Upload
lexuyen
View
218
Download
4
Embed Size (px)
Citation preview
Dealing comfortably with the confusion of tongues
Ralf LämmelSoftware Languages Team, Koblenz
http://en.wikipedia.org/wiki/Tower_of_Babel_(M._C._Escher)
Consider the following system. How to reasonably
summarize its architecture?
RL: c9 is MSFT’s community-oriented
youtube.
Technology used in the 5th edition of Channel9
ASP.NET MVC
SparkView engine
jQuery
Silverlight 4
Windows Azure, SQL Azure, “other Azures”
ECN for the Content Delivery Network (videos)
http://channel9.msdn.com/Blogs/C9Team/Welcome-to-the-all-new-Channel-9
A b
egin
ner’s
vie
w o
n ...
Ch
an
ne
l9
http://www.epochtimes.de/pics/2009/07/20/xxl/2009-07-20-xxl--NASA_ueber_AP_Mond_Erde_1969_000_SAWH990715682240_new.jpg
Abstraction! Abstraction! Abstraction!
• What domain?
• Programming
• X/O/R mapping
• XML/database processing
• GUI
• ...
• What engineering?
• megamodeling programming
• software language engineering
CHO
OSE Forum
2012
Dom
ain-specific Engineering
A simpler riddle: how to usefully characterize these XML technologies?
DOM
SAX
StAX
DOM [Wikipedia]
The Document Object Model (DOM) is a cross-platform and language-independent convention for representing and interacting with objects in HTML, XHTML and XML documents. Aspects of the DOM (such as its "Elements") may be addressed and manipulated within the syntax of the programming language in use. The public interface of a DOM is specified in its Application Programming Interface (API). ...
SAX [Wikipedia]
SAX (Simple API for XML) is a sequential access parser API for XML. SAX provides a mechanism for reading data from an XML document. It is a popular alternative to the Document Object Model (DOM). ... A parser which implements SAX (ie, a SAX Parser) functions as a stream parser, with an event-driven API. The user defines a number of callback methods that will be called when events occur during parsing. ...
StAX [Wikipedia]
Streaming API for XML (StAX) is an application programming interface (API) to read and write XML documents, originating from the Java programming language community. Traditionally, XML APIs are either: tree based, ..., event based. ... These two access metaphors can be thought of as polar opposites. ...StAX was designed as a median between these two opposites. ...
DOM SAX StAX
Read (parse, query) XML • • •
Write XML • •
Metadata! Metadata! Metadata!
DOM SAX StAX
In-memory XML processing •Push-based XML parsing •Pull-based XML parsing •
Metadata! Metadata! Metadata!
DOM SAX StAX
Standardization • ·
.NET counterpart • •
Metadata! Metadata! Metadata!
Follow-up questions?
How to usefully abstract from XML in defining “push-based”?
How to usefully share conceptual understanding across DOM and JAXB?
... between JAXB and Hibernate?
...
An advanced programming class
The Expression Problem
The Visitor Design Pattern
Parsing
XML Processing
XML Validation
XML Data Binding
Database Access
O/R Mapping
Model View Controller
More Design Patterns
Reflection
Aspect-Oriented Programming
Functional OO Programming
Combinator Libraries
Generic Programming
Programming with Threads
Distributed Programming
WebService Programming
Our ultimate goal: heavily annotate programmig
and language technologies and their uses with metadata facilitating understanding.
A running example:
101companies
http://sourceforge.net/apps/mediawiki/developers/index.php?title=101companies
101companies
...
...
A few variation pointsX vs. O vs. R vs. λ etc.Static typing vs. dynamic typingTextual vs. abstract vs. visual syntaxGPPL vs. DSL vs. embedding vs. APIInstance- vs. operation-based mappingType checking vs. inference vs. reasoningCode first vs. schema first vs. mapping onlyIn-memory processing vs. push vs. pull parsingPure vs. impure transformations (or in between)Code vs. generative vs. model-driven vs. mapping
101 ways to run a company.
