Medical Informatics. Учебное пособие

The following types of resources correspond to three main components on the Internet: hardware, software and information. Do not forget that all these types of resources are someone’s property. It may be private property, corporate property, state property and public property.

The hardware resources of the Internet are represented by the so-called Internet backbones, which are connected to the service providers. Connecting to the Internet, we actually use hardware resources of the computer that provides that connection. It allocates a portion of its processor power, ram memory and in many cases a portion of its space on a hard drive or other storage devices according to our objectives. In addition, we exploit the physical resources of communication lines, involving our signals. Their transmission capacity may be very large, especially for fiber-optic and space lines, but it is not un limited. Rebooting slows down data transmission, interference between signals starts, which leads to the failure and retransmission. In short, every person using the hardware resources of the Web, in one way or another complicates the work of other members of the Network. On the powerful sections of the network equipped with high-performance computer systems and powerful communication trunk lines, it is imperceptible at sites equipped with poor technique and primitive communication channels, the impact of some users on the comfort of other users is very large.

Software resources of the network are presented with programs that operate as part of the network equipment. Our work in the web is served by thousands of programs running on the computers through which our requests pass to providers of information. All these programs belong to someone on the right of ownership (by producers) and on the right to use (those who have them installed).

In most cases, network users do not have any rights to the software that serves them. Interference in its work is considered illegal and is punishable under the laws of the country in which the offense against the law occurred. That should be kept in mind when using the Internet and avoid even unintentional interference in the work of programs, located on remote computers, except for those very rare cases when it is provided by the very nature of the work of the program.

41

Network information resources are available in the documents stored on networked computers. Depending on the ownership these resources can be open or closed (public or private). In the latter case, to gain an access you need to lay claim. This is usually done by declaring his/her user name (login) and password. Access right save either purchased (paid for), for example by addressing to the commercial resources, or provided by the administration, for instance for employees of the enterprise, institution or agency. Violation of cyber law through unauthorized access to the software operation, which, as we noted above, constitutes a crime under the laws of most states. In Russia, in this regard, there are articles 159, 272, 273, 274 of the Russian Federation criminal code.

Most of information resources of the Internet are open resources: texts, images, sound and video recordings, etc. Despite of their openness, they should not be regarded as public ownership. In most cases people view these resources as shareware, that is, they are treated as open for personal consumption (reading, watching, listening etc.), but in all other cases (reproduction, publication, modification, demonstration etc.) they are subject to the laws of the country where users are permanent residents. In Russia, this issue is stipulated in paragraph 111 of the copyright law.

The Internet has two main functions: information and communication.

The information function allows users to obtain the requested information quickly. It can be scientific knowledge, technical documents, books, manuals, articles, reports, drawings, diagrams, pictures, videos, sound recordings and so on.

The communication function of the Internet allows to exchange rapidly social, professional and other types of information. At present, the computer has gradually turned from a highly specialized computing device into a universal communication tool.

13.3 Internet protocols: TCP / IP, PPP, POP3, SMTP. Their function and

user’s view (interface, presentation)

42

Simple connection of one computer to another is a necessary step to create a network, but not sufficient. Before you transfer information, make sure that the computers "understand" each other. How do computers “communicate” on the network? In order to provide this capability, special tools, called "protocols", have been developed. A protocol is a set of rules which work together to transmit information across computer networks. The concept of “protocol” is applicable not only to computer industry. Even those people who have never had anything to do with the Internet, most likely worked in everyday life with any devices whose operation is based on the use of protocols. For example, the public telephone network also has its own protocol that allows devices to determine the fact of lifting handset at the other end of the line, or to identify the disconnect signal and even the number of the caller.

Based on this natural necessity, the world of computers required a universal language that would be clear to each user.

Network protocol is a system of rules and actions (prioritization of actions) which allows for the connection and exchange of data between two or more network enabled devices.

Different protocols often describe only the different sides of one type of communication. Taken together, they form a protocol stack. The names of "protocol" and "protocol stack" also point to the software that implements the protocol.

The most common classification system of network protocols is the so-called OSI model (the Open Systems Interconnection model). It divides network architecture into seven layers for its intended purpose - from the physical layer (formation and detection of electrical or other signals) to the application layer (application programming interface to transfer information by applications).

The main suite of protocols used on the Internet are:

TCP/IP

POP3

SMTP

FTP

43

HTTP

IMAP4

TCP / IP. The best human minds worked on the creation of protocols, required

for the existence of the global network. One of them was Vinton G. Cerf. Now this man is recognized as one of "the fathers of the Internet." In 1997, US President Bill Clinton awarded Vinton Cerf and his partner Robert E. Kahnwith National Medal of Technology for creating and sustaining development of Internet Protocols”. Now Vinton Cerf is a senior vice president of Internet architecture Board at MCI Corporation World Com Inc.

