这门课程所使用的教材是 Jia Zhang 老师自己编写的 Services Computing，课程内容其实相对老旧，不过我之前没有 Java 方面的经验，这门课还是让我学到了很多。

Week 1

1. Generations of Software Engineering:
   • 1st: Waterfall, compiler, OS, programming language;
   • 2nd: Stuffs we learned in FSE (OOAD, patterns, modeling…);
   • 3rd: SOC, platform is the key.
2. Service operational models:
   • Hosted service model;
   • Business process outsourcing;
   • Data-center outsourcing;
   • Services through online broker agency.
3. Service charge models:
   • Free-of-charge models;
   • Fee-based models;
   • Government service models.
4. Service Level Agreement (SLA): Pay more for better service. Can support large user base and usage scenarios.
5. A service-oriented system is modeled as a feedback system.
6. Service lifecycle:
   • Consulting & strategic plan;
   • Service engagement;
   • Service delivery;
   • Service operation;
   • Billing.
7. Vertical services: Service industries (banking, telecom, …); Horizontal services: Commom services (Business services: CRM, …, has business logic, supports multiple scenarios; IT services: database, OS).
8. SOC is a discipline (umbrella); SOA is a architectural model (overall software system design); Web service is the best enabling technology.
9. Typical service system: <Inputs, Outputs, Goals, Transformation, Components, Sensors>.
10. IT-enabled service: Outsourcing of processes that can be enabled with information technology and covers diverse areas; It’s about relationship between providers and consumers.

Week 2

1. HTML and XML are both based on SGML (Standard Generalized Markup Language).
2. XML tags are case-sensitive.
3. <![CDATA[This is a comment]]>.
4. Each XML document must have a unique first element: the root node.
5. DTD serves as the grammar for underlying XML document. Example:

<!DOCTYPE db[
    <!ELEMENT db(person*)>
    <!ELEMENT person(name, age, email)>
    <!ELEMENT name(#PCDATA)>
    <!ELEMENT age(#PCDATA)>
    <!ELEMENT email(#PCDATA)>
]>

1. XML Schema: Grammar for specifying valid XML documents. It is XML itself, so it’s verbose. Example:

<xs:element name="note">
    <xs:complexType>
        <xs:sequence>
            <xs:element name="to" type="xs:string" />
            <xs:element name="from" type="xs:string" />
            <xs:element name="heading" type="xs:string" />
            <xs:element name="body" type="xs:string" />
        </xs:sequence>
    </xs:complexType>
</xs:element>

1. DTD vs. XML Schema:
   • DTD (Old): Learning curve but terse;
   • XML Schema: Verbose but powerful (extensible, data types, namespaces).
2. XML parsing:
   • DOM (Document Object Model): Load whole XML document in memory: Faster;
   • SAX (Simple API for XML Parsing): Supports larger files.

3. XPath examples:

4. XQuery: For, Let, Where, Order by, Return (FLWOR). Example:

for $x in doc("book.xml")/bookstore/book
where $x/price > 30
order by $x/title
return $x/title

1. Other information:
   • JSON also has JSON Schema for validation;
   • Same Origin Policy (SOP): Full access to same origin (network, documents, storage, cookies);
   • XSLT (Extensible Stylesheet Language Transformations) is a language for transforming XML documents into other documents;
   • XML data binding refers to the process of representing the information in an XML document as an object in computer memory.

Week 3

1. REST (Representational State Transfer) is a server-side technique; AJAX is a web technique which can only retrieve data from the server side. AJAX can be part of REST but REST can never be AJAX.
2. HTTP (Hypertext Transfer Protocol).
3. Mashup:
   • Pros: lightweight app, lightweight & rapid development, low cost for gathering data;
   • Cons: Dependency, versioning, copyright, security.
   • Component discovery & selection -> Composition & immediate deployment -> Use and evolution -> … (loop).

Week 4

1. WSDL (Web Service Description Language). WSDL 1.1 example:

<message name="getPriceRequest">
    <part name="productId" type="xs:string" />
</message>

<message name="getPriceResponse">
    <part name="value" type="xs:string" />
</message>

<portType name="productPrice">
    <operation>
        <input message="getPriceRequest" />
        <output message="getPriceResponse" />
    </operation>
</portType>

1. SOAP (Single Object Access Protocol) acts as the messaging protocol binding to HTTP and SMTP:
   • WSDL binding to SOAP: In WSDL, you will need to specify binding with SOAP, then you can write SOAP message to communicate with the service.
2. BPEL (Business Process Execution Language):
   • WSDL / REST supports a stateless model; While a business process (BP) is characterized by long-running, stateful sequence of operations;
   • Business process orchestration;
   • BPEL also has <throw> and <catch>;
   • Example:
3. WSRF (Web Services Resource Framework) is stateful.
4. WS-I (Web Services Interoperability) organization is to tackle the challenges of interoperability among web services by introducing conventions and best practices.

Week 5

1. A web service can be published in a centralized services registry or a distributed services registry:
   • UDDI (Universal Description Discovery and Integration) registry is one typical example of centralized ~:
     • Four elements: BusinessEntity, BusinessService, BindingTemplate, tModel.
     • WSDL and UDDI:
     • UDDI Search Markup Language (USML) for supporting “Google” style services Search.
   • WSIL (Web Services Inspection Language) is one example of publishing web services as distributed documents. Example:
   • Advanced UDDI Search Engine (AUSE); Dynamic Service Discovery Framework (DSDF);
   • The federated framework provides a uniform interface for both UDDI-based and WSIL-based service discovery.