101companies
Modeling companies
Model ANTLRcompany : 'company' STRING '{' dept* '}'; dept : 'department' STRING '{' ('manager' employee) ('employee' employee)* dept* '}';employee : STRING '{' 'address' STRING 'salary' FLOAT '}';WS : (' '|'\r'? '\n'|'\t')+ {skip();};STRING : '"' (~'"')* '"';FLOAT : ('0'..'9')+ ('.' ('0'..'9')+)?;
CFGs for HR notation.The aspect of “sharing
knowledge” is underestimated.
Purity of CFGs is an i!usion.
Model Haske!
type Company = [Dept]data Dept = Dept Name Manager [SubUnit]type Manager = Employeedata Employee = Employee Name Address Salarydata SubUnit = PU Employee | DU Depttype Name = Stringtype Address = Stringtype Salary = Float
Structure is defined by sequence, cases, and
recursion.
Algebraic datatypes imply tree shape of
data instances.
Models use nominal & structural types,
and aliases.
Model Ecore
There are recurring themes for
primitive types.
Lists or co!ections may in fact be distinguished
structural forms.
Model Ecore/Java/EMF/** * @model */public interface Person extends EObject { /** * @model required="true" ordered="false" */ String getName(); void setName(String value); /** * @model required="true" ordered="false" */ String getAddress(); void setAddress(String value);}
Programs are
models.
Models are
programs.
<xs:element name="company"> ... </xs:element> <xs:complexType name="dept"> <xs:sequence> <xs:element name="name" type="xs:string"/> <xs:element name="manager" type="employee"/> <xs:element maxOccurs="unbounded" minOccurs="0" ref="subunit"/> </xs:sequence> </xs:complexType> <xs:element name="subunit"> <xs:complexType> <xs:choice> <xs:element name="pu" type="employee"/> <xs:element name="du" type="dept"/> </xs:choice> </xs:complexType> </xs:element> <xs:complexType name="employee"> <xs:sequence> <xs:element ref="person"/> <xs:element ref="salary"/> </xs:sequence> </xs:complexType> <xs:element name="person"> ... </xs:element> <xs:element name="salary"> ... </xs:element>
Model XSD
Let’s hope XSD goes away faster than
Cobol.
CREATE TABLE dept ( deptId INTEGER AUTO_INCREMENT PRIMARY KEY, name VARCHAR(100), managerId INTEGER, FOREIGN KEY (managerId) REFERENCES employee(employeeID), upperDeptId INTEGER, FOREIGN KEY (upperDeptId) REFERENCES dept(deptId) ON DELETE CASCADE ON UPDATE CASCADE);
CREATE TABLE employee (employeeId INTEGER AUTO_INCREMENT PRIMARY KEY,
name VARCHAR(50) NOT NULL, address VARCHAR(50) NOT NULL, salary DOUBLE, deptId INTEGER, FOREIGN KEY (deptId) REFERENCES dept(deptId) ON DELETE CASCADE ON UPDATE CASCADE);
Model SQL DDL
Type references may be represented through key references.
Eventua!y behavioral aspects
join in.
101companies
Totaling salaries
Total EMF/Java
public class Total {
public static double total(Company company) {
double total = 0;
for (Dept dept : company.getDepts())
total += total(dept);
return total;
}
private static double total(Dept dept) { ... }
private static double total(Subunit subunit) { ... }
private static double total(Employee employee) { ... }
}
Queries over (systems of)
recursive datatypes may require (systems of)
recursive “functions”.
Total Haske!
total :: Company -> Floattotal = everything (+) (mkQ 0 id)
Traversal or genera!y:quantification Type case
Total XML/XQuery
<result>{sum(//salary)}</result>
A domain-specific language for queries is good at doing, we!, queries.
Total XML/DOM/XPath
public static double total(Document doc) throws Exception { double total = 0; NodeList nodelist = XPathAPI.selectNodeList(doc, "//salary"); for (int i=0; i<nodelist.getLength(); i++) { Element elem = (Element)nodelist.item(i); total += Double.parseDouble(elem.getTextContent()); } return total;} Host language may run embedded programs
and inspect results.
