Electrical computers and digital processing systems: memory – Storage accessing and control – Hierarchical memories
Reexamination Certificate
1998-11-13
2001-06-19
Lim, Krisna (Department: 2153)
Electrical computers and digital processing systems: memory
Storage accessing and control
Hierarchical memories
C711S118000, C707S793000, C709S203000
Reexamination Certificate
active
06249844
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the analysis of the content of a digital document and in particular to the creation and maintenance of persistent fragment identities to facilitate caching.
BACKGROUND
With the rapid growth of the Internet, the need for efficient document exchange becomes increasingly important. In additional to the hypertext markup language (HTML), Extensible Markup Languages (XML) are becoming available that provide a meta-language for authors to design their own markup language.
On the other hand, the proliferation of various non-PC computing devices, including: handheld devices; palmtop devices; and various other Microsoft WINDOWS CE ™- based devices; set-top boxes; WEB TV; smart phones; and so-called Internet appliances, (hereinafter all referred to as Internet appliances) further complicates the presentation of a Web document to a client device. In a Web document based on HTML, images are treated as separate objects pointed to by the Web document. A proxy/Web server may generate a lower resolution version or a black and white version of a color image to accommodate the limited capability of the Internet appliance. Nonetheless, these images are named persistent objects (i.e., they have separate identities which are their URLs). The proxy or Web server is merely trying to provide different versions of a named entity based on the capability of a receiving device. This is independent of any caching issues at the proxy or Web server to improve object access time.
Various work exists to provide different versions of a named object in the Web environment to support Internet appliances access to the Web. For example, PRISM from Spyglass (see e.g., http://www.spyglass.com) provides different versions of images to the Internet appliance. It can also dynamically translate richly formatted Web documents into simplified Web pages to accommodate the requirements of the receiving devices. A means for performing on-demand data type-specific lossy compression on semantically typed data and tailoring content to the specific constraints of the clients is described in “Adapting to Newark and Client Variability via On-Demand Dynamic Distillation,” by A. Fox, et al., Proc. 7th Intl. Conference on Architectural Support for Programming Languages and Operating Systems, Oct. 1996.
Using formal descriptors, such as a markup language, to describe a digital document provides tremendous flexibility. In the Internet environment, more powerful markup languages such as XML, or a subset of the Standard Generalized Markup Language (SGML) (see e.g., ISO 8879/1986; and Designing XML Internet Applications, by M. Leventhal, et al., Prentice Hall, 1998), are being defined to augment HTML. The markup language description can provide rich information on the document structure and the final document to be generated. In fact, XML is a language that allows users to define their own language. For example, chemists can define a chemical markup language to describe a molecular structure. Mathematicians or scientists can define a math markup language to describe complex mathematical formulas. The interpretation of the markup language description and generation of the object can thus be complex. It is desirable to avoid regeneration of the same description repeatedly. Since Web pages, objects or documents on a common subject, or from the same company/division/department or authors often have parts in common, there is a need to go beyond recognizing just the repeated references to named entities (i.e., subject already has a name, e.g., URL) to subparts of named entities.
However, proxy or Web servers and client browsers today do not interpret the markup language to decompose a document or object into components, provide persistent identities and tracking mechanisms to facilitate caching and recognition of repeated occurrences of components of a named object. They mainly provide caching or processing service for named objects as a whole. For example, as mentioned previously, in HTML the text documents and images (which are separated out from the text documents by the authors) are all named objects and hence cacheable entities. Another problem is that if a document includes dynamic content caching is not meaningful as the next reference to the same document URL can result in a different version of the document. Thus a document is not cached even if only a small fraction of its content is dynamic. This is an issue for HTML documents today and is expected to become more severe for XML documents, which are more flexible and make it easier to incorporate various types of dynamic information, such as data from a database.
Thus, the need remains for a system and method for identifying and creating one or more persistent object fragments from named object, for example to facilitate caching. The present invention addresses this need.
SUMMARY
In accordance with the aforementioned needs, the present invention is directed to a method and apparatus for identifying and creating persistent object fragments from a named object. In one example, the present invention is directed to a method and apparatus for dynamically parsing a digital content description of a named digital object, creating and maintaining fragment identities to facilitate caching. Examples of named digital objects include but are not limited to: Web pages described in XML, SGML, and HTML.
The present invention has features which can parse/analyze the object description, identify object fragments and create persistent object fragment identities, and revise the object description by replacing each object fragment with its newly created persistent identity and send the revised object description to the requesting node. Depending upon the properties of a fragment, this can either enable the fragment to be cacheable (which can be at the content/proxy server and the client device in the Web environment), or make the revised object description cacheable at the server and client device. For example, consider the object description of a purchase order which contains a dynamic part to retrieve the current price of a product from the database. This dynamic part may be a small portion of the purchase order, but would prevent the object from being cached. According to one feature of the present invention for recognizing and treating the dynamic part as a separate fragment from the object description, the revised document becomes static and therefore cacheable. Furthermore, fragments can be nested.
A method is also provided to determine which part/segment of a named object to recognize as a fragment identity, based on its properties, which can include its size, processing cost to generate that segment of the object from its description, and other properties such as static vs. dynamic.
The present invention has yet other features to determine which fragments to cache and replace. The cache manager takes into account the fragment size and processing cost to generate the fragment.
The present invention has still other features which allow different versions to be generated for a fragment upon request. The version created can be determined by the property of the requesting devices and the fragment description. Different generators can be maintained for each type of descriptors or markup tags to generate different versions for different types of devices.
An example of a method for identifying object fragments in an object having features of the present invention comprises the steps of: analyzing an object description to identify one or more persistent object fragments associated with the object; creating the one or more persistent object fragments, in response to said analyzing; and creating a persistent object fragment identity for a persistent object fragment, based on one or more of formal descriptors or an object fragment property. In one embodiment the object description is revised by replacing at least one object fragment with an associated persistent object fragment identity to enable the fragment to be cacheable at one or more of a
Schloss Robert Jeffrey
Yu Philip Shi-Lung
International Business Machines - Corporation
Lim Krisna
Zarick Gail H.
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