Efficient online information service for materials science engineers and chemists providing full data from reliable sources decreases baseless papers' duplication and ultimately it reduces cost and time required creating modern materials. Inaccessibility and frequently dispersion of information over different heterogeneous data sources makes great difficulties in decision-making process considering application of one or another material.
During development of presented in this paper integrated information system key task was creation of intelligent, simple in architecture and effective software infrastructure. This software infrastructure should integrate data on substances and materials rationally and reasonably.
Integration means are required that should be capable to provide not only unified access to operating data centers, but these integration means should allow us to create comprehensive data access infrastructure that is based on unified standards and uniform network interconnection principles also. The first one implies full merging of existing resources. That is the case when database complex is a single information system megabase for end users, operators and administrators. Database exploitation costs reduction and information duplication decrease can be mentioned among advantages of such variant.
Every data center is a point of information concentration and online data analytical processing. In addition, technology of information accumulating and data processing is settled down in each organization. Moreover, great investments that were made in hardware and software do not allow solving the data dissociation problem by all data mechanical transportation to some centralized database. Moreover Russian databases on electronics materials were developed in various organizations and thus they took advantage of different database management systems DBMS.
Taking into consideration differences in data quality, data expertise, data store types and many other troubles emerging when changing existing systems operating principles it should be stated that full and smooth integration is practically impossible for above mentioned resources. The second integration approach main essence is that we are not going to integrate databases themselves, but we want to integrate their proprietary user interfaces only. From one hand this approach allows us not to change every integrated database structure dramatically and thus established database utilization and administration technology — data update and insert.
From the other hand, this approach allows to the end user to get access to the whole information picture on chemical substances that are stored in different databases.
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And that fact solves the main integration goal truly. Taking into consideration current development conditions of Russian databases on physicochemical substances' properties the second integration approach — integration at interface level only — is more appropriate and quite perspective. Database integration database on semiconductor systems phase diagrams. These Web- at Web interface level interfaces allow users to get remote access via Internet to data stored in these databases using any Web browser.
This information should be relevant to the data on some chemical system currently browsing by user. Thus, we hardly need to have some active data center that should know what information is contained in every integrated database. So some data store should exist that describes information contained in integrated database resources.
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In this manner, we come to the metabase concept — a special database that contains some reference information on integrated databases' contents fig. In our case, it is information on chemical systems and their properties. The amount of this metainformation should be enough to perform search for relevant information on systems and corresponding properties. Hence, metabase should contain information on integrated databases D set , information on chemical substances and systems S set and information on their properties P set.
So all we need to solve the task of searching for relevant information in integrated databases is to determine somehow the R relation. It is significant to note that R relation can be created or complemented by means of either of two variants.
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The first variant is via using predefined rules by a computer. Metabase concept The second one is that experts in chemistry and materials science can be engaged to solve this task. The second variant is quite clear — experts can form relationship R following some multicriterion rules affected by their expert assessments. One of such variants can be like this one based on the following rules: 1. R relation is symmetric.
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These two rules allow us to determine a set of chemical systems that are relevant to the given one. It should be noticed that this automatic R relation generation variant is just one of the simplest and most obvious variants of such rules, and in fact more complex mechanisms can be used to get R relation.
For example, browsing information on a particular property of a compound in one of integrated databases in fact, it is information defined by d1 , s1 , p1 triplet , we consider d 2 , s2 , p2 triplet to be relevant information. Metabase should store reference data on integrated resources contents.
Nowadays these technologies are capable of providing reliable infrastructure for cross platform message exchange. In that way reference information loading into metabase was implemented by means of metabase update Web service, so-called MUService fig.
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System that is to be integrated with others should Fig. Metabase update Web service generate XML document that contains information on updates in that very system. The layout format of this XML document is generally standardized for all integrated subsystems and it is strictly fixed by means of specially developed XML schema . Thus, all subsystems being integrated should generate valid XML document that meets XML schema requirements to notify metabase of information changes that occurred in their state.
