The exchange of knowledge between formal and informal sector can take place at different levels of abstraction:
The most basic level is the artefactual level, i.e. adaptation of form, features, and functions of a product, process, service or institutional design.
The next level is the analogic/metaphorical level implying learning by approximation. Not the exact concept but its derivation in some form or function is drawn upon. For instance bio-mimicry has been applied for self-cleaning surfaces like the lotus leaf.
Learning can also take place through heuristics/principles underlying an innovation. This kind of rule of thumb learning can be used in far wider domains. For example, any plant that is not eaten by cattle or other animals could be a potential source of herbal pesticides.
On a gestalt/configurational level, learning requires looking at a combination of factors responsible for an innovative situation. Such factors could be technological building blocks, institutional arrangements and cultural values. In some parts of the world, people make a bridge by joining roots of the trees growing on two sides of the river. This technology of bridge making requires collective action in the local cultural context. Learning on this level requires a unique combination of different factors contributing to a viable solution.
There are many gaps in our social, institutional and cultural context due to policy or procedural inadequacies. Sometimes, these gaps are also caused by absence of appropriate innovations. Another reason for these gaps could be our inability to adapt frugal solutions available elsewhere in the world to our needs. When these solutions emerge in the informal sector and through the efforts of common people, the barriers to learning from them become even stronger.
Take any one local unmet social or institutional need e.g. with regard to the elderly, children, disabled, unemployed) and try to come up with innovative solutions using one or a combination of the four ways of learning. In case you have another way of learning, you are welcome to use that so long as it helps to find innovative solutions.