Document requesting system and method of receiving related document in advance

The degree of association between each document specified by each of the URLs included in the document transferred from a document providing system to a document requesting system and the document specified by the preceding document request is determined on the basis of the depth of link between the document specified by the preceding document request and each document specified by each URL or the degree of similarity between the contents of those documents. Using the thus obtained degree of association, a document to be received in advance is specified in the document requesting system. Consequently, even when a document having a lot of URLs is requested first or when each of the documents requested as related documents further includes a URL specifying another document, the document requesting system can specify documents closely related to the first requested document.

BACKGROUND OF THE INVENTION 
The present invention relates to a document requesting system that requests 
a document providing system to transfer a document, and more particularly 
to a document requesting system that receives not only the requested 
document but also related documents in advance from a document providing 
system. 
In recent years, the WWW (World Wide Web) has been widely known as a system 
that causes servers to provide various types of electronic information to 
clients through a network. The system, as shown in FIG. 1, comprises a WWW 
server 11 and a WWW client 12, for example. The server 11 provides 
document information to the client 12 via communication sections 21, 22 
according to a predetermined file transfer protocol HTTP (HyperText 
Transfer Protocol) between the server 11 and the client 12. The spread of 
the WWW enables access to document information all over the world through 
the network. 
In the system, the transfer of document files from a server to a client is 
basically carried out one by one. Specifically, when the user requires the 
display of a document, the WWW client communicates with the WWW server, 
which transfers the document to the WWW client, which then displays the 
document on the screen. To display another document, the same operation is 
performed again. Thus, WWW is based on the assumption that it is used only 
on-line. 
Accordingly, to acquire information through WWW using a portable data 
terminal, such as a notebook computer or a PDA (Personal Digital 
Assistance), the portable data terminal must be connected to the network 
until the use of WWW is finished. Since such a portable data terminal is 
not always used under the conditions where it can be constantly connected 
to the network, it is needed to automatically download as much information 
as possible all at once into the portable data terminal during the 
connection to the network so that the contents of the information can be 
read even after the disconnection from the network. 
One method of realizing this is a method of causing the server to transfer 
not only the document the user has requested to be transferred but also 
related documents to the client. 
This approach enables the user to cause the server to transfer a plurality 
of documents to the client by one instruction without directing the 
transfer of each document. The transferred documents are stored in the 
client's storage medium. Specifically, the approach is based on a method 
of starting a program that transfers a plurality of documents according to 
a transfer request made by the user and storing them in the client's 
storage medium or a method of concatenating a plurality of documents into 
a single document in advance and storing the concatenated document in the 
client's storage medium. The approach, however, has the following problem. 
When a document is requested, documents determined to be related documents 
must be determined beforehand on the server side. This requires the 
process of preparing a document list indicating related documents on the 
server side and sending the list to the client. 
Consequently, a judgment as to which documents are related documents is 
entirely up to the document provider and therefore related documents 
cannot be specified on the client side. 
BRIEF SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a document 
requesting system that enables the client side to specify documents to be 
received in advance as related documents and is capable of receiving 
suitable related documents in advance only with the functions of the 
client and a method of receiving related documents in advance. 
According to one aspect of the present invention, there is provided a 
document requesting system for requesting the transfer of related 
documents to be received in advance, comprising: means for extracting from 
a first document transferred by request an identifier specifying a second 
document linked to the first document; and means for determining the 
degree of association between the second document specified by the 
extracted identifier and a predetermined document as a reference, the 
second document being determined to be one of the related documents in the 
case where the degree of association is larger than a specific degree of 
association. 
According to another aspect of the present invention, there is provided a 
client unit for requesting a server unit to transfer of related documents 
to be received in advance which are written in HTML (HyperText Markup 
Language) form, comprising: means for extracting from a first document 
transferred by request from the server unit a URL (Uniform Resource 
Locator) an identifier specifying a second document linked to the first 
document; and means for determining the degree of association between the 
second document specified by the extracted URL and a predetermined 
document as a reference, the second document being determined to be one of 
the related documents in the case where the degree of association is 
larger than a specific degree of association. 
According to another aspect of the present invention, there is provided a 
document requesting system for requesting the transfer of related 
documents to be received in advance, comprising: means for extracting from 
a first document transferred by request an identifier specifying a second 
document linked to the first document; means for determining the depth of 
link between the second document specified by the extracted identifier and 
a predetermined document as a reference, the second document being 
determined to be one of the related documents in the case where the depth 
of link is smaller than a specific value; and means for requesting the 
transfer of the second document in the case where the depth of link is 
smaller than the specific value. 
