Figure 1. Relationships among data IDs obtained from 13 databases. Here, INSD is represented by NCBI. For all these IDs, the HMS and the ID Converter System are capable of setting hyperlinks and ID conversion. ‘Common IDs’ that were used as key IDs in ID conversion are shown in red, blue or green. Lines connecting databases represent the paths of ID conversion. For example, when converting HUGO Gene Symbols into PDB IDs, the system ﬁrst converts HUGO Gene Symbols into accession numbers according to a corresponding table obtained from NCBI, and then converts accession numbers into UniProt IDs according to a corresponding table obtained from UniProt, and then converts UniProt IDs into PDB IDs according to a corresponding table obtained from PDBj. Live lists of data IDs and their corresponding tables are collected daily from each of these databases. are more than one IDs corresponding to the source ID, the HMS shows the list of all corresponding data IDs with appropriate hyperlinks, from which users can choose and open the data of interest. In order to create hyperlinks using the HMS CGI- program, use the following URL as a target URL. http://biodb.jp/hfs.cgi?id=[ID]&type=[ID Type]&db= [Database Name] Here, [ID] is a data ID of the database from which hyperlink is set, [ID Type] is a kind of the data ID and [Database Name] is the name of database to which hyper- link is set. Details of parameter settings are shown in Tables 1 and 2 and also in the online HELP pages of the HMS. For example, using BC053 657, an accession number of INSD, you can create a hyperlink toward the corresponding ‘Transcript View’ of H-InvDB in the following way. <a href = "http://biodb.jp/hfs.cgi?id=BC053657&type= ACC_ID&db=TRANSCRIPTVIEW">BC053 657</a> This CGI-program is freely available to all users in the world. For database managers, if their databases have any one of those data IDs shown in Table 2, it is possible to create hyperlinks from the database to all the databases shown in Table 1 through the HMS. Because the hyperlinks of the HMS are automatically updated Nucleic Acids Research, 2009, Vol. 37, Web Server issue W19 everyday, the connection to the latest data is always guaranteed. Usage of the HMS Web Server The HMS CGI-program is supposed to be used for hyper- linking among databases. However, there are situations that we want to query with a small number of data IDs. We thus developed a Web server of the same function as the CGI-program (Figure 2). Here, by utilizing the same corresponding tables of data IDs as those of the CGI version, users can open Web pages of a database corre- sponding to a speciﬁed data ID of another database. The usage of the HMS Web server is quite simple and requires no complicated explanations. For example, if you enter an accession number of INSD in the ‘Source ID’ and push the ‘Search’ button, you can open the ‘Locus view’ of H-InvDB. In the textbox, users can enter multiple data IDs delimited by a space, tab or comma. In this case, the result page shows a list of multiple URLs with hyper- links corresponding to each data. Usage of the ID Converter System (ICS) ICS is a tool for converting data IDs used in a database into other, corresponding IDs used in other databases (Figure 3). All the data IDs used in the HMS can be dealt with. Multiple IDs can be converted at a time, if users enter multiple data IDs delimited by a space, tab or comma. When a data ID can be converted into multiple corresponding IDs, the ICS shows all the corresponding IDs. Users can also specify a ﬁle on their client PC, and convert a list of data IDs in it. Furthermore, the ICS is accessible by computer programs using the Web service, as will be described later. Web service and other functions For those who wish to analyze massive data by computers, the HMS and ICS accept queries through the Web service, which makes it possible to call functions of these systems through computer programs. The details of commands for the Web service will be shown if you click the ‘Web service’ button on the upper right corner of the Web pages (Figures 2 and 3). On these pages, there are some sample programs for the Web service. Furthermore, we prepared statistics pages of the HSM and ICS. If you click the ‘Update Info’ button on the upper right corner of the top pages (Figures 2 and 3), the number of data IDs downloaded from each database everyday will be shown. If you click the ‘Release Info’ button, the number of pages of each database that are hyperlinked through various data IDs will be shown. Finally, there are help pages that explain how to use the HMS and ICS. DISCUSSION As has been stated earlier, there are currently 1170 data- bases in the ﬁeld of life sciences that are listed in the online Molecular Biology Database Collection of Nucleic Acids