Total XML/Java/JAXB
public class Total {
public static double total(Company c) {
double total = 0;
if (c.getDept() != null)
for (Dept d : c.getDept())
total += total(d);
return total;
}
public static double total(Dept d) { ... }
public static double total(Employee e) { ... }
public static double total(Subunit s) { ... }
}
POJOsTime and again.
Total SQL DML
SELECT SUM(salary) FROM employee;
What’s the XML/OO counterpart to projection?
Query languages provide aggregators.
Total Java / JDBC
public static double total(MyConnection myConnection) throws SQLException { double total = 0; String query = "SELECT salary FROM employee"; PreparedStatement pstmtEmployees = myConnection .getConn() .prepareStatement(query); ResultSet salaries = pstmtEmployees.executeQuery(); while (salaries.next()) total += salaries.getDouble("salary"); return total;}
Iterators on lazy server results
Total RDF/Java/Jena
public static double total(CompanyModel c) { double total = 0; StmtIterator i = c.getModel().listStatements( new SimpleSelector( null, c.SALARY, (RDFNode) null)); while (i.hasNext()) { Statement s = i.next(); total += s.getDouble(); } return total;}
Selection (quantification) over
graphs requires identities.
Ecore/ATLmodule Total;
create OUT: Total from IN: Company;
rule Company2Total {
from
company : Company!Company
to
t : Total!TotalWrapper (
total <- Company!Employee.allInstances()
-> collect(e | e.salary)
-> sum()
)
}
Total
Quantification,Projection,
A'regation
101companies
Cutting salaries
Cut Haske!
cut :: Company -> Company
cut = everywhere (mkT (/(2::Float)))
The type of a pure function reveals its nature of being a transformation.
Cut EMF/Java
public class Cut { public static void cutCompany(Company company) { for (Dept dept : company.getDepts()) cut(dept); } private static void cut(Dept dept) { ... } private static void cut(Subunit subunit) { ... } private static void cut(Employee employee) { employee.setSalary(employee.getSalary() / 2); }}
The appearance of “void” in an imperative (OO) language su'ests
impure transformation.
Cut XML/XQuery
copy $copy := .modify for $salary in $copy//salary return
replace value of node $salary with $salary div 2
return $copy
The distinction of pure vs. impure is not always easy.
Cut XML/XSLT
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:com="http://www.softlang.org/company.xsd" version="1.0"> <xsl:output method="xml" encoding="UTF-8"/> <xsl:template match="com:salary"> <xsl:copy> <xsl:value-of select=". div 2"/> </xsl:copy> </xsl:template> <xsl:template match="@*|node()"> <xsl:copy> <xsl:apply-templates select="@*|node()"/> </xsl:copy> </xsl:template></xsl:stylesheet> Don’t confuse notation with
concepts. Conceptua!y, XSLT is potentia!y simple.
Cut SQL DML
UPDATE employee SET salary = salary / 2;
Type-based quantification is rea!y simple with RDBMS.
Cut RDF/Java/Jena
public static void cut(CompanyModel c) { List<Statement> l = c.getModel().listStatements( new SimpleSelector( null, c.SALARY, (RDFNode) null)).toList(); for (Statement s : l) s.changeLiteralObject(s.getDouble() / 2);}
laziness + mutation = evil
Cut Ecore/ATL
module Cut;create OUT: Company from IN: Company;rule Company2Company { from s : Company!Company to t : Company!Company ( depts <- s.depts ) }rule Employee2Employee { from s : Company!Employee to t : Company!Employee ( person <- s.person, salary <- s.salary / 2 )}rule Dept2Dept { ... }rule Subunit2Subunit_Pu { ... }rule Subunit2Subunit_Du { ... }rule Person2Person { ... }
Rule-based thinking as opposed
to )ee-wheeling functions.
