values (step  202 ). In other words, based on the request of a user or a program, suffix compression program  124  retrieves the data values that require compression from a database table. In an embodiment, suffix compression program  124  retrieves data values from database  122  included on server device  120 . For example, the data values “A5” (data value serial number 1 in column  302 A), “8Au” (data value serial number 2 in column  302 A), and “n” (data value serial number 3 in column  302 A), are retrieved from column  304 A, as shown in Table  300  in  FIG. 3A . 
     In an embodiment, suffix compression program  124  splits data values (step  204 ). In other words, suffix compression program  124  splits the data values into individual sections (i.e., single characters) when the data value consists of two or more characters. Splitting the data values into individual sections allows suffix compression program  124  to use any repetitive suffixes of the individual sections and build the frequency histograms of the data values at the individual section level. In an embodiment, suffix compression program  124  splits the data values, where possible, retrieved from database  122  on server device  120 . For example, as shown in column  308 A in Table  300  in  FIG. 3A , the data value “A5” is split into the two sections “A” and “5” and the data value “8Au” is split into the three sections “8”, “A”, and “u”. In some embodiments, data values cannot or do not need to be split. For example, the data value “n” is not split since it is not comprised of multiple characters. 
     In an embodiment, suffix compression program  124  converts data values (step  206 ). In other words, suffix compression program  124  converts each split section of the original data values into an equivalent binary data value. Converting the split sections of the original data values to the equivalent binary data values is done to allow suffix compression that may allow for less utilization of memory resources and better utilization of memory resources during query runtime. Runtime is defined as the period of time during which a computer program, in this case, a database query, is executing. In an embodiment, suffix compression program  124  converts the split sections of the original data values to the equivalent binary data value using any of the conversion techniques known in the art. For example, as shown in column  310 A in Table  300  in  FIG. 3A , section “A” of data value “A5” is converted to binary value “01000001” and section “5” of data value “A5” is converted to binary value “00110101”. Similarly, section “8”, section “A”, and section “u” of data value “8Au” are converted to binary values “00111000”, “01000001”, and “01110101”, respectively. In addition, data value “n” is converted to binary value “01101110”. 
     In an embodiment, suffix compression program  124  ignores bits (step  208 ). In other words, suffix compression program  124  ignores “N” bits of prefix data in each of the binary data values to create common suffixes in each of the binary data values where possible. In an embodiment, the value of “N” is defined by the programmer of the database. In another embodiment, the value of “N” is determined by an intelligent system via a sampling of the binary data values stored to a database table (e.g., database  122 ). In yet another embodiment, the value of “N” is determined by an intelligent system via a sampling of the original data values gathered from the source of the original data values. In an embodiment, suffix compression program  124  ignores “N” bits of prefix data in each of the converted binary data values. For example, as shown in column  312 A in Table  300  in  FIG. 3A , two bits of prefix data are ignored in each of the converted binary data values (in column  310 A) which results in six bit suffix “000001” remaining from “01000001” (section “A”), six bit suffix “110101” remaining from “00110101” (section “5”), six bit suffix “111000” remaining from “00111000” (section “8”), six bit suffix “000001” remaining from “01000001” (section “A”), six bit suffix “110101” from “01110101” (section “u”), and six bit suffix “101110” from “01101110” (data value “n”). 
     In an embodiment, suffix compression program  124  determines suffix frequency (step  210 ). In other words, suffix compression program  124  compares each remaining suffix after the “N” prefix bits are ignored to determine the frequency of repeating suffixes (i.e., the number of occurrences of each suffix across all of the sections of all of the data values). In an embodiment, the number of occurrences of each suffix is used to build a histogram that is subsequently used to create the compression dictionary code for each suffix. In an embodiment, suffix compression program  124  determines the frequency of occurrence of each suffix. For example, as shown in column  314 A in Table  300  in  FIG. 3A , six bit suffix “000001” occurs two times in column  312 A, six bit suffix “110101” occurs two times in column  312 A, six bit suffix “111000” occurs one time in column  312 A, and six bit suffix “101110” occurs one time in column  312 A. 