In this system, the determining means may include a number-of-levels 
counter which counts the number of levels that indicates what level of 
hierarchy the second document falls from the predetermined document as the 
reference. In this case, the second document is determined to be one of 
the related documents in the case where the number of levels indicated by 
the number-of-levels counter is smaller than a specific value. 
According to another aspect of the present invention, there is provided a 
document requesting system for requesting the transfer of related 
documents to be received in advance, comprising: means for extracting from 
a first document transferred by request an identifier specifying a second 
document linked to the first document; means for requesting the transfer 
of the second document specified by the extracted identifier; and means 
for determining the degree of similarity between the second document 
transferred by request and a predetermined document as a reference, the 
second document being determined to be one of the related documents in the 
case where the degree of similarity is larger than a specific value. 
In this system, the determining means may include means for calculating the 
percentage of common or similar words between the second document and the 
predetermined document as the reference. In this case, the second document 
is determined to be one of the related documents in the case where the 
percentage indicated by the calculating means is larger than a specific 
value. 
According to another aspect of the present invention, there is provided a 
method of receiving related documents in advance for use in a document 
requesting system for requesting the transfer of the related documents, 
the method comprising the steps of: extracting from a first document 
transferred by request an identifier specifying a second document linked 
to the first document; and determining the degree of association between 
the second document specified by the extracted identifier and a 
predetermined document as a reference, the second document being 
determined to be one of the related documents in the case where the degree 
of association is larger than a specific degree of association. 
According to another aspect of the present invention, there is provided a 
method of receiving related documents in advance which are written in HTML 
(HyperText Markup Language) form, for use in a document requesting system 
for requesting the transfer of the related documents, the method 
comprising the steps of: extracting from a first document transferred by 
request from the server unit a URL (Uniform Resource Locator) an 
identifier specifying a second document linked to the first document; and 
determining the degree of association between the second document 
specified by the extracted URL and a predetermined document as a 
reference, the second document being determined to be one of the related 
documents in the case where the degree of association is larger than a 
specific degree of association. 
According to another aspect of the present invention, there is provided a 
method of receiving related documents in advance for use in a document 
requesting system for requesting the transfer of the related documents, 
the method comprising the steps of: extracting from a first document 
transferred by request an identifier specifying a second document linked 
to the first document; determining the depth of link between the second 
document specified by the extracted identifier and a predetermined 
document as a reference, the second document being determined to be one of 
the related documents in the case where the depth of link is smaller than 
a specific value; and requesting the transfer of the second document in 
the case where the depth of link is smaller than the specific value. 
In this method, the determining step may include the step of counting the 
number of levels that indicates what level of hierarchy the second 
document falls from the predetermined document as the reference. In this 
case, the second document is determined to be one of the related documents 
in the case where the number of levels indicated by the number-of-levels 
counter is smaller than a specific value. 
According to another aspect of the present invention, there is provided a 
method of receiving related documents in advance for use in a document 
requesting system for requesting the transfer of the related documents, 
the method comprising the steps of: extracting from a first document 
transferred by request an identifier specifying a second document linked 
to the first document; requesting the transfer of the second document 
specified by the extracted identifier; and determining the degree of 
similarity between the second document transferred by request and a 
predetermined document as a reference, the second document being 
determined to be one of the related documents in the case where the degree 
of similarity is larger than a specific value. 
In this method, the determining step may include the step of calculating 
the percentage of common or similar words between the second document and 
the predetermined document as the reference. In this case, the second 
document is determined to be one of the related documents in the case 
where the percentage obtained by the calculating step is larger than a 
specific value. 
Additional objects and advantages of the present invention will be set 
forth in the description which follows, and in part will be obvious from 
the description, or may be learned by practice of the present invention. 
The objects and advantages of the present invention may be realized and 
obtained by means of the instrumentalities and combinations particularly 
pointed out in the appended claims.

DETAILED DESCRIPTION OF THE INVENTION 
Before a detail explanation of an embodiment of the present invention, the 
basic idea of the invention will be briefed to make it easier to 
understand the invention. 
With this document requesting system, on the basis of the degree of 
association between the document specified by the identifier included in 
the transferred document and the first transferred document, it is judged 
whether or not the document specified by the identifier can be a related 
document to be received in advance. This enables the document requesting 
system side to specify a related document that can be received in advance. 
