Software Requirements Specification

Software Requirements Specification

for

Automated Railway Reservation System

Huitang Li

Vahid Keshmiri

Yasin Esmail

Zaida M. Morales

Natasha Dunaeva

Rehan Khan

October 24, 2000

Version	Changes Made	Date
1.0	First Pass for Review	10/24/2000

1. Introduction.

1.1 Purpose.

This document describes the software requirements for the Automated Reservation System built for the Chinese Railway Ministry. This specification is written after the recommendations of the IEEE standard 830-1993 [3] as approved by the IEEE Standards Board an December 2, 1993.

1.2 Scope.

The Chinese Railway Ministry (CRM) is requesting proposals to build a prototype of an Automated Railroad Reservation System (ARRS) for their current system. This new ARRS needs to be scalable enough so that it can accommodate the increase in reservations caused by new railroad building in China.

. The system will be designed to provide an electronic version of the railway passenger reservation system in China. The system will have a user-friendly graphical interface and will be more cost effective compared to the current non-electronic version of the reservation system.

The objectives of this development effort are:

· To provide existing clerks with a new environment in which to make reservations for railroad travel.

· To provide an avenue for customers to get their tickets in a more convenient way.

· To regain control of the railway ticket sales to avoid scalping and overselling of tickets.

· To implement a prototype of a scaled down version of the final system to test the solution and further develop requirements.

· To collect statistics in a more efficient manner for future railroad development and construction.

· To increase efficiency of railroads.

1.3 Definitions, Acronyms, and Abbreviations.

ARRS – Automated Railroad Reservation System

CITS – China International Travel Agency

CRM – Chinese Railroad Ministry

PP - Project Plan

SDD - Software Design Description

SRS - Software Requirement Specification

SDS – Software Design Specification

SPMP - Software Project Management Plan

GUI – Graphical User Interface

QAM – Quality Assurance Manager

PDM – Project Development Manager

TBD – To be determined

1.4 References.

· Introduction – Chinese Railway Passenger Reservation System Prototype

http://www.cs.swt.edu/~donshafer/project_documents/5391_Case.html

· China 2000

§ http://www.china2thou.com

§ Pressman, Roger S., Software Engineering: A Practitioner’s Approach, McGraw-Hill Companies, Inc., 1997.

1.5 Overview.

Chapter 2 of the SRS is a brief description of the characteristics of the software to be built, its functions and users, its constraints and its dependencies.

Chapter 3 is about specific requirements, such as functional requirements, external interface requirements, performance requirements, and also design constraints and quality characteristics.

Finally, chapter 4 includes all the supporting information, such as the Table of Contents, the Appendices, and the Index.

2. The General Description.

Describe the general factors that affect the product and its requirements. This section usually consists of the five

subsections that follow. This section does not state specific requirements; each of its subsections makes those

requirements easier to understand; they do not specify design or express specific requirements. Such detail is

provided in section 3.

2.1 Product Perspective.

This subsection of the SRS relates the product to other products or projects.

(1) If the product is independent and totally self-contained, it should be stated here.

(2) If the SRS defines a product that is a component of a larger system or project:

(a) Describe the functions of each component of the larger system or project, and identify interfaces

(b) Identify the principal external interfaces of this software product (not a detailed description)

A block diagram showing the major components of the larger system or project, interconnections, and external

interfaces can be very helpful.

2.2 Product Functions.

Provide a summary of the functions that the software will perform. Sometimes the function summary that is necessary

for this part can be taken directly from the section of the higher-level specification (if one exists) that allocates

particular functions to the software product. The functions should be organized in a way that makes the list of

functions understandable to the customer or to anyone else reading the document for the first time. Block diagrams

showing the different functions and their relationships can be helpful. Such a diagram is not a requirement on the

design of a product itself; it is simply an effective explanatory tool.

2.3 User Characteristics.

Describe those general characteristics of the eventual users of the product that will affect the specific requirements.

Many people interact with a system during the operation and maintenance phase of the software life cycle. Some of

these people are users, operators, and maintenance and systems personnel. Certain characteristics of these people,

such as educational level, experience, and technical expertise impose important constraints on the system's operating

environment.

2.4 General Constraints.

Constraints, under which the project is to be conducted, are:

· The number of trains from city A to city C and from city C to city A is limited to 5 trains.

· The number of passengers that can be taking a train at once is limited to 1080 passengers.

· The number of trains that can travel from city B to city A is limited to one and the number of trains that can travel from city A to city B is limited to two.

· The functional prototype should be available after 30 days upon the arrival of the management team to China. This may prove to be a serious time constraint on the development of a successful prototype.

· Communication with the Chinese team members may prove to be difficult since some Chinese developers do not speak English and the management team does not speak Chinese. Even with the presence of a translator, communication may be difficult. Absence of the translator may severely affect project development.

