Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
2000-02-24
2004-08-03
Amsbury, Wayne (Department: 2171)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000
Reexamination Certificate
active
06772159
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the replication of a data subset of server data for use on a client device while the client device is disconnected from the server. In particular, the invention relates to methods for providing the data subset to the client device, and rendering the data subset on the client device using a generic data renderer.
BACKGROUND OF THE INVENTION
Each day, enterprises as small as the corner shoe store and as large as multinational congomerates generate new data and access existing data that are vital to the ongoing viability of the enterprise. Technology advances in hardware and software have made it possible to amass and manage large amounts of data. All aspects of an organization's activities are captured and stored in databases. Examples of such activities include sales, service, product development, advertising, personnel, benefits, education, and research. Storing data on computer systems makes it easier to gather the data, query and access the data, and to automate processes that use the data.
The enterprise data are maintained on computer systems called data servers, hereinafter, referred to as servers. Large servers are maintained by a professional staff and are housed in physically secure places. Smaller servers may be under the control of individuals and small groups and may be located in places like offices and laboratories.
Servers are located on computer networks and users access the data on the server from access points on the network. Users access the server over the network through the use of a client device (computer) which may have a permanent access point, like a desktop computer with a network interface, or a temporary access point, like a dial-up link to a network interface service. Using computer networks, it is just as easy to access a data server located down the hall as it is to access a data server located half way around the world.
There are various types of databases used by data servers. One type of database is referred to as a relational database. The relational database approach was introduced by E. F. Codd, in “A Relational Model for Large Shared Data Banks”, Communications of ACM, 13:6, pp. 377-387, 1970. A contemporary example of a relational database is IBM's DB2.
The relational database model offers programmers a simplified view of data. The basic unit of organizing the data is a database table. A database table is two-dimensional array. Each row is a database record, or a logical collection of data. The columns represent fields in a record. There has evolved a rich set of query APIs called the Structured Query Language (SQL), which can be used to query and manipulate the rows (records) and columns (fields of a record) of a database table. It is even possible to form relations on multiple tables.
Relational DBMS (database management systems) record information necessary for operation in a group of system-supplied tables referred to as a “catalog”. The catalog stores information about the data the DBMS is managing, which is referred to as “meta” data. For example, a catalog records the names of tables stored within a DBMS, the names of the users who have been granted access to the tables, and other data. The database meta data is created within the database system and is used extensively by the database system administrators. Database programmers are given limited programming access to some of the data. For example, the data types of columns in a table can be obtained. Relational database management systems are described further by Bontempo et al., in Database Management Principles and Products, Prentice Hall, 1995.
A relational database system is a simplified form of a general multi-level data system. In a relational database system, fields are the elements of rows, rows are the elements of the tables, and tables are the elements of the database system. However, another type of database referred to as an object database can have arbitrary levels since objects can be embedded in objects. At each level, the permissible operations are defined as a part of the object. An object database is a more general example of a multi-level data system.
There are two modes in which client devices use server data. In the first mode, the client remains connected to the server for the entire time the client is accessing and using server data. There are a number of techniques for optimizing the performance in this mode. Examples include data caching at the client, prefetching data, and replicating data at the client. An important point about this mode is that if, at a certain step in the computation, the client needs data from the server in order to proceed in the computation, the client merely needs to issue a data fetch request to the server.
In the second mode, the client uses the data while disconnected from the server. First, the client must specify and fetch all of the data needed for use during the period of disconnection. This is called hoarding. Next, the client disconnects from the server. During the period of disconnection, the user may use the data on the client in a variety of ways. These include creating new data elements, modifying the data, and referencing the data. Lastly, the client must at some point connect to the server to perform synchronization. This action integrates the client replica of the data with the server data. The first access mode and the second mode are hereinafter referred to as connected data access mode as disconnected data access mode, respectively.
Disconnected data access is becoming an increasingly important mode of access. Many industries employ mobile workers who perform a significant part of their work away from the office. Examples include insurance agents, visiting nurses, and field service technicians. Corporations are re-engineering their work processes to put workers in the field and on the factory floor where they respond much faster to customer and corporate needs. As the population of the mobile work force rapidly grows, it is becoming increasingly important for enterprises to extend information and applications to their mobile workers.
When this trend first started, the client device of choice was a notebook computer running a WINDOWS operating system. One advantage of this client device was that it was basically the same software environment as that employed on the user's desktop or office computer. Since the software environment was similar, it was easy for the user to go between using applications and data in connected mode in the office and using the applications and the data in disconnected mode on the notebook.
New client device types are constantly emerging. Handheld computers, personal digital assistants (PDAs), smart phones, and clam shell notebooks are some of the new client devices that are available today. When compared to standard notebook computers, these new devices have a smaller form factor, a lower cost of ownership, and are easier to use. All of these factors are leading to rapid acceptance of these devices as client devices by mobile workers.
These new client devices have significantly less resources than notebook computers or desktop personal computers (PCs). Currently, the total amount of memory,and storage on some of these devices is less than 10 Megabytes. On desktop PCs, total memory and storage can easily exceed gigabytes. The display size on some of these new client devices is less than 2 inches by 2 inches. The operating systems on the new client devices are all different from the operating system on desktop PCs. As a result of these factors, desktop PC application generally cannot be directly ported to handheld computers, cell phones, or PDAs.
Given the variety of device types and the different brands within a device type, users will use a diverse set of device types as client devices. Even when the information system staff of an enterprise has the authority to impose device usage, it will not be in their best interests to do so.
A description of the prior and current state of the art in connected and disconnecte
Blount Marion L.
Lei Hui
Tait Carl D.
Amsbury Wayne
F. Chau & Associates LLC
Nguyen Cindy
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