Data processing system and method for accessing files

Details Data processing system and method for accessing files Data processing system and method for accessing files

1997-11-21

2004-10-05

Pardo, Thuy N. (Department: 2175)

Data processing: database and file management or data structures

Database design

Data structure types

C707S793000, C707S793000, C707S793000

Reexamination Certificate

active

06801911

ABSTRACT:

TECHNICAL FIELD
The present invention relates in general to a file system in a communication network, and more particularly, to the use of uniform resource locators to access the file system in the communication network.
BACKGROUND INFORMATION
Various file systems are currently implemented for data processing systems in a variety of networks. Most users are familiar with a methodology for accessing a file in a file system implemented on their personal computer (PC). When accessing that file, the user opens the file, reads or writes from the file, and then closes the file. To open the file to communicate information thereto, the user must first specify the name of the file. Generally, for personal computers, the file name is specified in a file system open call where one of the arguments is the name of the file in the form of a character string:
a:\pathname\filename
In the call provided above, the “a” indicates a drive in which the file is located. The “pathname” indicates a name of a folder or directory in which the file is located and the “filename” is a name of the file itself.
When a central processing unit (CPU) in a PC receives such a name, the central processing unit first accesses the drive, and locates a folder directory specified by the pathname. Subsequently, the CPU searches the folder or directory for the file corresponding to the filename specified in the user's call.
When a programmer desires to use a file or device, the programmer passes the name of that file or device as a parameter to an “open” call along with possible other parameters. The other parameters may, for example, indicate what kind of sharing may be permissible. Files, in general, are specified using “path names”. For example, an open call with the name:
a:\dir
1
\dir
2
\filename.ext,
specifies that the file is on drive “a,” with the filename being “filename.ext” in directory “dir
2
,” in directory “dir
1
,” of the root of drive “a”. Devices often use reserved file names such as: LPT
1
for Printer
1
; COM
1
for Serial Communications Port
1
; and CON for the console keyboard and display, among others.
The “open” call locates the file on the hard drive or other device and creates a data structure in memory, usually called a “file control block” which contains detailed information about the physical location of the file or device specified, as well as information such as the current position in the file when the file is being read sequentially.
The operating system returns a “handle” from the open call and the handle is then used to locate the file control block for use on future “calls.” These future calls include reading/writing from/to the file or device. For example a “read” call would typically have four parameters: a handle, a location of data buffer into which to place the read data, the size of this buffer, and a place to store the amount of data actually written into the data buffer. Similarly, a “write” call would typically have the following four parameters: a handle, the location of the data buffer containing the data to be written, the number of bytes to be written, and a place to store the amount of data actually written (in case not all of the requested bytes to be written are written because the media is full). Additionally, there may be several other related calls such as those for setting the position of the next read or write operation in the file specified by the handle, and perhaps some special “calls” set forth when additional functions may be possible for a given file or device. Such special calls may include ejecting a CD or rewinding a tape.
Finally, when the program has finished using the file or device specified by the handle, a “close” call is made to deallocate the file control block and any other operating system buffers that may have been allocated to process the input/output activity for the file.
As users became more comfortable with personal computers and with the techniques used to access data therein, including the previously described file access techniques, use of personal computers became increasingly common place. Today, a worldwide network of computers exists to allow users on different personal computers to communicate with one another. Indeed, the worldwide network of computers, commonly known as the “Internet,” has seen explosive growth in the last several years. This growth has been typically fueled by the introduction and widespread use of “web” browsers that allow for simple graphical user interface-based access to network servers. Such network servers typically support documents formatted as “web pages.” The “World Wide Web” (www) is a collection of servers on the Internet that utilize the Hypertext Transfer Protocol (HTTP), a known application protocol that provides users access to files using a standard page description language referred to as HyperText Markup Language (HTML). It should be noted that files may be provided in different formats such as text, graphics, images, sound, and video, among others. HTML provides basic document formatting and allows a developer to specify “links” to other servers and files. Use of an HTML-compliant client browser involves specification of a link via a Uniform Resource Locator, commonly known by the acronym, “URL.” Upon specification of a URL, a client may make a TCP/IP (Transmission Control Protocol/Internet Protocol) request to the server identified in the link and receive a “web page” in return, where the “web page” is a document formatted according to HTML.
It should be noted that the Internet typically includes a large network of web sites that are accessible by clients, wherein the client is typically a user and his personal computer. Clients may access the Internet through a private Internet access provider, an on-line service provider, or a personal access or service provider. It should be noted that such access providers and service providers will hereinafter be collectively referred to as “web servers.” Additionally, it should be noted that web servers may also be found at web sites. Each site selectively operates a “web site” that supports files in the form of documents or pages.
A network path to a server is identified by a URL having a known syntax for defining a network connection. This URL typically has the form of:
http://domain name/directory path/filename.
It should be noted that “http” identifies a type of Internet protocol used for storage and transmission of information. Alternatives to an HTTP format include Gopher, Telnet, FTP (File Transfer Protocol), and Usenet News. Furthermore, it should be noted that a URL occasionally includes a port number that is placed directly after the domain name. Such URLs provide a consistent, easily understood method of addressing different files of data at Internet or World Wide Web sites.
When the client receives an URL having one of the aforementioned forms, a central processing unit within the client must open a connection to the server using the TCP/IP protocol. A first step in opening this communication requires the central processing unit to open a “socket.” Sockets (aka Berkeley Sockets, or Winsock) is an application programming interface (API) commonly used to access the Internet. Generally, to “open a socket” the next three steps are taken. A socket is first allocated. Next, a socket is “bound” to a local address that identifies the client. The socket is then “connected” to a remote host, usually a server. Data is “received” and “sent” (using receive and send calls) between the client and host as needed according to HTTP, FTP . . . or another communication protocol. The communication protocol establishes the format of the request data that is sent to the server and the format of returned data. Finally, a socket is “closed”.
API's other than “sockets” are available for accessing the Internet such as TLI, XTI and others at various levels in a communication stack of software. However, regardless of the communication protocol used, the basic principles remain the same and may be used to implement alternate embodime

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