Conventional software management

1. The crucial analysis made regarding the state of the software engineering industry was carried out in mid90's.

2. Though the analysis was done from a different point of views, the actual message resulted from the analysis were complementary and consistent.

3. The degree of predicting software development is very low due to which more than 90% of a software project is delivered unsuccessfully.

4. There may be several reasons for the failure of software project such as project may consume more money and time than expected, the project may fail to meet the customer requirements.

5. Management discipline is not considered as a technology advances but it is treated as a software management factor, which is a primary discriminator for specifying the success and failure of the project.

6. The process is said to be immature if the level of software scrap and the amount of rework performed is very high.

7. All three analyses resulted in the same general conclusion which states that the level of the success rate associated with the software project is very low.

8. Jones in 1996 made a presentation regarding the state of the software industry by analyzing the results of many projects, which were grouped into the following six sub-industries.
     1.System software.

     2.Information systems.

     3.Commercial software.

     4. Outsource software.

     5.Military software.

     6.End-user software.

9.When there is no information regarding the historical software measurement data.

10.When the project fails to use automated estimating tools, automated planning tools, effective architecture, effective development methods, design reviews, code inspection.

11.When the project fails to examine the progress.

12.When the project employs informal testing methods.

13.When design, as well as specification, are done manually.

14. The computer program must be developed twice and the second version which takes into account all the critical design operations must be finally delivered to the customer for operational deployment.

15. The first version of the computer program involves a special broad competence team, responsible for notifying the troubles, in design, followed by their modeling and finally generating an error-free program.

16. The test phase is the biggest user of the project resources, such as manpower, computer time and management assessments.

17. It has the greatest risk in terms of cost and schedule and develops at the most recent point in the schedule when backup alternatives are least available.

18. Thus, most of the problems need to be solved before the phase, as it has to perform some other important operations.

19. Hire a team of test specialists who are not involved in the original design.

20. Apply visual inspections to discover the obvious errors, such as skipping to wrong addresses, dropping of minus signs, etc.

21. The customer must be involved in a formal way so that he has devoted himself to the initial stages before final delivery.

22. The customer's perception, assessment, and commitment can strengthen the development effort.

23. Hence, an initial design step followed by a preliminary software review, critical software design reviews, during design and a final software acceptance review, after testing is performed.

Model-based software architectures

1. The objective of model-based software engineering is to improve product cycle time, product quality and product maintainability through a formal understanding of the features and structure of a product family and through the development of reusable software resources that simplify the development of the new product in the family.

2. In MBSE, these reusable resources are designed for flexibility.

3. They will not easily fail as changes occur in functionality, performance.

4. Much of the technology in MBSE is not new, but by focusing on models that consolidate engineer's understanding of a family of software products, engineers can create reusable assets that satisfy a wide variety of uses and easily analyze changes in existing software to quickly compose new solutions for subsequent products.

5. The design of a software system is an architecture.

6. The goal of an engineering stage is to converge on a stable architecture baseline.

7. This architecture baseline is not a paper document and it is a collection of information across all the engineering sets.

8. These architectures are described by extracting the essential information from the design models.

9. In today's software systems, we have to evolve the multiple distinct models and views to exploit the advantages of modern technologies such as commercial components, object-oriented methods, open systems, distributed systems, host and target environment, and modern languages.

10. A model is defined as an abstraction of a system that is independent in nature.

11. The view is defined as a subset of the model, which outlines a definite, related perspective.

12. Hence, multiple models and views have evolved to make good use of modern technologies like object-oriented methods, distributed systems, open systems, etc.

13. Architecture is considered as the most important technical product of a software project.

14. The infrastructure, control and data interfaces allow for software components to collaborate as a system and for software designers to have mutual support as a team.

15. If the software development team needs to have the path of success, then the inter-project communications must be precise and accurate as in software architecture.

16. The three different aspects of software architecture from a management perspective are as follows.

17.It is an indefinite design of software system.

18. It includes the following, All engineering requirements to specify entire material bills.

19. Important make/buy decisions are solved.

20. All custom components are clearly explained so that the cost of each component and construction/assembly costs can be determined.

21. It is a definite aspect of software architecture.

22. It is a subset of information across engineering artifact sets so as to satisfy all stakeholders that function and quality can be achieved within the business case parameters like cost, time, profit, etc. 

