Method and system for caching presentation data

Details Method and system for caching presentation data Method and system for caching presentation data

1999-12-14

2004-03-16

Maung, Zarni (Department: 2154)

Electrical computers and digital processing systems: multicomput

Computer-to-computer data routing

Least weight routing

C709S216000, C711S118000

Reexamination Certificate

active

06708196

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to a computer method and system for caching presentation data and, more specifically, to a method and system for retrieving and maintaining multiple entries of presentation data in a presentation cache.
BACKGROUND OF THE INVENTION
Some computer system environments allow data from one application to be integrated with data from another application in such a way that all of the data appears to a user to be managed by one application. The data belonging to the application providing a containment environment for all of the data is typically referred to as native data. The containment environment is typically referred to as a container and the application responsible for providing and managing the container is typically referred to as a container application or container program. The data being incorporated into the native data that is generated by and managed using another application is typically referred to as non-native data. Users can embed non-native data within the native data of a container application by inserting the non-native data into the storage structure of the container application. Or, users can link non-native data into the native data of a container application by storing an indicator to the non-native data in the storage facilities of the container application. When embedded or linked, such non-native data is referred to as source data and the program used to manipulate the source data is referred to as the server program. Consequently, the container program is also referred to as a client program because it is a client of the source data maintained by the server program.
For example, a user may wish to create a document using a word processing application containing a chart created by a spreadsheet application. Such a document is sometimes referred to as a compound document.
FIG. 1
is an example of a compound document. In this example, the compound document
101
is generated as a report for a certain manufacturing project. The compound document
101
contains scheduling data
102
, which is presented in chart format; budgeting data
103
, which is presented in spreadsheet format; and explanatory data
104
, which is presented in text format. In typical prior systems, a user generates the scheduling data
102
and the budgeting data
103
using a spreadsheet computer program. After this data has been generated, the user creates the compound document
101
, enters the explanatory data
104
, and incorporates the scheduling data
102
and budgeting data
103
using a word processing computer program. In this example, the explanatory data
104
is native data to the word processing computer program, and the scheduling data
102
and budgeting data
103
is non-native data (source data) contained within a compound document (a container).
Within an environment such as that shown in
FIG. 1
, where the linking or embedding of non-native data is supported, often times the container program desires to display the non-native data as well as the native data. However, the container program (the client program) does not understand the non-native data because it was created by and is managed by the server program. Thus, in prior systems that use conventional architectures, the non-native data is typically stored by the client program in a presentation format so that it can be displayed by the client program. A presentation format is a format in which the data can be easily displayed on an output device. For example, the presentation format may be a bitmap that can be displayed with a standard bitmap block transfer operation (BITBLT). (For example, in
FIG. 1
the scheduling data
102
and budgeting data
103
may be stored by the word processing program as bitmaps, or in other formats, when they are embedded in compound document
101
.) Alternatively, if the non-native data is linked by the client program, then the client program typically stores a link to the source data that has been formatted in a format that the client program can treat as a presentation format. In these prior systems, when the client program wishes to display the non-native data using conventional programming style, it renders (places appropriately on a particular output device) the non-native data stored according to the presentation format. Data stored according to a presentation format is sometimes referred to as presentation data.
If the client program desires to display the non-native data in a format different from that which it has stored (or has access to via a link), then the client program can request the data again from the server program but in a different presentation format. For example, a client program may wish the data in another presentation format to print the native and non-native data together in a paginated format. The client program can then render the data in the new presentation format received from the server program. Requesting the data again from the server program requires the server program to be reloaded and re-executed.
Also, in prior systems that support an object-oriented environment, if the non-native data belongs to an object (objects are discussed further below), then the client program typically invokes a function member of the object requesting the object to draw itself in a particular location or context. Note that this latter technique gives the client program little control over how the object renders the object's data.
The present invention is described below using some object-oriented techniques; thus, an overview of well-known object-oriented programming techniques is provided. Two common characteristics of object-oriented programming languages are (1) support for data encapsulation and (2) data type inheritance. Data encapsulation refers to the binding of functions and data. Inheritance refers to the ability to declare a data type in terms of other data types. In the C++ language, data encapsulation and inheritance are supported through the use of classes. A class is a user-defined type. A class declaration describes the data members and function members of the class. A function member is also referred to as a method of a class. The data members and function members of a class are bound together in that the function operates on an instance of the class. An instance of a class is also called an object of the class. Thus, a class provides a definition for a group of objects with similar properties and common behavior.
To allocate storage for an object of a particular type (class), an object is instantiated. Once instantiated, data can be assigned to the data members of the particular object. Also, once instantiated, the function members of the particular object can be invoked to access and manipulate the data members. Thus, in this manner, the function members implement the behavior of the object, and the object provides a structure for encapsulating data and behavior into a single entity.
To support the concept of inheritance, classes may be derived from (based upon the declaration of) other classes. A derived class is a class that inherits the characteristics—data members and function members—of its base classes. A class that inherits the characteristics of another class is a derived class. A class that does not inherit the characteristics of another class is a primary (root) class. A class whose characteristics are inherited by another class is a base class. A derived class may inherit the characteristics of several classes; that is, a derived class may have several base classes. This is referred to as multiple inheritance.
A class may also specify whether its function members are virtual. Declaring that a function member is virtual means that the function can be overridden by a function of the same name and type in a derived class. If a virtual function is declared without providing an implementation, then it is referred to as a pure virtual function. A pure virtual function is a virtual function declared with the pure specifier, “=0”. If a class specifies a pure virtual function, t

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