In 1972 a group of developers under the direction of Vinton Cerf designed and developed TCP / IP (Transmission Control Protocol / Internet Protocol).

The experiment was carried out for the USA Ministry of Defense. This project was named ARPANet (Advanced Research Projects Agency Network - Network Agency of important research projects). Obviously, in wartime, when the need to share information arises more than ever, there is a problem of unpredictability of the state of information transfer path Any of transmission nodes can be brought out of operation by the enemy at any time. Therefore, the main objective in the design of network protocols is its (unpretentiousness, simplicity) "ruggedness". It would work with any network environment and, moreover, have flexibility in selecting a route for information delivery.

Later, TCP / IP has outgrown its original purpose, and became the basis of the rapidly evolving global network now known as the Internet, as well as smaller networks using Internet technologies - intranet. TCP/IP standards are open and continuously improving.

Actually, TCP/IP protocol is not a single but a whole set of protocols that work together. It is a two-layer program. The higher layer, TCP (Transmission Control Protocol), manages the assembling of a message or a file into smaller packets that are transmitted over the Internet and received by a TCP layer that reassembles the packets into the original message. The lower layer, IP (Internet Protocol), handles the

44

address part of each packet so that it gets to the right destination. . Sometimes packets of the same message can be delivered in different ways.

HTTP. (Hypertext Transfer Protocol) is a higher-level protocol with respect to protocol TCP/IP - Protocol Application Layer. HTTP was designed for efficient transmission of Web-pages over the Internet. Thanks to HTTP we are able to contemplate the Network pages in all their glory. The HTTP protocol is the basis of World Wide Web.

You give commands to HTTP, using the browser interface, which is the HTTPclient. When you click on the link the browser asks the Web-server for the data of the resource being referenced - for example, another Web-pages.

The addresses of Internet resources that you access over HTTP, looks like this: http://www.tut.by.

FTP. (File Transfer Protocol) is specially designed to transfer files over the Internet. Later, we'll talk about it in details. Now let's say only that the address of FTP-resource on the Internet looks as follows: ftp://ftp.netscape.com.

POP3. Post Office Protocol (Version 3) is used for the delivery of email from a mail server. ROR3 design allows the user to contact your mail server and remove the accumulated mail. The user can access the POP server from any Internet access point to the Internet. However, the user have to run a special mail user agent (UA), operating protocol ROP3and configure it to work with your mail server.

IMAP4. (Internet Message Access Protocol) allows e-mail clients to access and manipulate e-mail messages on the server. The essential difference of IMAP4protocol from ROP3 is that IMAP4 supports system directories (or folders) of deleted messages in the same way as if they were located on a local computer. IMAP4 allows the client to create, delete and rename mailboxes, check for the new messages and delete the old ones. Due to the fact that the IMAP4 supports the mechanism of unique identification of each message in the mail folder of the client, it allows you to read from the mailbox only those messages that satisfy certain conditions or part of them and to change the attributes of messages and relocate individual messages.

45

SMTP (Simple Mail Transfer Protocol). Mail transfer agent (MTA) is the main component of the mail transfer system on the Internet. SMTP requires to get answers from SMTP commands receiver. The exchange of commands and responses to them is called mail transaction. The data are transmitted in the NVT ASCII format. In addition, the commands are also transmitted in the NVT ASCII format. Commands are sent in the form of key words, rather than the special characters, and show the need for performing one or other operation.

Powerful server computers that are constantly turned on and connected to each other form the basis of the Internet. It is these computers that process and direct information flow through worldwide network. At present millions of servers work on the Internet.

13.4 Operating systems of personal computers

Currently, computer technology has become a reliable assistant for a physician, greatly enhancing his intelligence, diagnostic capabilities, freeing him from routine work, giving unprecedented opportunities to generalize medical data and conducting medical and statistical experiments.

To work effectively, every computer user must have a good understanding of fundamentals of computer systems organization.

Any computer system (CS) has at least three types of support:

•methodological support;

•hardware;

•software

The methodological support includes setting targets to address them using computer technology. Methodological support provides knowledge of how to deal with certain medical problems, which input information and in what form should be collected, what kind of output information must be obtained, how to get output information from the input one. The whole process of training at the academy, from the point of view of studying medical computer systems, can be represented as the acquisition of knowledge in the area of methodological support.

