Systems, devices, and stored, machine-interpretable instruction sets for the secure, collaborative, efficient, and convenient processing of transaction data, and methods of using them. The invention may be particularly useful for building data sets useful in the purchase, sale, leasing, or other transfer of rights in products, services, and real and intangible properties. Through the use of specifically-assigned persistent resource locators, users are enabled to build individual and group transaction data sets that may be associated with variable levels of access to group and non-group members. When users have established desired transaction data sets, they can optionally execute simultaneously one or more related transactions. Data generated by such processes can be used in conjunction with predictive analytics processes in order to improve transaction building processes and user experiences.