First, the demand for classification and presentation:
(A) demand the strict sense of the common classification of the following five:
1. functional requirements (functional requirement): The main system and related requirements, namely, without considering the physical constraints, users want to be able to perform the activities.
2. Performance requirements (performance requirement): overall system performance characteristics or other parts should have.
3. The quality attributes (quality attribute)
4. The external interface (external interface): software, hardware, database interface.
5. constraint (constraint): such as programming languages, hardware facilities.
(B) a detailed description of the five kinds of needs:
1. Functional Requirements:
Software requirements of the most common and most important needs, but also the most complex needs.
2. Performance requirements common categories:
( 1) speed: System time required to complete the task.
( 2 ) capacity ( Capacity): the amount of stored data.
( 3 ) the throughput ( throughput): number of transactions completed in a continuous time.
( 4 ) load ( Load ) : concurrent workload bearer.
( 5 ) real-time ( Time-Critical)
3. Quality attributes:
In order to measure the quality of the system, the need to use some of the quality factors quantized establish quality characteristics. The book describes [ISO / IEC 9126-1], [ IEEE 1061-1992,1998] two qualities models, both substantially free from consistency, only slightly different sub-factors refinement features included. Below [IEE 1061-1992,1998] an example to summarize, the main contains the following elements:
( 1 ) Functional
Completeness of the system, correctness, security, compatibility and interoperability.
( 2 ) Reliability
No defects of the system, fault tolerance, availability.
( 3 ) ease of use
It contains understandable, easy to learn, easy operability of communication.
( 4 ) Efficiency
It contains time economy, resource economy.
( 5 ) Maintainability
It contains amendments, scalability, testability.
( 6 ) Portability
Independence comprising hardware and software can be installed, reusability.
4. External Interface:
Hardware and software of the system interfaces should be noted the following:
( 1 applications) interface
( 2 ) the input-output interface
( 3 ) format specification, such as data, command format
( 4 ) Exception Handling requirements
5. Constraints:
Common constraints content:
( 1 ) system development and runtime environment
( 2 ) the problem domain relevant standards: including laws and regulations, trade agreements and firm size and so on.
( 3 ) business rules
( 4 ) social factors: for example, culture, religion.
6. Other requirements:
For example, installation requirements, training needs, data requirements and so on.
Second, the characteristics of good demand
(A) Completeness
You do not need to do more to expand the system will be fully functional description of user needs. In requirements development process, for no clear information can be marked as TBD (To be Determined, to be determined), but before the end of the development process, all TBD must be resolved.
Can to protect the completeness requirements described in different ways by different types of needs.
1. functional requirements need to ensure that the following are described:
( 1 ) Behavior of those trigger ( Trigger): it makes the system behavior needs to perform the functions, including data input by a common trigger, request received, abnormality to be treated.
( 2 pre-conditions) behavior ( pre-for condition Condition): system successfully meet the functional requirements of the premise. Common conditions include pre-mode or state of the system, the state of other external systems, any value of the system data.
( 3 ) behavior: behavior under the pre-conditions are triggered received, the system must perform.
( 4 ) post-condition ( POST-for condition Condition): a state in which the behavior of the system is successfully executed.
( 5 ) does not satisfy the preconditions, the results of the corresponding situation.
(B) the correctness
(C) feasibility
(D) the need
(E) unambiguous
(F) Verifiable
Issue Date: 2018-03-25 14:17