The degree of association can be determined on the basis of the depth of 
the link between the document specified by the first request and the 
document specified by the identifier or on the basis of the degree of 
similarity between the contents of documents. 
Therefore, even when a document with many identifiers is first requested or 
when the document requested as a related document further includes an 
identifier, the document requesting system side can specify any document 
closely related to the first requested one of the many documents specified 
by those identifiers. By use of WWW, this makes it possible to receive a 
suitable related document in advance using only the function of a browser 
acting as a WWW client without changes in a WWW server. 
Hereinafter, referring to the accompanying drawings, an embodiment of the 
present invention will be explained in detail. 
FIG. 2 shows a data communication system to which a file reading method 
according to the embodiment of the present invention is applied and the 
organization of the functions of programs used in the system. The data 
communication system is, for example, a client/server system that provides 
various document files (including HTML hypertext, still pictures, moving 
pictures, and voice), making use of a network environment, such as the 
Internet, and comprises a document providing system 110 which functions as 
a WWW server that provides document files and a document requesting system 
120 which functions as a WWW client that requests a document file. 
In the document providing system 110, a document providing program 150 
includes a request accepting section 151 and a request processing section 
152 is in operation. The request accepting section 151 accepts a request 
from a document display program 130 that is in operation in the document 
requesting system 120. The request processing section 152 performs 
concrete processes according to the request accepted at the request 
accepting section 151. For example, the request processing section 152 
searches a storage medium 156 for a document 111 corresponding to the 
request accepted at the request accepting section 151. If having found the 
corresponding document, it transmits the document to the document 
requesting system 120. Although not shown in FIG. 2, the requesting of a 
document and the transmission of a document between the document providing 
program 150 and the document display program 130 are carried out via 
communication sections 21, 22 in the form of hardware as shown in FIG. 1. 
In the document requesting system 120, the document display program 130 is 
in operation which includes a document requesting section 132, a document 
reception section 133, a document storage section 134, a document 
identifier extracting section 138, a condition judging section 139, a 
document display section 135, and a request accepting section 136. 
The document requesting section 132 requests the document providing system 
110 to provide a document. The document reception section 133 receives the 
document provided by the document providing system 110. 
The document storage section 134 stores the document received from the 
document providing system 110 into the storage medium 121. The document 
identifier extracting section 138 analyzes the document received at the 
document reception section 133 and extracts a document identifier. 
The condition judging section 139 is a program that judges whether or not 
the document corresponding to the identifier extracted at the document 
identifier extracting section 138 is a document file to be received in 
advance, on the basis of the degree of association (explained later) 
between the document specified by the identifier and the first requested 
document. 
The document display section 135 displays the requested document. The 
request accepting section 136 accepts a request. The document display 
program 130 is not necessarily a single program, but may be made up of 
more than one program. 
FIG. 3 shows a description of the requested document. In the example of 
FIG. 3, a document 200 is written in HTML form (HyperText Markup Language) 
and includes URLs (Uniform Resource Locators) 201, 202 as identifiers for 
identifying documents. A URL is an identifier for determining the location 
of a document uniquely and takes the form of 
"&lt;scheme&gt;:&lt;scheme-specific-part&gt;". For example, it is expressed as 
"http://www.toshiba.co.jp/index.html". In the description, "http" means 
that http is used as a protocol for transmission and 
"//www.toshiba.co.jp/index.html" indicates the file "index.htm" in the 
host "www.toshiba.co.jp". The document identifier extracting section 138 
in the document requesting system 120 extracts such URLs as 201 and 202 
from the received document 200. 
For reference, all the links including the link between the document 200 
and the documents 201, 202, are shown in FIG. 4. 
FIG. 5 shows the flow of the process of judging and requesting related 
documents in the document requesting system 120 associated with the 
present invention. 
In the document requesting system 120, the document requesting section 132 
requests a document (step S301). When the document reception section 133 
have received the document corresponding to the request (step S302), the 
document storage section 134 stores the document into the storage medium 
121 of the document requesting system 120 (step S303). Next, the document 
identifier extracting section 138 extracts a document identifier included 
in the document (step S304). 
Then, the document specified by the identifier extracted at the document 
identifier extracting section 138 is considered to be a related document. 