· Team members are restricted from bringing their own equipment, and insufficient equipment supply may hinder project development.

· Team members are restricted to bringing only the analysts of the team to China. This might affect the project development if more people are needed or the required skills are not available.

· The majority of the Chinese population does not have or have a limited access to the Internet.

Provide a general description of any other items that will limit the developer's options for designing the system.

These can include:

(1) Regulatory policies

(2) Hardware limitations; for example, signal timing requirements

(3) Interface to other applications

(4) Parallel operation

(5) Audit functions

(6) Control functions

(7) Higher-order language requirements

(8) Signal handshake protocols; for example, XON-XOFF, ACK-NACK.

(9) Criticality of the application

(10) Safety and security considerations

2.5 Assumptions and Dependencies.

List and describe each of the factors that affect the requirements stated in the SRS. These factors are not design

constraints on the software but any changes to them can affect the requirements in the SRS. For example, an

assumption might be that a specific operating system will be available on the hardware designated for the software

product. If, in fact, the operating system is not available, the SRS would then have to change.

3. Specific Requirements.

This section of the SRS should contain all the details the software developer needs to create a design. This is

typically the largest and most important part of the SRS.

(1) The details within it should be defined as individual specific requirements, following the guidelines for sound

requirements (verifiable, unambiguous, etc.)

(2) Specific requirements should be organized in a logical and readable fashion.

(3) Each requirement should be stated such that its achievement can be objectively verified by a prescribed

method.

(4) Sources of a requirement should be identified where that is useful in understanding the requirement.

(5) One way to classify the specific requirements is as follows:

(a) Functional Requirements

(b) Performance Requirements

(d) Attributes

(e) External Interface Requirements

The best organization for this section depends on the application area and the nature of the software product being

specified. Tables 1 through 4 at the end of this template show four possible organizations.

(1) In Table 1, all the Functional Requirements are specified, then the four types of interface requirements are

specified, and then the rest of the requirements are specified.

(2) Table 2 shows the four classes of interface requirements applied to each individual Functional Requirement.

This is followed by the specification of the rest of the requirements.

(3) In Table 3, all of the issues addressed by the Functional Requirements are specified, then the other

requirements that apply to them are specified. This pattern is then repeated for each of the External Interface

Requirement Classifications.

(4) In Table 4, the interface requirements and the rest of the requirements are specified as they pertain to each

Functional Requirement.

The organization of this section of the SRS should be chosen with the goal of properly specifying the requirements in

the most readable manner. The template outline that follows uses an organization like Table 1.

3.1. Functional Requirements.

This subsection of the SRS should specify what is to be done by the product, to what level or specific requirement,

what inputs should be transformed to what outputs (not how this is done), what specific operations are required.

Where the rationale for a requirement is not obvious, provide an explanation. Where issues need to be resolved, cite

those.

For each function, specify requirements on inputs, processing, and outputs. These are usually organized with these

four subparagraphs:

(1) Purpose of the function: Provide rationale to clarify the intent of the function.

(2) Inputs: sources, valid ranges of values, any timing concerns, operator requirements, special interfaces

(3) Operations to be performed: validity checks, responses to abnormal conditions, types of processing required

(4) Outputs: destinations, valid ranges of values, timing concerns, handling of illegal values, error messages,

interfaces required

For example, the following might be an example specification. Depending on the level of tracking required by the

project, one might trace each of the components of 3.1.1 as separate requirements, or one might trace just 3.1.1. Note

that the level of detail here tells what needs to be accomplished against what specific goals, but it does not specify

how that is to be done.

3.1. Provider Terminal (PT) Functional Requirements

3.1.1. Signature Verification

Purpose: The PT shall have a signature recognition system that can be used to authenticate users of the ChocAn

membership services.

Inputs: Members sign their name once when applying for membership. Each authentication effort done when a

service is requested should take no more than one signature by the member.

Processing: Handling of the authorization should take no more than 5 seconds.

Outputs: If the match is successful, a positive acknowledgment must come to the member at the signature capture

device as well as to the PT. If the match is unsuccessful, an appropriate message to that effect must be

provided to both the capture device and the PT.

3.2. External Interface Requirements

3.2.1 User Interfaces.

This should specify:

(1) The characteristics that the software must support for each human interface to the software product. For

example, if the user of the system operates through a display terminal, the following should be specified:

(a) Required screen formats

(b) Page layout and content of any reports or menus

(d) Availability of some form of programmable function keys.

(2) All the aspects of optimizing the interface with the person who must use the system. This may simply

comprise a list of do's and don'ts on how the system will appear to the user.

3.2.2. Hardware Interfaces.

Specify the logical characteristics of each interface between the software product and the hardware components of

the system. Include such matters as what devices are to be supported, how they are to be supported, and protocols.

