IT-SC book: Advanced CORBA Programming with C++ in Software

Print USS Code 39 in Software IT-SC book: Advanced CORBA Programming with C++
IT-SC book: Advanced CORBA Programming with C++
ANSI/AIM Code 39 Encoder In Visual C#.NET
Using Barcode printer for .NET framework Control to generate, create Code 3 of 9 image in Visual Studio .NET applications.
Preferences, which control the order in which service offers are to be returned (see Section 1938) Policies, which control non-functional aspects of a search, such as how many offers to return and whether to return the full description of a service or only the object reference to the service provider (see Section 1939) 1934 Constraint Expressions The most important part of a service request is the constraint expression, which determines the particular tire shops that meet the importer's criteria Constraint expressions (also called queries) are Boolean expressions over the property values of service offers In the simplest case, a constraint expression can be TRUE, in which case any service offer (of the specified type) will match the constraint An example of a more complex constraint is as follows: Find a set of steel radial tires on offer in the San Francisco Bay area with a speed rating of at least 120 mph, size P205/65R15, made by either Bridge-stone or Goodyear Make sure that either Visa or MasterCard is accepted for payment Of course, the actual constraint is expressed not in English but rather in a formal constraint language (see Section 1910) 1935 Federation Federation (or interworking) of traders permits access to very large collections of service offers without the need to store all offers in a single physical database (The idea is analogous to federated naming graphs) Federation is transparent to clients (unless they choose to explicitly take it into account); a federated trader appears to the client as a single logical trader, just as a federated naming graph appears as a single logical graph to clients of the Naming Service Traders are federated by one trader acting as the client to another trader For example, suppose a client submits a service request to trader A Trader A not only searches its own database but also forwards the request to its federated trader B Eventually, trader B returns its results to trader A, which merges them with its own results and then returns the merged results to the client The topology of a trader federation can be arbitrarily complex and is even allowed to contain loops The OMG specification allows federated traders to implement loop detection so that queries from clients are not forwarded from trader to trader indefinitely 1936 Dynamic Properties Normally, the properties in a service offer have a value that is simply stored by the trader This means that the value of a property does not change unless someone explicitly
Painting Code 3/9 In .NET Framework
Using Barcode maker for ASP.NET Control to generate, create Code 3/9 image in ASP.NET applications.
IT-SC book: Advanced CORBA Programming with C++
Code 39 Extended Generator In Visual Studio .NET
Using Barcode printer for .NET Control to generate, create Code 3/9 image in .NET applications.
updates it Such static property values are fine for things such as tire shops because the service being advertised does not change characteristics very often In some situations, however, static properties are inadequate A typical example is trading for shares in a share market In this case, the different shares on offer are the service offers, and the current share price corresponds to one of the properties of each offer The problem is that the share price can fluctuate very quickly If static properties were used to indicate share prices, they would have to be updated frequently (possibly hundreds of times a day) to continually reflect the current price To accommodate such situations, traders offer dynamic properties A dynamic property does not store an actual value for the property Instead, it stores an object reference to an object that can deliver the current value of the property when the trader evaluates a constraint The trader calls an operation on the object to get the current property value Dynamic properties are ideally suited for environments in which property values must reflect rapidly changing information Importers are unaware of whether a property is static or dynamic If an importer asks the trader for the value of a particular property, the importer simply sees the value, whether that value is stored statically or is obtained by the trader invoking an operation on a dynamic property Dynamic properties have performance implications because they expose a trader to the implementation quality of objects outside the trader's control For example, if a trader invokes an operation on a dynamic property reference to get the current value but that operation is slow to complete, the entire matching process slows down High-quality implementations of the Trading Service take active steps to prevent complete lockup of the service if dynamic properties are slow to return the current value or are unavailable However, there is only so much a trader can do to protect itself against failure In addition, by their very nature, dynamic properties are slower to look up than static properties 1937 Proxy Offers A proxy offer is like a normal service offer in that it has a service type and contains properties that have values However, in addition, a proxy offer stores An object reference to a standardized Lookup interface A constraint recipe When an importer submits a constraint, the trader considers proxy offers as equivalent to ordinary offers during evaluation of the constraint If a proxy offer matches the constraint, the trader constructs a new constraint according to the constraint recipe The trader then invokes an operation on the Lookup interface stored with the proxy offer, passing the new constraint it has just constructed Eventually, the operation completes and returns a number of service offers to the trader, which adds them to the results returned to the importer
Code 39 Drawer In Visual Basic .NET
Using Barcode drawer for .NET Control to generate, create Code 39 Extended image in Visual Studio .NET applications.
EAN 128 Drawer In VS .NET
Using Barcode creator for ASP.NET Control to generate, create EAN / UCC - 13 image in ASP.NET applications.
Barcode Generator In Java
Using Barcode encoder for Java Control to generate, create barcode image in Java applications.
Scan Bar Code In Java
Using Barcode decoder for Java Control to read, scan read, scan image in Java applications.
Code128 Drawer In VS .NET
Using Barcode creator for Visual Studio .NET Control to generate, create Code128 image in Visual Studio .NET applications.
Generate GTIN - 13 In Visual Studio .NET
Using Barcode generator for .NET framework Control to generate, create EAN-13 image in VS .NET applications.
Bar Code Reader In VS .NET
Using Barcode scanner for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
Barcode Creator In .NET
Using Barcode generation for .NET Control to generate, create bar code image in .NET applications.
Code 128 Code Set C Reader In Visual Studio .NET
Using Barcode decoder for .NET Control to read, scan read, scan image in .NET framework applications.