After being generated, XML document is sent to the metabase update Web service for processing and metabase update. In that way client databases report about updates to the metabase and so actual information on integrated resources contents appears in the metabase. It guarantees secure metadata exchange with metabase update Wes service. Additionally an option for data archiving was included into the system.
A king of zip-achieving was implemented that allows us to package data that are transmitted to the metabase server. This feature allows dramatically decreasing data volumes taking into consideration high level of compression for XML documents that are transmitted via public networks. Thus this feature lowers requirements to network bandwidth and it is very important and actual for Russia since high-speed Internet access is not available everywhere in the country.
Compressing techniques enable us to decrease information volumes so that it becomes possible to use old-fashioned data modems on telephone wires to transmit data. As it can be seen, metabase update Web service supports some rather complex additional data transformations encryption and archiving that require some extra coding. So to simplify the interaction process with the Web service special Web client was created. Created Web client addresses issues connected with encryption and compression of information that is to be sent to the Web service. It controls all network interconnection aspects also.
All this functionality just simplifies routine database attachment to the integrated system. It should be mentioned that at present time only integrated database systems as client systems to the metabase could initiate data update process with metabase update Web service. This technique of course is not the only variant of interaction scheme. Thus it is planned to redesign metabase update mechanism so to enable metabase to inquire integrated resources on demand and thus to query information updates occurred.
It should be mentioned that after every metabase update session incremental population crawl is started on the metabase to update or to reindex relevant chemical systems list regarding information changes. TECH 31 metabase to maintain actual information on relevancy relation of chemical systems contained in integrated resources. Currently relevant system reindexing is performed by means of approach of two rules proposed in this paper earlier.
If it is necessary, these rules can be easily modified. And the main advantage is that in that very case it is not necessary to redesign the whole system concept. All we have to do is just write a new piece of software to provide a new method of searching for relevant systems and replace the old module with the new one. In a general sense, the integration of information resources of materials' science is in consolidation of available Web applications serving users of different materials' science databases.
This consolidation is provided by means of specialized software but user should not be aware of it if possible. The software should be transparent in this sense. When designing the integrated system special attention was paid to security system development. It should be mentioned that every developed information system has its own proprietary security facilities that protect the system and give permissions to access it. Security system of a particular information system is responsible for granting permissions to registered users of given system only.
Metabase integration — how it works. From our point of view, the described approach is an appropriate one and so it is used to design the distributed security system of integrated databases. It should be mentioned that user credentials of every integrated resource are also transmitted to the metabase via MUService as well.
It is done to organize distributed security system operation in cooperation with corresponding security systems of integrated resources. It should be emphasized that open user passwords are not transmitted to the metabase, instead of open passwords, password MD5 hashes are transmitted in fact. This substitution MD5 hash instead of open password allows integrated information system to authenticate active user and at the same time this technique excludes possibility of using open user password to login to the integrated system database.
In other words, there is no place for vulnerabilities here. So even if this data are stolen integrated resources can not be compromised. In other words, the user is in Web application of a particular information system fig. If it is necessary to get relevant information this Web application is capable to send a request to specially developed Web service  that serves users of integrated system. The request aim is to get information contained in integrated resources that is relevant to the currently browsed data. As it was mentioned, earlier data in XML format are properly understood on all major platforms.
The user can follow from one Web application to another to browse relevant information via this gateway only. Imagine that the user clicks on a hyperlink to start browsing information from some other integrated system. First of all, when the user has clicked the hyperlink, he is forwarded to the special gateway. Actually it is a specialized Web application that runs on the metabase Web server. The gateway main purpose is to perform security-dispatching function in distributed system.
According to the task stated it is responsible for user authentication and it also checks whether the user has required privileges to address the information requested. It should be stated that the entry point is a specialized page in target Web application that is to perform service functions for integrated system users. At this very page target Web application checks digital signature of the metabase security gateway and if everything is ok the page creates special security context for user with given access rights within target Web application.
Finally, the user is automatically redirected to the page with the information required.