First generation: Technology push
The first generation models of innovation, so called technology push models, are simple linear models developed in the 1950s (Figure 1), which treated innovation as a sequential process that took place in discrete stages.

Figure 1: First generation technology push model (Rothwell, Towards the fifth-generation innovation process, 1994)

For Hobday (Hobday, 2005), first generation models assume that scientific research and discovery stimulates and ‘pushed’ technological innovation with applied research, engineering, manufacturing and marketing representing the proceeding steps. As Rothwell argues, first generation models were typically deployed to rationalise additional R&D spending to produce greater innovation output. In critiquing the model, Rothwell (Rothwell, Towards the fifth-generation innovation process, 1994) identifies that little attention was paid to the transformation process itself or to the role of the marketplace in the process.
Second generation: Demand/market pull
In this generation (Mid 1960s to early 1970s) a linear model of innovation also applies, this time acknowledging the importance of market demand for products. In the context of growing competition in the marketplace and the pursuit of market share, this model recognized demand side factors (sometimes described as the “need-pull”) (Hobday, 2005).

Figure 2: Second generation market pull model (Rothwell, Towards the fifth-generation innovation process, 1994)

In contrast to the preceding first generation model, this model stresses the role of the marketplace and market research in identifying and responding to customer needs, as well as directing R&D investments towards these needs. Therefore, the role of R&D was to meet market demands as opposed to discovery.
Third generation: Coupling/Interactive
Empirical innovation studies conducted during the 1970s highlighted that linear models reflected atypical and extreme conceptualizations of innovation, as the process is actually characterized by the interaction and coupling of science and technology and the marketplace (Mowery & Rosenberg, 1978). The coupling model presented in Figure 3, adopts a coupling process, overcoming many of the shortcomings of the previous extreme linear models, by building in interaction and feedback loops between drivers and functions within the firm. The emphasis within this model is on the system of relations both within the organization (particularly between R&D activities and the other departments), and beyond the organization (for example, the customer and supplier relations that will inform innovation). Rothwell notes that the process of interaction was not necessarily continuous but could be understood in terms of functionally interacting and interdependent stages, involving intra- and inter-organisational linkages (Hobday, 2005).

Figure 3: Third generation coupling/interactive model (Rothwell, Chair Hydro—Quebec Conference enGestion de al Technologie, 1993)

Figure 3: Third generation coupling/interactive model (Rothwell, Chair Hydro—Quebec Conference enGestion de al Technologie, 1993)
Fourth generation: integrated
While third generation models represent non-linear depictions of the innovation process with feedback loops, their predominant sequential nature surfaced criticism. In response, the fourth generation of innovation modelling (Figure 4) focuses attention on parallel, simultaneous and integrated development approaches influenced by learning from Japanese leadership in such areas as JIT strategies and production efficiencies, and also the recognition of the need for supplier integration, linkages and alliances to cope with shortening product lifecycles.

Figure 4: Fourth generation integrated model (Rothwell, Chair Hydro—Quebec Conference enGestion de al Technologie, 1993)

Fourth Generation Models therefore seek to capture and reflect cross functional integration within firms, and in the external environment incorporating stakeholders ranging from suppliers, customers, universities and government agencies (Hobday, 2005).

Fifth generation: Networking and systems integration
Fifth generation of innovation models are characterised as being based on overall organizational and systems integration and networking (SIN) perspective. The dominant characteristics of this generation of modelling are the influence of external environment and the effective linkage and communication with external stakeholders (du Preez & Louw, 2008). For Hobday, innovation is a distributed networking process and observations during the 1980s and 1990s of increased corporate alliances, partnerships, R&D consortia and joint ventures supported this viewpoint. Accepting that innovation happens within a network of internal and external actors the network model presented in Figure 5 indicates the importance of networking potential across all aspects of innovation.

Figure 5: Network model of innovation (Trott, 2005)

In essence, the fifth-generation models acknowledge the best practice notions from previous generation models of pursuit of strategic networking, and surmounting the importance of the speed of development and speed-to-market. For Rothwell, fifth generation process rely on the use of information technology systems and tools to expedite the speed and efficiency of innovation development across the entire network of innovation, spanning internal functions and external collaborators. Galanakis’s creative factory concept, using a systems thinking approach represents a model of networked systems perspective (Figure 6). At the center of this model is the enterprise which is the generator of innovations and this is surrounded by three core innovation processes: (1) the knowledge creations process from research, (2) the transformational development process and (3) product success in the market. Moreover, reflecting the systems perspective, the innovation process is affected by internal factors of the firm and equally so external factors in the National Innovation Environment.
Figure 6: Systems innovation model (Galanakis, 2006)

Sixth generation: open innovation
Extending the networking perspective introduced in the previous model structure, the sixth generation of innovation models represent open innovation. The model whereby enterprises invest exclusively in research and development departments to drive innovation is eroding with the advent of open innovation. In contrast to closed innovation, where innovation activities take place entirely within one firm, open innovation (Figure7) processes are characterized as spanning firm boundaries presenting opportunities to commercialize both external ideas and internal ideas externally.
(Chebrough, 2003) describes open innovation as paradigm shift whereby competitive advantage can result from leveraging discoveries beyond the confines of a single internal R&D unit (inbound open innovation) and can equally benefit from relying exclusively on their own internal paths to market through engaging with external organisations that may be better positioned to commercialise a given technology (outbound open innovation). In a similar vein, (Enkel, et al., 2009) identifies three core processes can be differentiated in open innovation:
Figure 7 Open Innovation Model 

Source: (Chesbrough, 2004)

As the IPACSO core innovation process leans toward the open innovation model, it is important to provide the reader with a brief description of this type of process. Chesbrough (Chesbrough, Open innovation: the new imperative for creating and profiting from technology, 2003) describes open innovation as a paradigm shift whereby an organization can benefit from leveraging discoveries beyond the confines of a single internal R&D unit (inbound open innovation) and can equally benefit from engaging with external organizations that may be better positioned to commercialize a given technology (outbound open innovation). Three core processes can be identified in open innovation:

1. The outside-in process: this process involves enhancing and extending an enterprise’s own knowledge base through the integration of suppliers, customers, and external knowledge sourcing. Crowdsourcing is an example of an outside-in process. 
2. The inside-out process refers to securing commercial/revenue benefits by bringing ideas to market faster than internal development via licensing IP and/or multiplying technology, joint ventures, and spin-offs. Corporate venturing activities are an example of an inside-out process. 
3. The coupled process refers to co-creation with partners through alliances, cooperation, and reciprocal joint ventures to combine the outside-in process (to gain external knowledge) with the inside-out process (to bring ideas to market). Co-creation is widely studied in the open innovation literature.