Effort required to couple one system with another is called:

Interoperability is the software quality attribute that defines the degree to which two or more systems or components can exchange information and use that information. The "effort required to couple one system with another" is a direct, inverse measure of this attribute. A system with high interoperability requires minimal effort to integrate with other systems, as it likely adheres to standard communication protocols and data formats. This characteristic is crucial for modern, distributed systems and is a sub-characteristic of "Functional Suitability" in the ISO/IEC 25010 software quality model.

A. Maintainability: Refers to the ease of modifying a single system to correct faults or improve it, not connecting it to other systems.

B. Flexibility: Concerns the ease of adapting a system for different purposes or environments, a broader concept than system-to-system coupling.

C. Usability: Relates to the ease with which a human user can interact with the system, not how systems interact with each other.

1. ISO/IEC 25010:2011, Systems and software engineering — Systems and software Quality Requirements and Evaluation (SQuaRE) — System and software quality models. In the Product Quality Model described in section 4.2, Interoperability is defined as the "Degree to which two or more systems, products or components can exchange information and use the information that has been exchanged."

2. Pressman, R. S., & Maxim, B. R. (2020). Software Engineering: A Practitioner's Approach (9th ed.). McGraw-Hill. In Chapter 15, "Software Quality Assurance," the text discusses quality attributes. Interoperability is described as the ability of a system to communicate and cooperate with other systems, which directly relates to the effort of coupling them.

3. Lau, L. (2017). Lecture Notes: Software Quality. Department of Computer Science and Engineering, The Chinese University of Hong Kong. In lectures on Software Quality Models (e.g., McCall's, ISO 9126/25010), Interoperability is consistently defined as the effort required for one system to link with another. (Referencing typical content from such university courseware).