3.2.3. Software Interfaces.

Specify the use of other required software products (for example, a data management system, an operating system, or

a mathematical package), and interfaces with other application systems .

For each required software product, the following should be provided:

(1) Name

(2) Mnemonic

(3) Specification Number

(4) Version number

(5) Source

For each interface:

(1) Discuss the purpose of the interfacing software as related to this software product.

(2) Define the interface in terms of message content and format. It is not necessary to detail any well-documented

interface, but a reference to the document defining the interface is required.

3.2.4. Communications Interfaces.

Specify the various interfaces to communications such as local network protocols, etc.

3.3. Performance Requirements.

This subsection should specify both the static and the dynamic numerical requirements placed on the software or on

human interaction with the software, as a whole.

(1) Static numerical requirements may include:

(a) The number of terminals to be supported

(b) The number of simultaneous users to be supported

(d) Sizes of tables and files

Static numerical requirements are sometimes identified under a separate section entitled capacity.

(2) Dynamic numerical requirements may include, for example, the numbers of transactions and tasks and the

amount of data to be processed within certain time periods for both normal and peak workload conditions.

All of these requirements should be stated in measurable terms, for example, 95% of the transactions shall be

processed in less than 1 s, rather than, operator shall not have to wait for the transaction to complete.

Note: Numerical limits applied to one specific function are normally specified as part of the processing

subparagraph description of that function.

3.4. Design Constraints.

Design constraints can be imposed by other standards, hardware limitations, etc.

3.4.1. Standards Compliance.

Specify the requirements derived from existing standards or regulations. They might include:

(1) Report format

(2) Data naming

(3) Accounting procedures

(4) Audit Tracing. For example, this could specify the requirement for software to trace processing activity.

Such traces are needed for some applications to meet minimum government or financial standards. An audit

trace requirement might, for example, state that all changes to a payroll data base must be recorded in a trace

file with before and after values.

3.4.2. Hardware Limitations.

Identify the requirements for the software to operate inside various hardware constraints.

3.5. Quality Characteristics.

There are a number of quality characteristics that can apply to software. Pick the ones most important to this product

and develop a section for each one.Definitions of the quality characteristics follow.

• Correctness - extent to which program satisfies specifications, fulfills user’s mission objectives

• Efficiency - amount of computing resources and code required to perform function

• Flexibility - effort needed to modify operational program

• Integrity/security - extent to which access to software or data by unauthorized people can be controlled

• Interoperability - effort needed to couple one system with another

• Maintainability - effort required to locate and fix an error during operation

• Portability - effort needed to transfer from one h/w or s/w environment to another

• Reliability - extent to which program performs with required precision

• Reusability - extent to which it can be reused in another application

• Testability - effort needed to test to ensure performs as intended

• Usability - effort required to learn, operate, prepare input, interpret output

3.5.1. xxx

Describe the rationale for including this characteristic for this product.

Describe how the presence, absence, or level of this characteristic will be measured; identify ways to test the

characteristic once the product is complete.

3.5.2. yyy.

etc.

3.6. Other Requirements.

Certain requirements may, due to the nature of the software, the user organization, etc., be placed in separate

categories such as those below.

3.6.1. Data Base.

This could specify the requirements for any data base that is to be developed as part of the product. This might

include:

(1) Types of information

(2) Frequency of use

(3) Accessing capabilities

(4) Data element and file descriptions

(5) Relationship of data elements, records and files

(6) Static and dynamic organization

(7) Retention requirements for data

Note: If an existing data base package is to be used, this package should be named under Interfaces to Software and

details of using it specified there.

3.6.2. Operations.

This could specify the normal and special operations required by the user such as:

(1) The various modes of operations in the user organization; for example, user-initiated operations

(2) Periods of interactive operations and periods of unattended operations

(3) Data processing support functions

(4) Backup and recovery operations

Note: This is sometimes specified as part of the User Interfaces section.

3.6.3. Site Adaptation Requirements.

This could:

(1) Define the requirements for any data or initialization sequences that are specific to a given site, mission, or

operational mode, for example, safety limits.

(2) Specify features that should be modified to adapt the software to an installation.

4. Supporting Information.

The supporting information; that is, the Table of Contents, the Appendices, and the Index, make the SRS easier to use.

The Appendices are not always considered part of the actual requirements specification and are not always

necessary. They might include:

(a) Sample I/O formats, descriptions of cost analysis studies, results of user surveys.

(b) Supporting or background information that can help the readers of the SRS.

(d) The history, background, experience and operational characteristics of the organization to be supported.

(e) A cross-reference list, arranged by milestone, of those incomplete software requirements that are to be

completed by specified milestones.

(f) Special packaging instructions for the code and the media to meet security, export, initial loading, or other

requirements.

(3) When Appendices are included, the SRS should explicitly state whether or not the Appendices are to be

considered part of the requirements.