Week 7

1. LDA (Latent Dirichlet Allocation): Using Gibbs Sampling to calculate the result.

Week 10

1. MetaWSDL is a superset of WSDL:
   • It should be published to the Internet associated with the original WSDL documents.
2. ESB (Enterprise Service Bus) consists of 4 components: mediators, services registry, choreographer, rule engine. ESB can do:
   • Routing;
   • Message transformation: XML to object),
   • Message enhancement: Supply data included in original data;
   • Protocol transformation;
   • Service mapping;
   • Message processing;
   • Process choreography: Co-ordination of multiple business services, usually BPEL-based;
   • Services orchestration: Co-ordination of multiple implement services, usually BPEL-based;
   • Transaction management;
   • Security.
3. SOA Reference Architecture (SOA-RA) partitions an SOA-based system into reusable achitecture components.
4. Service-Oriented Modeling and Architecture (SOMA) guides a generic engineering process. It identifies 3 steps: identification, specification, realization.
5. Different layers of web service standards:
   • Transport Layer: HTTP / HTTPS, SMTP (Simple Mail Transport Protocol, on port 25), RMI (Java Remote Method Invocation) / IIOP (Internet Inter-ORB Protocol), JMS (Java Message Service);
   • Messaging Layer: XML, SOAP, WS-Adressing, WS-Renewable;
   • Description / Publishing / Discovery Layer: XSD (XML Schema Definition), WSDL, WSRF (WS-Resource Framework), WS-Resource Properties (part of WSRF), UDDI, Others (WS-Based Faults, WS-Policy, WS-Metadata Exchange);
   • QoS (Quality of Service Layer): WS-Security, WS-Policy, WS-TM (WS-Transaction Management), WS-Reliable Messaging, WS-Resource Lifetime;
   • Service Composition Layer: SOAP + WSDL + UDDI, BPEL4WS, WS-Service Group, WS-Notification
6. Industry-specific service-oriented standards:
   • Electronic Industry: RosettaNet.

Week 11

1. BPOL (Business Process Outsourcing Language).
2. SGA (Simple Genetic Algorithm) steps:
   • Select parents from population;
   • Shuffle mating pool;
   • For each pair, apply crossover with probability p_c;
   • For each offspring, apply mutation with probability p_m for each bit;
   • Replace old population with new offsprings.
3. Mutation-only-EA is possible, xover-only-EA won’t work.

Week 12

🍺

Week 13

1. RDF (Resource Description Framework):
   • It also has RDFS (RDF Schema): XMLS (XML Schema) is not an ontology language, while RDFS is an ontology language;
   • It is graphical formalism;
   • It supports containers: Bag, Seq, Alt.
2. In graph database, we have: Subject –Predicate–> Object; In RDF statement, we have: Resource –Property–>Value.
3. Relational Database has tables with pre-defined schema, while RDF has knowledge without constraints.
4. SPARQL (SPARQL Protocol and RDF Query Language):
   • SELECT, ASK (return a boolean), DESCRIBE, CONSTRUCT;
   • FILTER, DISTINCT, ORDER BY, LIMIT, OFFSET;
   • UNION (like “or”), OPTIONAL;
   • FROM, FROM NAMED.
5. Turtle (Terse RDF Triple Language). Turtle and SPARQL example:

Week 14

1. A more complex example of RDF:
2. OWL (Web Ontology Language); OWL-S (Semantic Markup for Web Service).
3. WSMF (Web Service Modeling Framework).

Week 15

1. A microservices architecture puts each element of functionality into a separate service. Modules run in different processes.

Key Information

Web Service Standard Stack

1. Transport layer: Provides core communication and interactions for web services.
   • HTTP / HTTPS: Runs on 80 / 443; Over TCP; Request / response protocol to transfer information over the Internet;
   • SMTP: Runs on 25; Simple Mail Transfer Protocol; Text-based protocol to send mail over the Internet;
   • RMI / IIOP: Java Romote Method Invocation to create distributed Java-based app; Internet Inter-ORB Protocol is a tranport protocol for communication under CORBA;
   • JMS (Java Message Service): A standard for reliable enterprise messaging.
2. Messaging layer: Appropriately formats messages for exchanging information between web services.
   • XML: “Common language” for services to exchange information;
   • SOAP: A simple, lightweight protocol to exchange structured and typed information;
   • WS-Adressing: Identifies WS endpoints, and to secure end-to-end identifications in messages;
   • WS-Renewable: provides a mechanism for renewing reference to web resource.
3. Description / Publishing / Discovery layer: No need to explain.
   • XSD: XML Schema Definition, no need to explain;
   • WSDL: No need to explain;
   • WS-Resource Property: Part of WSRF, describes how to view and modify web resourse;
   • UDDI: No need to explain;
   • WS-Base Faults: Defines an XML Schema type for base faults, and how they can be extended;
   • WS-Policy: Describe capabilities, requirements and general characteristics of a WS;
   • WS-Metadata Exchange: Facilitate the retrieval of metadata from WS.
4. QoS layer: Addresses the NFR of WS.
   • WS-Security: A set of mechanisms to secure SOAP message exchange;
   • WS-TM: “TM” for “Transaction Model”, protocols for managing transaction features in business activities;
   • WS-Resource Lifetime: To inspect and moniter the lifetime of WS and how WS can be destroyed;
5. Service Composition Layer: Allows developers to compose services together for a common business goal.
   • BPEL4WS: No need to explain;
   • WS-Service Group: A wide variety of collections of web services or WS-Resources;
   • WS-Notification: A set of specifications that provide support for events.