tailieunhanh - Designing and Deploying RFID Applications Part 6

Tham khảo tài liệu 'designing and deploying rfid applications part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Advantages and New Applications of DHT-Based Discovery Services in EPCglobal Network 137 Fig. 5. Discovery Services architecture. DHTs have an important drawback with respect to LDAP while in LDAP the access control is already implemented by Access Control Lists ACLs in DHT fine grained controls have to be implemented. 4. DHT-based discovery services prototype The objective of the designed DS is to return a time-ordered list of links to multiple ECPIS instances which hold information related to a specific EPC. Therefore the DS is designed to create this list of links. The architecture of the full prototype has been divided into a set of logical components represented in Figure 5. Discovery services The DS implementation is composed by two components the DHT application and the Publish Query interface. DHT application The public methods insert and lookup of every DHT node in our implementation can be accessed by a remote application using Java RMI9 which is a Java API which performs the object-oriented equivalent of remote procedure calls RPC . The prototype of the previous methods is as follows public Boolean insert MessageDigest key String url and public String lookup MessageDigest key . The insert method has two parameters String url represents the URL of the EPCIS query interface with information about a specific EPC MessageDigest key represents the SHA1 hash Eastlake Jones 2001 of the related EPC. This method returns a Boolean which indicates if the insert operation has been properly finished. On the other hand 9 http javase technologies core basic rmi 138 Designing and Deploying RFID Applications the lookup method has a single parameter the SHA1 hash of an EPC and it returns an array with all the associated URLs. The insert method of the DHT node creates a content object with the key the URL and the its own nodehandle. After that it inserts the previous content in a message with the following fields the identifier of the origin