Data processing: structural design – modeling – simulation – and em – Electrical analog simulator
Reexamination Certificate
2000-12-21
2003-11-11
Mizrahi, Diane D. (Department: 2175)
Data processing: structural design, modeling, simulation, and em
Electrical analog simulator
C703S007000
Reexamination Certificate
active
06647360
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to computing that utilise databases. It relates particularly to the scrolling of result sets of database information.
BACKGROUND OF THE INVENTION
In modern large computing systems a common topology has three tiers: (i) a presentation tier characterised by multiple workstations focusing on user interactions, (ii) a business tier characterised by multiple servers executing application/business logic, and (iii) a data tier characterised by multiple databases working on data storage and organization. A Local or Wide Area Network (LAN/WAN) interconnects the three tier elements.
Such computing systems find application in many and varied fields, ranging from university research and teaching facilities to business applications. In fact, almost every business will utilise such a system to transact its functions and serve its clients. For example, a system may be used to control inventory, for word processing and accounts purposes, and for servicing client's enquiries. Many businesses have very large client bases and may provide an extensive inventory of goods and services. One illustrative example is a telecommunications service provider (Telco) that serves a countrywide client base. The Telco's subscribers thus can number in the millions, and each customer will expect an immediate response from a Customer Service Representative (CSR) to any inquiry, which can range from billing information, a request for a new service, or the placing of orders for a product.
Similar examples are seen in Utilities, insurance companies, banks, hospitals, law firms, accountancy firms, stock exchanges, universities and Government agencies, to name but a few.
The CSR workstations may be external users who have network connections to the database servers. For example, a customer may be using a web browser connected to a vendor's web server via the Internet to access information stored in the vendor's database.
In almost all computer applications there are many situations where a user is viewing a subset of a large list of data, for example a Telco CSR viewing the billing information for a client. In these cases some form of scrolling will need to be implemented. In computer terms, scrolling is the ability to move (text) from right to left or up and down on a screen in order to view text that cannot be contained within a single display image.
When one considers a user viewing a subset of a large list in a graphical user interface (GUI) window with a scroll bar, the host application must respond to the following requests: First, Last, Next, Previous, and Search. ‘First’ positions the GUI window over the first subset of the list. ‘Last’ displays the final subset of the list. Given that the GUI window is displaying a subset of the list, ‘Next’ displays the next subset, and ‘Previous’ displays the previous subset. The ‘Search’ request gives the user the ability to find specific data within the list.
In client-server systems there are many problems associated with storing the potentially huge list of data on the server machine while the user (client) is scrolling over it. For example:
1. The server machine may run out of resources because it is holding result sets for many clients.
2. The server machine has to know when the client has finished.
3. If the client machine has crashed, and some form of ‘pinging’ is attempted to solve this, does the server have access to the client (e.g. if the client machine is behind a “firewall”)? If time-outs are used, what should the time-out be set to? Can the server be brought down by simply initiating many queries resulting in large scrolling lists during the time-out period? (Note also, that it is usually not acceptable to solve this by maintaining a (socket) connection between a client and server over a WAN due to a lack of network reliability.)
4. In many larger systems, and in Internet web server-based applications particularly, the server side of the application is implemented in such a way that client information cannot be held between transactions to allow greater throughput and prohibit resource over-use. In these systems, the data cannot be held between the scrolling requests.
There are also problems associated with transmitting the list to the client and storing it there. For example:
1. The list may be huge, and transmitting it would be unacceptably slow or impossible. In Internet-based applications, often the client is using a modem. Typical modem speeds are in the order of a few kilobytes of data per second. The list may easily be in the order of megabytes, or tens of megabytes, resulting in uselessly slow transfer. Some clients may have reliable and fast connections to the servers, while others have unreliable or slow connections.
2. The user must wait for transmission of the entire list before any of it can be displayed. If the application matches the user requirements well, typically the first window of data will be the most important and although access to the rest of the list may be required, it is often accessed much less frequently than the first window.
3. Storage must be reserved on the client machine for the list.
A specific known scolling arrangement is disclosed in published Japanese Patent Application No. 06-314306 (Hitachi Ltd, Takashi and Michiko), entitled: Data Base Display Method. This reference describes the workstation receiving a retrieved result set and storing it in a local file, then performing an extraction of the local file to display a portion of the data. This method suffers all the problems associated with transmitting the list to the client described above.
It is an object of the present invention to enable scrolling of data base result sets without incurring the problems associated with the prior art.
SUMMARY OF THE INVENTION
The invention provides a method for scrolling database records, comprising the steps of
(a) allocating a unique identifier to each database record;
(b) determining an upper context token and a lower context token corresponding to the end records for a subset of said records, the upper and lower context tokens including at least said identifier for the respective record; and
(c) for a scrolling request, utilizing the relevant upper or lower context token to locate an adjacent subset of said records
The invention further provides a method for scrolling database records on a client-server system where a database holds records, accessible by said server, that each includes a unique identifier, the method comprising the steps of:
(a) retrieving a set of said database records;
(b) the server determining an upper context token and a lower context token corresponding to the end records for a subset of said records, the upper and lower context tokens including at least said identifier for the respective record; and
(c) on a scrolling request by said client, the server utilizing the relevant upper or lower context token to locate an adjacent subset of said retrieved records;
(d) determining new upper and lower context tokens for said adjacent subset of records; and
(e) returning said subset to said client, together with said new context tokens.
Scrolling requests can include a next subset commencing from a lower context token, or a previous subset commencing from an upper context token. The scrolling requests further can include an additional statement in the search string that has predicates that include a reference to the unique identifiers. A search order statement can further be included in the scrolling request search string, the statement constituting the upper and lower context tokens, and including the references.
The invention yet further provides a client-server computing system providing scrolling of database records, comprising:
(a) one or more client computers running an application program that permits scrolling requests of data;
(b) a server computer, also running said client application program, and in communication with said clients by a communications link; and
(c) a database holding a store of records, accessible by sai
Dunwoody James Leonard
Graham Stephen Thomas
Ramsay Nigel James
Spence John Stanley
Drumheller Ronald L.
International Business Machines - Corporation
Mizrahi Diane D.
Wu Yicun
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