     In an embodiment, suffix compression program  124  encodes suffix (step  212 ). In other words, the suffixes created from ignoring “N” bits of data in the original binary data values are encoded to create unique dictionary codes for each unique common suffix. In an embodiment, Huffman encoding is used to encode the suffixes. Huffman encoding is an algorithm used to create a particular type of optimal encoding that is used for lossless data compression. The output from the Huffman algorithm can be viewed as a variable-length code table for encoding a source symbol (such as a data value in a database table). The Huffman algorithm derives the table from the estimated probability or frequency of occurrence for each possible value of the data value. Values that are more common are represented using fewer bits than values that are less common. In another embodiment, any method that uses frequency distribution information of data values may be used to encode the suffixes. In an embodiment, suffix compression program  124  uses Huffman encoding to encode the suffixes of the original data values stored to database  122  in binary form. For example, as shown in column  316 A in Table  300  in  FIG. 3A , the dictionary code, based on the frequency of occurrence shown in column  314 A, is shown for each suffix. The dictionary code for suffix “000001”, which occurs twice, is “0”. The dictionary code for suffix “110101”, which also occurs twice, is “1”. The dictionary code for suffix “111000”, which occurs once, is “00”. The dictionary code for suffix “101110”, which occurs once, is “01”. Since there are four unique values of the suffix values, the suffix values can be depicted optimally by using binary codes that are, at most, two bits. In addition, Huffman encoding dictates that values that occur more frequently can be depicted in fewer bits than values that occur more frequently. Therefore, the two suffixes that occur twice can be depicted by “0” and “1” (fewer bits) while the values that occur only once can be depicted by “00” and “01” (more bits). 
     In an embodiment, suffix compression program  124  determines the box (step  214 ). In other words, suffix compression program  124  determines the appropriate box, based on the “N” ignored prefix bits, on the data page to assign the determined dictionary codes. In an embodiment, the box is an area on the data page where specific data is stored. In an embodiment, the number of unique prefix bits across all of the data values in binary format are used to determine the number of boxes required on the data page. In an embodiment, suffix compression program  124  determines the number of unique prefix codes for the data values in the data table. For example, as shown in column  318 A in Table  300  in  FIG. 3A , there are two unique prefixes (“00” and “01”) for the data values in Table  300 . Therefore, only two boxes (box “0” and box “1”, as shown in column  320 A in table  300  in  FIG. 3A  are required. The two boxes are also represented in data page example  350  in  FIG. 3B  as box 0  354 B and box 1  358 B found in data page  352 B. 
     In an embodiment, suffix compression program  124  populates the data page (step  216 ). In other words, suffix compression program  124  populates the data page with the compressed suffix values using the previously determined number of boxes. In an embodiment, the data page is a representation of the physical structure of the memory (e.g., hard disk) where the compressed data values are stored. In an embodiment, the data page may be stored to any storage medium that can be accessed by the database software. In an embodiment, compressed suffix values are stored to one or more boxes in the data page. For example, as shown in data page example  350  in  FIG. 3B , compressed suffix value “100” is stored to box 0  354 B and compressed suffix value “00101” is stored to box 1  358 B. 
     The following discussion will concern data page example  350  in  FIG. 3B . In an embodiment, suffix compression program  124  may determine the following for the data page: the section offset for each box, the value map for the data page, the value map offset, and the box index for the data page. 
     In an embodiment, the section offset for each box allows a user to read the compressed suffix values of sections stored in each box. Within a given section offset, a value of “1” indicates the start of a compressed suffix value of a section and a value of “0” that precedes another “0” represents continuation in a compressed suffix value of a section and a value of “0” that precedes a “1” ends a compressed suffix value of a section. For example, section offset  356 B in box 0  354 B in data page  352 B includes the information “110” indicating that there are two compressed suffix values in box 0  354 B (i.e., the first compressed suffix value is one bit in length as indicated by the “1” in “110” and the second compressed suffix value is two bits in length as indicated by the “10” in “110”). In other words, the first “1” in “110” must indicate a one-bit compressed suffix value since the “1” is not followed by a “0”. The second “1” in “110” is followed by a single “0” (and nothing more) which indicates that the next compressed suffix value is two bits long. The compressed suffix values in box 0  354 B are “100” and section offset  356 B indicates that the compressed suffix values are one bit long and two bits long. Therefore, the compressed suffix values are “1” and “00”. 
     For another example, consider box 1  358 B, with compressed suffix value “00101”, and section offset  360 B, with information “11110”, in data page  352 B. Section offset  360 B indicates the following: a one bit compressed suffix value, another one bit compressed suffix value, yet another one bit compressed suffix value, and a two bit compressed suffix value. Therefore, the compressed suffix values in box 1  358 B are “0”, “0”, “1”, and “01”. 
