Tabular Expressions Based Formal Documentation Of Requirement And Supporting Tool

Along with the expansion of the software systems, gradually people recognized that the Requirements Analysis is not only the initial stage of the software development, but also the key phase which runs through the whole life cycle. However, through the industry experience over a long period of time, it had been proven that the wrong requirements definition is the first leading cause of the failures of the software projects. DDSD (Document Driven Software Development) emphasizes that there must be series of integrated, strict, precise documents with well mathematical-definition, and the documents should support the consistency validation. Tabular Expressions is a formal specification method which defines mathematical functions or relations in tabular form. TE not only has the preciseness and accuracy of the mathematics, but also has the well readability. TE provides very good support for DDSD.Precise documents-centered DDSD provides a good solution for the Requirement Engineering. However, because of the complexity of large software system and the huge requirements text, there is a gap between the original informal requirements and the precise formal documents. Meanwhile, it is also hard to ensure the completeness and the consistency.AORE (Aspect Oriented Requirement Engineering) centering on"Separation of Concerns"introduces the concept of concerns in requirement phase. Through the identification and definition of concerns in requirements text, AORE led to a great drop in the complexity and coupling of the system, effectively improved the extent of the modularization and built a bridge between the text and the formal documents.Hence, we should combine the advantages of the AORE and DDSD. It is very valuable to give a method which could draw the informal and formal requirements together.As a key part of the requirements management, requirements changes have a tremendous impact on the success of the software projects. Effective requirements changes impact analysis could give the accurate estimation of the system, and provide the valuable information to project manager. In this paper a PageRank algorithm based method of requirement change impact analysis is given. The process applies the PageRank algorithm to the formal requirements model of a system and conducts the environment variable impact analysis.The main work of this thesis is as follows:1. Give a process of formal documentation of requirements, through analyzing the contents of the requirement documents, the Four Variable Model and the AORE theory. Through constant refining the process transforms the informal requirements text to the integrated, precise formal requirements documents. The main process is as follows: (1) Analyzing the labeled textual requirement statements and eliciting concerns, then specifying concerns and their relationships. (2) Identifying kinds of variables and defining them. (3) According to the concern relationships and the shared labeled requirements between variables, identifying and defining the variable relationships. (4) Based on the previous formal definition, specifying the formal documents by the TE tool, and conducting essential validation. Some crucial parts are interpreted as follows:a) Concerns elicitation. Through reading and analyzing the textual requirements, some meaningful keywords will be identified and some of them could be abstracted as concerns and formally defined. Meanwhile, with analyzing the shared requirements of the concerns, concerns relationships could be specified and then the concern relationship graph could be built.b) Variables definition and classification. The key of the requirement documents specification of the computer systems is to elicit the related environment elements. For each concern and the requirements it resides, some variables will be defined and classified as monitored, controlled, input, output, user-defined.c) Variable Dependency Graph definition. According to the concern relationship graph, dependencies between variables could be identified and defined after analyzing the calling of the concern modules. Then the process conducts the filtration to the dependency candidates according to the sort of variables and gives the formal model of variable dependency Graph.d) Formal Documents specification. A integrated formal requirement documents include the definition of some relations, such as REQ, NAT, IN, OUT, SOF. Each relation could be defined as functions of the variables in Four Variable Model, in other words, the tabular expressions. After the above-mentioned formal definition, formal documents could be defined. When defining the expressions of variable v, the formal information of v and the dependency information of v will be necessary. With those information, the formal documents could be finally specified by the TE Tool.2. In this thesis, a PageRank algorithm based approach of requirement change impact analysis has been given. First, a modified PageRank algorithm will be applied to the variables dependency graph, which produces quantitative assessment of each formal variable on the whole system; then, an impact estimation will be conducted on the variable level. The main process and some necessary interpretation are as follows:a) Requirements modeling of system: According to the process of the formal documentation, modeling the requirements of the goal system.b) Assigning weights to variable dependencies: In this paper a weight assignment method has been given, which specifies the dependency with kernel variables and dominant requirements. Then some particular dependencies could get higher rank scores and the results are effectively optimized.c) Applying PageRank algorithm to the variable dependency graph: Original PageRank algorithm has been modified and applied to the variable dependency graph to calculate rank score for each variable.d) Change impact analysis. Based on the result and the variable dependency graph, three kinds of impact analysis have been conducted in this thesis: based on variables, based on labeled requirements and based on dependencies.In summary, a formal documentation of requirements approach and a PageRank algorighm based requirement impact analysis have been introduced, which resolve the problems of the complexity system documentation and requirements impact analysis. A formal documentation tool set has been implemented based on the C sharp language and .NET framework.