The condition judging section 139 judges whether to request the document 
from the document providing system 110 (step S305). Thereafter, a check is 
made to see if the judgment result from the condition judging section 139 
fulfills a predetermined condition (step S306). If it meets the condition, 
the document requesting section 132 will request the corresponding 
document from the document providing system 110 according to the 
identifier extracted at the document identifier extracting section 138. 
Next, an example of a concrete condition judging method used in the 
condition judging section 139 of the document display program 130 will be 
explained. 
As shown in FIG. 6, a number-of-levels counter 139c for counting the number 
of levels of hierarchy of a document is provided in part of a data storage 
section 139m provided in the condition judging section 139. Use of the 
number-of-levels counter 139c makes it possible to judge whether the level 
of hierarchy of the document at the link destination of a document is 
higher or lower than a specific level of hierarchy. If it is lower than 
the specific level of hierarchy, a document at the link destination is 
requested. The repetition of this process will enable the related 
documents to be received in advance. 
Specifically, the number-of-levels counter 139c presents the depth of the 
link of document A, when the first requested document K (the document that 
is currently searching for a related document) is used as a reference. For 
example, when URL indicating document A is included in the first requested 
document K, the value of the number-of-levels counter 139c is 1. In the 
example of FIG. 7, the documents corresponding to 201 and 202 are 
documents one level higher in hierarchy than document 200 and their number 
of levels is 1. If the document corresponding to 202 includes a URL, the 
number of levels of the document corresponding to the URL will be 2. For 
instance, if the maximum number of levels is set at 2, a document for 
which the value of the number-of-levels counter 139c is 2 will be called, 
but a document for which the value of the number-of-levels counter 139c is 
3 will be not called. 
FIG. 8 is a flowchart for a condition judging method used in the condition 
judging section 139 of the document display program 130. 
In this example, as a method of specifying related documents, the processes 
are repeatedly carried out in which each of URLs included in a document 
transmitted in response to a document request is searched and another 
request for a document corresponding to the URL is transferred to the 
providing system 110. Note that the search for URLs in each of the 
documents may be recursively executed. 
The flowchart of FIG. 8 shows the flow starting from when the document 
requesting section 132 requests a document. The process at the condition 
judging section 139 corresponds to the processes at step S405 and later. 
In the document display program 130, the document requesting section 132 
requests a document (step S401). The document reception section 133 
receives the requested document (step S402). The document storage section 
134 stores the received document into the storage medium 121 of the 
document requesting system 120 (step S403) and thereafter the document 
identifier extracting section 138 extracts a URL from the received 
document A (step S404). 
Next, regarding document A, the condition judging section 139 of the 
document requesting system 120 judges the condition for specifying a 
related document as follows. 
As a result of URL extraction at the document identifier extracting section 
138, a check is made to see if any URL is included in document A (step 
S405). If a URL is included, the number-of-levels counter 139c is 
increased by one (step S406). 
Next, the value of the number-of-levels counter 139c is compared with the 
predetermined maximum number of levels of hierarchy (step S407). When the 
value of the number-of-levels counter 139c is larger than the maximum 
number of levels, the value of the number-of-levels counter 139c is 
decreased by one (step S410) and the processing of document A is ended. 
Then, the remaining processes from step S408 are performed on document K 
which is the parent of document A. 
When the result of comparison with document A at step S407 has shown that 
the value of the number-of-levels counter 139c is equal to or smaller than 
the maximum number of levels, the processes from step S401 are performed 
recursively on all of the URLs extracted at step S404 through the 
processes from step S408 explained later. By removing the already 
requested ones of the URLs extracted at step S404 from the objects to be 
processed, link loops can be dealt with. 
The processes from step S408 are as follows. A check is made to see if any 
of the URLs extracted at step S404 has not requested a corresponding 
document yet (step S408). If any of the URLs has not requested a document 
yet, one URL that has not requested a document is selected (step S409) and 
the processes at step 401 and later are performed on the URL. 
Specifically, at step S401, document B corresponding to the selected URL is 
requested. When a URL is included in document B at step S405 and the 
comparison at step S407 has shown that the value of the number-of-levels 
counter 139c is equal to or smaller than the maximum number of levels, the 
ones that have not required a document yet are taken out of the URLs 
extracted from document B at step S409. Then, the processes at step S401 
and later are performed on them. When it has been judged at step S405 that 
no URL is included in document B, the processing of document B will be 
terminated and a return is made to the processing of document A. When the 
value of the number-of-levels counter 139c is larger than the maximum 
value at step S407 or when all of the URLs extracted from document B have 
been processed at step S408, the value of the number-of-levels counter 
139c is decreased by one and the processing of document B is ended. Then, 
a return is made to the processing of document A. 
