Each core resource can be used to generate a relative advantage over rival firms. Such core resources are amenable to process improvements and technology substitutes, thus opening up opportunities for improved competitive performance. A key focus in understanding core resources is to determine which core resources are significant to a company's competitive performance. 
The core resource view introduced by Barneys is most often associated with an organizational-level concept of competitive advantage and is the most complete and enduring concept of competitive advantage available. The resource-based view regards core resource competencies as both a challenge and an opportunity. The challenge comes from managing differences in resource capabilities among competing firms; the opportunity comes from identifying core resources to ameliorate those differences in capabilities and ultimately differentiate the product line of one firm relative to those of others. A key assumption is that all firms have a mixed set of core competencies, some of which may be common, but others unique.
There are perhaps three commonly used ways to define core competencies: 1) competencies based on actual resources, 2) competencies that are tangible or intangible and 3) competencies that increase the competence of managers. The general consensus is that core competencies must be formulated using various forms of evidence and judged based on their viability, stability, desirability and independence. Core competences are to be differentiated by broad qualities that reflect the relative capabilities of firms to offer their products to the market.
However, many strategists still have difficulty articulating the core competencies, and Barney expresses some of the concerns that are often raised by managers who are making their core competences decisions. For example, many firms have core competencies in market research (which often get overlooked because they have less decisive value); sales (which are often overlooked because they are not as unique as core marketing capabilities); and technology (which can easily be imitated by rivals). d2c66b5586