1 Abstract—The web services applications for digital reference service (WSDRS) of LIS model is an informal model that claims to reduce the problems of digital reference services in libraries. It uses web services technology to provide efficient way of satisfying users’ needs in the reference section of libraries. The formal WSDRS model consists of the Z specifications of all the informal specifications of the model. This paper discusses the formal validation of the Z specifications of WSDRS model. The authors formally verify and thus validate the properties of the model using Z/EVES theorem prover. Keywords—Validation, verification, formal, theorem proving. I. INTRODUCTION ORMAL proving is the act of showing the correctness of a system with respect to a certain formal specification or property using mathematical methods. After the formal model of a program is built, a variety of properties can be validated over it. The formal specification of a system can also be verified to ensure its correctness and to prove its consistency and completeness using formal verification techniques before system design and implementation [1], [3]. Formal proving is a complete argument of mathematical representation and it is used to validate statement about system description. Usually, formal proving can be done manually or automatically using formal method tools such as theorem provers. Developers usually cover a long time while performing the theorem proving process, so there might be a great possibility of mistakes. The proofs are efficient when presented in a user-friendly approach and not in an unreasonable large size. However, a lot of the proofs that are involved in software validation are naturally detail, low-level and repetitious. So we can briefly state that it is unsuitable for human checking. Thus, formal proving supported by tool, do not only reduce the possibility of mistakes but also removes it totally. Hence, the use of support tool is a main factor that can affect the acceptance of formal method practically [1]. The Z specification language is a way of decomposing a specification into small pieces called schemas. Each piece can be linked with comments that give informal explanation about the importance of the formal mathematics. A schema is essentially the formal specification analogous to programming language subroutines that are used to structure a system, Zainab Musa Magaji is with the Universiti Sultan Zainal Abidin, Malaysia (e-mail: zeemusa5@gmail.com). where the schemas are used to structure a formal specification. The Z is physically powerful on sets and functions. Generally, Z notation is use for sequential situation and model-based specification. It combines formal and informal description and uses graphical highlighting when presenting specifications [2], [7]. In this paper, we validate the Z specifications of WSDRS model by using theorem proving technique based upon two aspects: the initial state and the pre-conditions. Validation of the initial state is to show that the Z specifications developed were consistent. While the validation of the pre-conditions is to show that the z specifications developed were complete, consistent and were applied in the right domain. In order to implement the validation process, a few theorems will be developed for both aspects. Each theorem will be checked using Z/EVES theorem prover tool. The tool will help in reducing time, energy and mistakes compared to manual theorem proving which can be error full and tedious. II.THEOREM PROVING (DEDUCTIVE VERIFICATION) Theorem-proving means that systems satisfy their specification, which given by temporal Logic formulas, using deductive (i.e. theorem proving) methods. It involves generating a collection of mathematical proof obligations from a system and its specifications, the truth of which imply conformance of the system to its specification, and discharging these obligations using theorem provers such as interactive theorem provers, automatic theorem provers, satisfiability modulo theories (SMT) solvers. This approach requires the user to understand in detail why the system works correctly, and to convey this information to the verification system, either in the form of a sequence of theorems to be proved or in the form of specifications of system components (e.g. functions or procedures) and subcomponents (such as loops or data structures) [4]. These techniques are not fully automatic and require user interaction and the effective guidance of a theorem-proving tool. It is the most powerful and least restricted verification technique because it can prove anything [5]. Theorem-provers are softwares that help in solving problems and answering questions that involve reasoning. The assistance can either be interactive, where one instructs the program to draw some conclusions, present them to the user, and then to ask for a new set of instructions; or fully automatic, where the program is assigned an entire reasoning task [5]. Validation of the Formal Model of Web Services Applications for Digital Reference Service of Library Information System Zainab M. Musa, Nordin M. A. Rahman, Julaily A. Jusoh F World Academy of Science, Engineering and Technology International Journal of Computer and Information Engineering Vol:9, No:8, 2015 1959 International Scholarly and Scientific Research & Innovation 9(8) 2015 scholar.waset.org/1307-6892/10002386 International Science Index, Computer and Information Engineering Vol:9, No:8, 2015 waset.org/Publication/10002386