As described above, a judgment is made to specify the related documents by 
determining the depth of link between each of the documents specified by 
URLs and the first requested document, thereby making it possible to 
selectively receive only documents with high degree of association in 
advance. 
FIG. 9 is another flowchart for a condition judging method used in the 
condition judging section 139 of the document display program 130. 
In this example, as a method of specifying a related document, the degree 
of similarity between document A transmitted in response to a request for 
a document and its ancestor document (a specifying document having the URL 
that specifies document A, a document one step precedent to the specifying 
document, a document corresponding to the document K which has been first 
requested, or the like) is used. The flowchart of FIG. 9 shows the flow 
starting from when the document requesting section requests a document. 
The process of judging conditions corresponds to the processes at step 
S505 and later. 
In the document display program 130, the document requesting section 132 
requests a document (step S501). The document reception section 133 
receives the requested document (step S502). The document storage section 
134 stores the received document into the storage medium 121 of the 
document requesting unit 120 (step S503) and thereafter the document 
identifier extracting section 138 extracts a URL from the received 
document A (step S504). 
Next, regarding document A, the condition judging section 139 of the 
document requesting system 120 judges the conditions for specifying 
related documents as follows. 
As a result of URL extraction at the document identifier extracting section 
138, a check is made to see if any URL is included in document A (step 
S505). If a URL is included, the degree of similarity between document A 
and an ancestor document of document A is calculated (step S506) and the 
calculated degree of similarity is compared with a predetermined threshold 
value (step S507). 
When the degree of similarity calculated at step S506 is equal to or larger 
than the predetermined threshold value, that is, in the case where the 
document A is determined to be the related document, it is considered that 
all documents specified by the extracted URLs should be received in 
advance. In this case, a check is made to see if any of the URLs extracted 
at step S504 has not requested a document yet (step S508). 
If some of the URLs have not requested a document yet, one URL that has not 
requested a document yet is selected and a return is made to step S501, 
where a request is made for the document corresponding to the selected 
URL. Accordingly, when the calculated degree of similarity is equal to or 
larger than the predetermined threshold value, the processes at step S501, 
where a document is requested, and subsequent steps are performed 
recursively on the all of the URLs extracted at the document identifier 
extracting section 138. 
A concrete example of a method of calculating the degree of similarity in 
FIG. 9 will be described. 
As shown in FIG. 10, a common word-and-phrase percentage computing section 
139r is provided in the condition judging section 139. The common 
word-and-phrase percentage computing section 139r is provided to realize 
an approach for judging the degree of similarity and calculates the 
percentage of words common to documents. 
FIG. 11 is a flowchart for a method of calculating the degree of 
similarity. 
In the example, the degree of similarity is calculated using the groups of 
words appearing in the requested document A and the document B received 
immediately before document A and it is judged whether or not document A 
is a related document. The flowchart of FIG. 11 shows the flow starting 
from when the document requesting section requests a document. 
In the document display program 130, the document requesting section 132 
requests a document (step S601). The document reception section 133 
receives the requested document (step S602). The document storage section 
134 stores the received document into the storage medium 121 of the 
document requesting unit 120 (step S603). 
Next, a check is made to see if the received document A is equal to an 
ancestor document (step S604). If document A is different from an ancestor 
document, the document identifier extracting section 138 extracts a URL 
from the received document A (step S605). 
Next, regarding document A, the condition judging section 139 of the 
document requesting system 120 judges the conditions for specifying 
related documents as follows. 
As a result of URL extraction at step S605, a check is made to see if any 
URL is included in document A (step S606). If a URL is included, a word is 
extracted from document A (step S607). 
Next, a check is made to see if document A is the document K the user has 
requested (step S608). This is done by comparing the URL of document A 
with that of document K. If document A differs from document k, document A 
can be considered to be the document that the document requesting system 
120 has requested as a related document of document K. Therefore, it is 
judged whether or not the document corresponding to the URL included in 
document A is determined to be a related document of document K. 