The structure of physical disk

1. Data on the disk is recorded on tracks, which are concentric rings on the platter around the spindle.

2. The tracks are numbered, starting from zero, from the outer edge of the platter.

3. The number of the tracks per inch on the platter measures how tightly the tracks are packed on a platter.

4. Data on the physical disk can be divided into tracks, then it can be explained as follows.

5. Each track is divided into smaller units called sectors.

6. A sector is the smallest, individually addressable unit of storage.

7. The track and sector structure is written on the platter by the drive manufacturer using a formatting operation.

8. The number of sectors per track varies according to the specific drive.

9. The first personal computer disks had 17 sectors per track.

10. Recent disks have a much larger number of sectors on a single track.

11. There can be thousands of tracks on a platter, depending on the physical dimensions and recording density of the platter.

12. Typically, a sector holds 512 bytes of user data, although some disks can be formatted with larger sector sizes.

13. In addition to user data, a sector also stores other information, such as sector number, head number or platter number, and track number.

14. This information helps the controller to locate the data on the drive, bu storing this information consumes space on the disk.

15. There is a difference between the capacity of an unformatted disk and a formatted one.

16. Drive manufacturers generally advertise as being 500GB will only hold 465.7GB of user data, and the remaining 34.3GB is used for metadata.

17. A cylinder is the set of identical tracks on both surfaces of each drive platter.

18. The location of drive heads is referred to by cylinder number, not by track number.

Access Time Characteristics:

1. The access time or response time of a rotating drive is a measure of the time it takes before the drive can actually transfer data.

2. The factors that control this time on a rotating drive are mostly related to the mechanical nature of the rotating disks and moving heads.

3. It is composed of a few independently measurable elements that are added together to get a single value when evaluating the performance of a storage device.

4. The access time can vary significantly, so it is typically provided by manufacturers or measured in benchmarks as an average.

5.SSD's this time is not dependent on moving parts, but rather electrical connections to solid-state memory, so the access time is very quick and consistent.

Goals of data management

1.Supply work, business and consumption processes with information.

2. Improve and speed up business work and consumption processes through information use and efficient information processing.

3. Information is not only one of the inputs to the work process.

4. By improving information supply and its processing, the whole process usually can be made more efficient.

5. Create and maintain competitive advantages through new, IT-based work and business processes: Often, information technologies allow the reorganization of work in completely new ways and the creation of totally new businesses.

6.Efficient use of an organization's information assets.

7. Reduce unnecessary complexity of information processing systems, protect against information overload.

Accessibility problem:

1. Broadly, there are sub-dimensions to the problem.

2. One is distributed information the information is stored in different computers and managed by different information management systems or by different applications.

3. This, in turn, has two cases, depending on whether the existence, location and access requirements of some elements of the distributed information are known or not know.

4. Another dimension of the accessibility problem is the semi-structured data and multimedia data.

5. While such data as records in a relational database table, and records in files are regarded as structured data, such data as emails, XML documents, and all types of forms are regarded as semi-structured data.

6. Multimedia data includes photographs, satellite images, video clips, audio clips, television broadcasts, etc.

7.If semi-structured data or multimedia data are not impossible for computers to search for them or match them with given sample data.

8. There are commercial products for automatically matching images, such as fingerprints and faces, matching audio, including voice, music, and sound, recognizing anomalies in images and audio, creating indexes for fast search and matching of images, audio, and video, etc.

9. This refers to the retrieval and presentation of too much information that is not relevant to the needs or intentions of the people seeking such information, even when the information access problem has been addressed.

Periodic status assessments

1. The interacting activities of software development require continuous attention in order to manage risks and to assess the project status.

2. Periodic status assessments are defined as the management reviews carried out at regular intervals so as to indicate the progress and quality indicators, paying continuous attention to project dynamics and maintaining communication among all stakeholders.

3. Periodic status assessments are the periodic events in which, management reviews the progress of a project in a regular manner, so as to achieve stakeholder's expectations.

4. Periodic status assessments are considered as one of the critical project checkpoints as it provides special consideration to the gradual development of the project priorities.

Functions of status assessments:

1. The status assessment aims at the periodic occurrence of stakeholder's expectations.

2. Status assessments are carried out by the management in order to check the development of a project in a periodical manner.

3.Deals with issues related to the progress of project status or assessment of status.