     In an embodiment, the value map determines which boxes to read, and in what order, to get ordered sections that make up a data value. In the embodiment, the value map offset determines the length, in bits, of each data value. Used in concert, the value map and the value map offset allow a user to read the data values in the correct order. The example depicted in data page example  350  in  FIG. 3B  indicates that value map  362 B includes the information “100111”. Value map offset  364 B, which includes the information “101001”, is comparable to section offset  356 B and section offset  360 B in that a “1” indicates the start of a value and a “0” that precedes another “0” represents continuation in a data value and a value of “0” that precedes a “1” ends a data value. Therefore, value map offset  364 B indicates that the first data value is two bits long, the second data value is three bits long, and the third data value is one bit long. Using the value map information of “100111”, the first data value (which is two bits long) is read from box “1”, then box “0” (the “10” of “100111”). The second data value (which is three bits long) is read from box “0”, then box “1”, and then box “1” (the “011” of “100111”). The third data value (which is one bit long) is read from box “1” (the last “1” of “100111”). 
     In an embodiment, the box index indicates the prefix for every data value within a box. In addition, the box index is used to stitch the data values back together. As shown in the example depicted in box index  366 B in data page example  350  in  FIG. 3B , the compressed suffix values within box 0  354 B have a prefix of “00” while the compresses suffix values within box 1  358 B have a prefix of “01”. 
     It should be noted that the use of a suffix compression technique such as suffix compression program  124  is compatible with other encoding techniques such as pure dictionary encoding and minus encoding. In addition, suffix encoding may be applied to data values already encoded by other encoding techniques known in the art such as prefix encoding and pure dictionary encoding. 
       FIG. 4  depicts computer system  400 , which is an example of a system that includes suffix compression program  124 . Computer system  400  includes processors  401 , cache  403 , memory  402 , persistent storage  405 , communications unit  407 , input/output (I/O) interface(s)  406  and communications fabric  404 . Communications fabric  404  provides communications between cache  403 , memory  402 , persistent storage  405 , communications unit  407 , and input/output (I/O) interface(s)  406 . Communications fabric  404  can be implemented with any architecture designed for passing data and/or control information between processors (such as microprocessors, communications and network processors, etc.), system memory, peripheral devices, and any other hardware components within a system. For example, communications fabric  404  can be implemented with one or more buses or a crossbar switch. 
     Memory  402  and persistent storage  405  are computer readable storage media. In this embodiment, memory  402  includes random access memory (RAM). In general, memory  402  can include any suitable volatile or non-volatile computer readable storage media. Cache  403  is a fast memory that enhances the performance of processors  401  by holding recently accessed data, and data near recently accessed data, from memory  402 . 
     Program instructions and data used to practice embodiments of the present invention may be stored in persistent storage  405  and in memory  402  for execution by one or more of the respective processors  401  via cache  403 . In an embodiment, persistent storage  405  includes a magnetic hard disk drive. Alternatively, or in addition to a magnetic hard disk drive, persistent storage  405  can include a solid state hard drive, a semiconductor storage device, read-only memory (ROM), erasable programmable read-only memory (EPROM), flash memory, or any other computer readable storage media that is capable of storing program instructions or digital information. 
     The media used by persistent storage  405  may also be removable. For example, a removable hard drive may be used for persistent storage  405 . Other examples include optical and magnetic disks, thumb drives, and smart cards that are inserted into a drive for transfer onto another computer readable storage medium that is also part of persistent storage  405 . 
     Communications unit  407 , in these examples, provides for communications with other data processing systems or devices. In these examples, communications unit  407  includes one or more network interface cards. Communications unit  407  may provide communications through the use of either or both physical and wireless communications links. Program instructions and data used to practice embodiments of the present invention may be downloaded to persistent storage  405  through communications unit  407 . 
     I/O interface(s)  406  allows for input and output of data with other devices that may be connected to each computer system. For example, I/O interface  406  may provide a connection to external devices  408  such as a keyboard, keypad, a touch screen, and/or some other suitable input device. External devices  408  can also include portable computer readable storage media such as, for example, thumb drives, portable optical or magnetic disks, and memory cards. Software and data used to practice embodiments of the present invention can be stored on such portable computer readable storage media and can be loaded onto persistent storage  405  via I/O interface(s)  406 . I/O interface(s)  406  also connect to display  409 . 
     Display  409  provides a mechanism to display data to a user and may be, for example, a computer monitor. 
     The present invention may be a system, a method, and/or a computer program product at any possible technical detail level of integration. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention. 
     The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire. 
     Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device. 
     Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, configuration data for integrated circuitry, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++, or the like, and procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention. 
     Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions. 
     These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions. 
     The programs described herein are identified based upon the application for which they are implemented in a specific embodiment of the invention. However, it should be appreciated that any particular program nomenclature herein is used merely for convenience, and thus the invention should not be limited to use solely in any specific application identified and/or implied by such nomenclature.