More than forty years have passed since the early attempts to model projects. A large domain of theoretical developments has grown producing a high number of analytical and numerical results, but it seems that the main model is still the same: the concept of project network. This concept has come to represent the two major features underlying the notion of a project: the sequential and the competitive nature of its components, the project's activities. Actually, the sequential property defines the structure of the project and the competitive nature stems from the use of common resources (facilities, goods, equipment, management, etc.) to carry out the different activities. However, significant advances have been achieved in project modelling, allowing the production of much more powerful results: A. the concept of precedence and the description of activities has been generalized to produce a wide range of realistic representation of projects. B. the stochastic study of the features of projects such as the duration and cost of their activities is carried out by several analytical and numerical models, allowing experimental and forecasting analyses. C. the allocation of resources can be now studied for more complex situations and restrictions. D. the financial description of projects is more accurately studied and its optimization is thoroughly pursued. E. the assessment and the evaluation of projects now can be studied within the framework of multicriteria decision theory considering multiple perspectives and supporting the project manager to select the most appropriate compromises between risk, time and expected gains.

Luis Valadares Tavares is Professor of Operational Research and Systems Engineering at IST - Technical University of Lisbon, Portugal, as well as President of IST's Center for Urban and Regional Systems and of the Portuguese eBusiness Society.

1. A Systemic Introduction to Project Management.- 1. Projects and organizations.- 2. Project management and model building.- 3. The general systemic model.- 4. The systemic model of project management.- 2. Basic Models for Project Management.- 1. Project networking.- 2. Sequentiality.- 3. Resources.- 4. Duration.- 5. Optimal scheduling.- 3. Structural Modelling of Projects Networks.- 1. Hardness and complexity.- 2. Modular decomposition.- 3. Network reduction.- 4. Hierarchical levels.- 5. Level adjacency matrix.- 4. Morphology and Simulation of Project Networks.- 1. Morphology.- 2. The generation method.- 3. Comparative analysis.- 4. A test set of generated networks.- 5. Duration of projects.- 1. Modelling.- 2. Experimental results.- 6. Scheduling of Project Networks.- 1. General formulation and typology.- 2. The binary formulation.- 3. The heuristic optimization of the binary model.- 4. The proposed non-linear continuous model.- 5. An application of the proposed model using RISKNET and GAMS-MINOS.- 6. Dynamic Programming.- 7. Risk.- 7. The Assessment and Evaluation of Projects.- 1. Typology.- 2. Financial assessment and evaluation.- 3. Multi-criteria assessment or evaluation.- 4. The MACMODEL.- 8. The Optimal Scheduling of a Project in Terms of Its Duration.- 1. The synthesis of decision variables.- 2. A theorem on the propagation of floats.- 3. The developed stochastic model of the project network.- 4. The results.- 5. Conclusions.- Annex 1 - Developed Software.- 1. RISKNET.- 2. MACMODEL.- Annex 2 - Main Notation.- References.