The need for status assessments in the software life cycle:

1. The main goal is to fulfill the stakeholder expectations in s synchronized and consistent manner.

2. Status assessments serve as periodic snapshots of a healthy project which includes assessment of risks, management indicators, and quality indicators.

3. Status assessment documents provide the mechanism for satisfying everyone's expectations, for communicating and solving the management, technical issues, and project risks.

4. They provide objective data from on-going activities for developing product configurations.

5. It also provides a mechanism for the widespread use of a process, progress, quality trends, practices and experience information to all the stakeholders in a to and fro manner.

6. Status assessments force the project manager to conduct periodic review and to collect the necessary data in order to have good health of the project.

7. Typical status assessments include resources review, personnel staffing, financial data i.e., cost and revenue, top 10 risks, plans related to major milestones, the scope of product, consequences and technical progress like metric snapshots, etc.

Transmission characteristics of twisted pair cables

1. For transmitting analog signal, amplifiers are needed at every 5 to 6 km intervals so that signal is not weakened and for transmitting analog signal digital signal using digital transmission, repeaters are needed at every 2 or 3 km intervals.

2. The data rate of twisted pair for short distance is 1 Gbps which are limited to a confined area and for long-distance, it is 4 Mbps or more.

3. Twisted pairs are restricted with respect to distance, the capacity of the channel, rate of data.

Types of twisted pairs cables:
They are two types of twisted-pair cables.

1). Unshielded twisted pair cable

2). Shield twisted pair cable

(1).Unshielded twisted pair cable: In UTP, there is no shielding around the twisted pair.

2.UTP is generally used in telephone companies and for computer networking.

3. The absence of shield results in greater flexibility and durability.

4.UTP is used in an Ethernet system and also in the token ring.

Advantages:

1.UTP is very easier to work.

2. The installation procedure is very.

Disadvantages:

1. Due to the lack of shield UTP is highly susceptible to electromagnetic interference.

(2).Shielded twisted pair cable: In STP, there is a tough protective shield over each pair of copper wire that is used to reduce the electromagnetic interference that occurs during transmission.

1. Stp is used in order to telephone networks and data communication that decreases the external disturbances.

Advantages:

1. Reduce external interferences.

Disadvantages:

1.Harder to work.

2.Expensive when compared to UTP.

Different categories of UTP:

1.Cat-1: The maximum data rate of cat-1 UTP is up to 1 Mbps.

2. It is generally suitable for low-speed data transmission.

3.Cat-2: The maximum data rate is 4 Mbps and used in token ring networks.

4.Cat-3: The maximum data rate is 16 Mbps and used in an ethernet system for transmitting both voice and data.

5.Cat-4: The maximum data rate is 20 Mbps.

6.Cat-5:Data rate category-5 UTP is 100 Mbps.

7. It consists of a 4-pair of wires.

Network protocol system hierarchies generalized network software system

1. In computer networks, communication occurs between entities in a different system.

2. An entity is anything capable of sending or receiving information.

3.Example include application programs, browsers, database management systems etc.

4. For communication to occur, the entities must agree on a protocol.

5. A protocol is a set of rules or agreements between the communicating parties, to indicate what is communicated, how it is communicated and when it is communicated.

6.Syntax: IT refers to the structure or format of the data, the order in which they are presented.

7. For example, a simple protocol may consider the first 8 bits of data to be source address, next 8 bits to be destination address and remaining its ate data.

8. Some other protocols may assume in a different order.

9.Semantics: It refers to the meaning of each section of bits.

10.Timing: It refers to two characteristics.
      (1).When data should be sent.

      (2).How fast it can be sent.

11. To reduce the design complexity, most networks are originated as a series of layers or levels, each one built upon the one below it.

12. The number of layers, the name of each layer, the content and the function of each layer differs from network to network.

13.The common purpose of each layer in almost all networks to offer certain services to the higher layers, shielding those layers from the details of how the offered services are actually implemented.

14. Layer n on one machine carries on a conversation with layer n on another machine.

15. The rules and conventions used in this conversation are collectively known as the layer n protocol.

16. The entities comprising the corresponding layers on the different machines are called peers.

17. In reality, no data directly transferred from layer n on one machine to layer n on another machine, instead each layer passes data and control information to the layer immediately below it, until the lowest layer is reached.

18. Between each pair of adjacent layers, there is an interface.

19. The interface defines which primitive operations and services the lower layer offers to the upper layer.

20. A set of layers and protocols is called network architecture.