The upper section of the work breakdown structure (WBS) should identify the major phases and milestones of the project in a summary fashion. In addition, the upper section should provide an overview of the full scope and timeline of the project and will be part of the initial project description effort leading to project approval. The middle section of the WBS is based on the seven systems development life cycle phases as a guide for WBS task development. The WBS elements should consist of milestones and "tasks" as opposed to "activities" and have a definitive period (usually two weeks or more). Each task must have a measurable output (e.x. document, decision, or analysis). A WBS task may rely on one or more activities (e.g. software engineering, systems engineering) and may require close coordination with other tasks, either internal or external to the project. Any part of the project needing support from contractors should have a statement of work (SOW) written to include the appropriate tasks from the SDLC phases. The development of a SOW does not occur during a specific phase of SDLC but is developed to include the work from the SDLC process that may be conducted by external resources such as contractors.
* The skin of all species is a syncitium, a layer of cells that shares a single external membrane.
* Trematodes are divided into two groups, Digenea and Aspidogastrea (also known as Aspodibothrea).
Baselines
Baselines are an important part of the systems development life cycle. These baselines are established after four of the five phases of the SDLC and are critical to the iterative nature of the model .[13] Each baseline is considered as a milestone in the SDLC.
functional baseline: established after the conceptual design phase.
allocated baseline: established after the preliminary design phase.
product baseline: established after the detail design and development phase.
updated product baseline: established after the production construction phase.
* However, a few are internal parasites. Adult monogeneans have large attachment organs at the rear, haptors (Greek haptein, means "catch"), which have suckers, clamps, and hooks.
* They often have flattened bodies. In some species, the pharynx secretes enzymes to digest the host's skin, allowing the parasite to feed on blood and cellular debris. Others graze externally on mucus and flakes of the hosts' skins. The name "Monogenea" is based on the fact that these parasites have only one nonlarval generation.
History
The product life cycle describes the process for building information systems in a very deliberate, structured and methodical way, reiterating each stage of the product's life. The systems development life cycle, according to Elliott & Strachan & Radford (2004), "originated in the 1960s, to develop large scale functional business systems in an age of large scale business conglomerates. Information systems activities revolved around heavy data processing and number crunching routines".[6]
Several systems development frameworks have been partly based on SDLC, such as the structured systems analysis and design method (SSADM) produced for the UK government Office of Government Commerce in the 1980s. Ever since, according to Elliott (2004), "the traditional life cycle approaches to systems development have been increasingly replaced with alternative approaches and frameworks, which attempted to overcome some of the inherent deficiencies of the traditional SDLC".[6]