46

• manages the file system.

Utilities are OS supporting software that provide users with the most frequently used means of data processing.

Operating systems are classified as follows (see Fig. 5).

Operating systems

Fig. 5 Classification of operating systems

A typical single-user single-tasking system is the operating system MS-DOS. Operating systems UNIX, XENIX, DEMOS, INMOS and MOS are multiusers and multitasking.

13.6 The basics of evidence-based medicine

The comparison of the body state under normal and pathological condition, before and after the treatment, or the use of different methods of treatment occupy a highly important place in medical research.

Generalizing numerical characteristics obtained during the sampling of medical and statistical studies are used to analyze and give objective assessment of the results of various types and activities of medical service units and institutions.

In medicine, it is practically impossible to name a single study in which it would be possible to do without solving the problem of statistical evaluation of the significance of differences of the obtained general indicators (assessment of dynamics of indices of physical development of different age groups; comparison of the effectiveness of treatment of several groups of patients; assessment of changes in the activity of one or the other systems and organs of human or experimental animals

48

under various extremes and other factors; assessment of the major and side effects of drugs, etc.). Any clinical, experimental and laboratory medical research that needs to reply to a question about the effectiveness of the applied method of treatment, cannot be considered scientifically valid without statistical reliability assessment of changes in relevant medical parameters. Just strictly follows a similar approach to solving the issues of medical science, in all cases the assessment of efficiency and quality of measures aimed at preserving and improving the health of all population groups.

Comparison of indices is performed after considering the results of sample survey (sampling).Reliable results can only be obtained on representative samples of sufficient volume.

14. Medicine, based on evidence-based approach. Provision of evidence-

based approach in medical research

Evidence-based approach is a social act. What presume to be proved and what not depends on the adoption and unambiguous interpretation by all parties concerned of propositions that do not require evidence and the rules of evidence procedure.

The cornerstone of statistical proof is the concept of statistical hypothesis. Hypothesis is a proposal that needs evidence. By convention all hypotheses can be divided into testable (verifiable) and unchecked (unverifiable) hypothesis. Naturally, we are interested only in verifiable hypothesis. Hypotheses testing may be carried via direct evidence-logically or by experiment. If there is no direct evidence ,the procedure of hypothesis testing via indirect evidence is used.

The indirect testing involves the analysis of some consequences that logically follow the content of the hypothesis. As the result of this analysis, it is desirable to have the opportunity to recognize the hypothesis true or false.

The hypothesis may be considered false:

a)if a phenomenon that logically follows the hypothesis is not observed in nature;

b)if there is something that in case of hypothesis validity should not happen. With regard to the situation when the hypothesis can be assumed true, it should be

stated that the experimental results, consistent with testable hypothesis, hardly ever prove

49

its validity. In other words, confirmation of consequence does not mean the validity of the hypothesis, because the correct conclusion may result from an incorrect premise.

It follows that the hypothesis can not be proved indirectly, but it can be rejected (refuted). It should be noted that in daily practice, the accumulation of a great number of indirect evidence, as a rule, is regarded as sufficiently convincing proof of the validity of the hypothesis.

If the hypothesis is verified on the basis of sample data, so the statistical testing of hypothesis is under way. The procedure of statistical testing lies in determining the probability of how compatible is the hypothesis with the observed random result. In light of the above stated proposition, the statistical hypothesis is a hypothesis, verifiable by

statistical testing.

We can say, that the art of statistics application involves the ability to nominate competently and test correctly the statistical hypotheses.

The construction of the proposed statistical hypothesis, following the logic of what has been said with respect to indirect evidence, should be opposite to the fact or statement which is necessary to prove.

The hypothesis formulated by the specified principle is called the null hypothesis and is denoted as H0; the opposite hypothesis is called alternative and is denoted by H1.

Thus, when comparing the figures, for example, in the control (healthy) and experimental (pathology) groups the following statistical hypotheses are put forward:

-H1 – about a significant difference in the index in experimental and control groups;

-H0 – about the equality (compliance) of the index in experimental and control groups. When checking (testing) the statistical hypothesis the paradox of infinity of proof

(evidence) potentially takes place: if in consequence of n experiments the tests validity of the null hypothesis is not refuted, it does not mean that it has been proved because the of ( (n 1) experiment can refute it. To avoid the situation with infinity of the procedure and evidence probabilities of possible errors are regulated. Errors which are principally possible in the hypothesis testing are divided into two main classes:

- a type I error (error of the first kind) is the incorrect rejection of a true null hypothesis;

50