This paper presents the concept of a new metadata type, defined as procedural metadata, which enhances automation and interoperability of the web of things. As data-driven days have arrived, data has become ubiquitous, and it is considered as a new valuable asset for the fourth industrial revolution. Accordingly, systems and services are expected to intelligently make decisions and perform tasks by interacting with environments through sensing and actuation. This requires accumulated knowledge of procedures to be described in human and machine-readable ways. Procedural metadata is proposed as the means to provide the common descriptions on composable procedures of not only individual devices but also smart systems as a whole, based on existing data models and ontologies. As a type of metadata, procedural metadata does not affect the original formats, models, vocabularies, ontologies, etc. of data, devices, and systems. However, it rather provides additional information on common descriptions of logic and workflows to make decisions and perform tasks. This paper describes the proposed concept with examples, principles, and discussions. For a proof of concept it is implemented in Matlab based on a scenario analysis in a smart home environment. Then, its potential and feasibility to be applied to the web environment are given.