So it is today. Schedule disaster, functional misfits, and system bugs all arise because the left hand doesn't know what the right hand is doing. As work （）, the several teams slowly change the functions, sizes, and speeds of their own programs, and they explicitly or implicitly （ ） their assumptions about the inputs available and the uses to be made of the outputs.For example, the implementer of a program-overlaying function may run into problems and reduce speed relying on statistics that show how （ ） this function will arise in application programs. Meanwhile, back at the ranch, his neighbor may be designing a major part of the supervisor so that it critically depends upon the speed of this function. This change in speed itself becomes a major specification change, and it needs to be proclaimed abroad and weighed from a system point of view.How, then, shall teams （ ） with one another? In as many ways as possible.Informally. Good telephone service and a clear definition of intergroup dependencies will encourage the hundreds of calls upon which common interpretation of written documents depends.Meetings. Regular project meetings, with one team after another giving technical riefings, are （ ）. Hundreds of minor misunderstandings get smoked out this way.Workbook. A formal project workbook must be started at the beginning.
The entity-relationship (E-R) data model is based on a perception of a real world that consists of a clletion of basic objects, called( ) ，and of relationships among these objects.An entity is a“thing”or "object" in the real world that is distinguishable from other objects.Entities are described in a database by asetof() : A relationship is an association among several entities. The set of all entities of the same type and the set of all relationships of the ametype are termed an entity sct and relationship set, respectively. The overall logical structure (schema) of a database can be expressed graphically by an E-R diagram, which is built up from the fllowing components:( ) represent entity set,( ) represent atributes, ete. In addition to entities and relations, the E-R model represents certain( )to which the contents of a database must conform. The entity-relationship model is widely used in database design.
In the fields of physical security and information security, access control is the selective restriction of access to a place or other resource. The act of accessing may mean consuming,entering, or using. Permission to access a resource is called authorization（授权）.An access control mechanism（请作答此空）between a user （or a process executing on behalf of a user） and system resources, such as applications, operating systems, firewalls; routers, files,and databases. The system must first authenticate（验证）a user seeking access. Typically the authentication function determines whether the user is （ ） to access the system at all.Then the access control function determines if the specific requested access by this user is permitted. A security administrator maintains an authorization database that specifies what type of access to which resources is allowed for this user. The access control function consults this database to determine whether to（ ） access. An auditing function monitors and keeps a record of user accesses to system resources.In practice, a number of（ ）may cooperatively share the access control function. All Operating systems have at least a rudimentary（基本的）.and in many cases a quite robust, access control component. Add-on security packages can add to the （ ）access control capabilities of the OS. Particular applications .or utilities, such as a database management system, also incorporate access control functions. External devices, such as firewalls, can also provide access control services .
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