Specifically, taking into account only a specific part of speech (a group 
of specific parts of speech), the common word-and-phrase percentage 
computing section 139r calculates the percentage of words in the part of 
speech (or the group of parts of speech) common to document A and document 
B which is the parent of document A (step S609). Next, the percentage of 
the common words in the part of speech (or the group of parts of speech) 
is compared with the predetermined threshold value (step S610). 
When the content by percentage of the common words in the part of speech 
(or the group of parts of speech) is equal to or larger than the threshold 
value, or when it is found at step S608 that document A is document K that 
the user has requested, a check is made to see if any of the URLs 
extracted at step S605 has not requested a document yet (step S611). 
If some of the URLs have not requested a document, one URL that has not 
requested a document yet is selected (step S612) and a return is made to 
step S601, where a request is made for the document corresponding to the 
selected URL. Accordingly, when the content by percentage of the common 
words in the part of speech (or the group of parts of speech) is equal to 
or larger than the threshold value, or when it is found that document A is 
document K that the user has requested, the processes at step S601 and 
later are performed recursively on the all of the URLs extracted at the 
document identifier extracting section 138. 
Some of documents provided through WWW have a structure where links form a 
loop (in such a manner that a link is traced from a certain document S and 
reference is made again to document S). At step S604, a loop-structure 
link is sensed. In the process of specifying a related document of a 
certain document, the documents already judged by the condition judging 
section are prevented from being judged again. 
The calculation of the degree of similarity using words in the document at 
step S609 is not restricted to the content by percentage of the common 
words in the specific part of speech (or the group of specific parts of 
speech), but may be made in other methods. For instance, synonyms may be 
regarded as an element for calculating the degree of similarity. In this 
case, when word W or its synonym W' included in document A at step S609 
coincides with word X or its synonym X', the word is also regarded as a 
common word. With this consideration, the percentage of words common to 
both documents is calculated. It is assumed that synonyms are defined in a 
collection of synonyms determined independently. 
Furthermore, a high-order word and low-order word of a word may be regarded 
as an element for calculating the degree of similarity. In this case, when 
at step S609, word W or its high-order word or low-order word W' included 
in document A coincides with word X or its high-order word or low-order 
word X', the word is also regarded as a common word. With this 
consideration, the percentage of words common to both documents is 
calculated. It is assumed that the high-order words and low-order words 
are defined in a thesaurus determined independently. 
Furthermore, the degree of similarity may be calculated using any 
combination of all of these words, synonyms, and high-order words and 
low-order words. 
The degree of similarity may be calculated in a different method from the 
method of finding the degree of similarity on a word basis explained in 
the embodiment. For instance, by analyzing the construction of sentences 
and meanings and extracting the meaning of a document, the degree of 
similarity between the documents can be calculated. 
Moreover, any combination of all of the condition judging methods described 
above may be used as another judging method. 
FIG. 12 shows an example of a collection of synonyms. In the collection of 
synonyms shown in FIG. 12, each of numerals 701, 702, and 703 defines 
words regarded as common words in a manner that sets them apart by "=". 
For example, by numeral 701, the word "computer", the word "computing 
machine", and the word "electronic computer" are all defined as common 
words. 
FIG. 13 shows an example of a thesaurus. A thesaurus has words arranged 
hierarchically in a conceptual manner. In FIG. 13, regarding the word 
"machine", words with lower-order concepts in meaning are defined 
hierarchically. 
As described so far, with the embodiment, the degree of association between 
each document specified by the URL included in the transferred document 
and the document specified by the first document request is determined on 
the basis of the depth of the link between the document specified by the 
first document request and each document specified by the URL or the 
degree of similarity between the contents of documents. The thus obtained 
degree of association is used to specify a document file to be received in 
advance. Therefore, even when a document having a lot of URLs is requested 
first or when each of the documents requested as related documents further 
has a URL specifying another document, the document requesting system can 
specify documents closely related to the first requested document. This 
enables only the function of the document requesting system acting as a 
WWW client to receive a suitable related document in advance without the 
function of the WWW server. 
As described in detail until now, with the present invention, the client 
side can specify a document to be received in advance as a related 
document, which makes it possible to receive a suitable document in 
advance with only the function of the client. 
Additional advantages and modifications will readily occur to those skilled 
in the art. Therefore, the present invention in its broader aspects is not 
limited to the specific details, representative devices, and illustrated 
examples shown and described herein. Accordingly, various modifications 
may be made without departing from the spirit or scope of the general 
inventive concept as defined by the appended claims and their equivalents.