101companies
Mapping companies
Map Java/Serializable
import org.softlang.company.*;import java.io.FileInputStream;import java.io.ObjectInputStream;
FileInputStream fis = new FileInputStream("sampleCompany.ser");ObjectInputStream in = new ObjectInputStream(fis);Object o = in.readObject();in.close();Company c = (Company)o; Use a universal object
representation.
XML/Java/JAXBMap
@XmlAccessorType(XmlAccessType.FIELD)@XmlType(name = "", propOrder = {"name", "address"})@XmlRootElement(name = "person")public class Person { @XmlElement(required = true) protected String name; @XmlElement(required = true) protected String address; public String getName() { return name; } public void setName(String value) { name = value; } public String getAddress() { return address; } public void setAddress(String value) { address = value; }}
Annotations capture mapping including constraints.
XML/Java/JAXB
import org.softlang.company.*;import javax.xml.bind.JAXBContext;import javax.xml.bind.Unmarshaller;import java.io.File;
File input = new File("sampleCompany.xml");JAXBContext jaxbContext = JAXBContext.newInstance("org.softlang.company");Unmarshaller unMarshaller = jaxbContext.createUnmarshaller();Company c = (Company) unMarshaller.unmarshal(input);
Map
There is a 1:1 mapping between
names of program types & serialization-level names.
Ecore/Java/EMFMap
<GenModel ...> <genPackages prefix="Company" ...> <genClasses ecoreClass="Company.ecore#//Company"> <genFeatures ... ecoreFeature="...//Company/depts"/> </genClasses> <genClasses ecoreClass="Company.ecore#//Dept"> <genFeatures ... ecoreFeature="...//Dept/name"/> <genFeatures ... ecoreFeature="...//Dept/manager"/> <genFeatures ... ecoreFeature="...//Dept/subunits"/> </genClasses> ... </genPackages></GenModel>
types-to-types & properties-to-properties
mapping modulo renaming and exclusion.
Relational/Java/HibernateMap
<hibernate-mapping> <class name="org.softlang.om.Dept" table="DEPT"> <id name="id" column="DEPT_ID"> <generator class="native" /> </id> <property name="name" /> <many-to-one name="manager" class="org.softlang.om.Employee" column="MANAGER_ID" unique="true" /> <set name="subunits" table="DEPT_SUBUNIT" inverse="true"> <key column="DEPT_ID" /> <many-to-many column="SUBUNIT_ID" class="org.softlang.om.Subunit" /> </set> </class></hibernate-mapping>
Given: tables and classes. Recover relationship as
mapping.
Relational/Java/Hibernateimport org.hibernate.Session;import java.util.HashSet;import java.util.List;import java.util.Set;
Company c = new Company();c.session = new Configuration(). configure(). buildSessionFactory(). getCurrentSession(); c.session.beginTransaction();List<?> depts = c.session.createQuery( "from Dept where UPPER_DEPT_ID is null").list(); for (Object o : depts) c.getDepts().add((Dept) o);
Map
Persistence incl. transactions
Relational/Java/HibernateMap<hibernate-mapping> <class name="org.softlang.om.Dept" table="DEPT"> <id name="id" column="DEPT_ID"> <generator class="native" /> </id> <property name="name" /> <many-to-one name="manager" column="MANAGER_ID" class="org.softlang.om.Employee" /> <set name="employees" cascade="all"> <key column="DEPT_ID" /> <one-to-many class="org.softlang.om.Employee" /> </set> <set name="subDepartments" cascade="all"> <key column="UPPER_DEPT_ID" /> <one-to-many class="org.softlang.om.Dept" /> </set> </class></hibernate-mapping>
Another schema Another mapping
101companies
Interacting with companies
GUI Java/Swing
A GUI essentia!y provides a concrete syntax for the underlying language.
GUI Ajax/Java[Script] /GWT
Compared to a regular GUI, this scheme involves distribution, and, in
fact, mapping.
public CompanyInfo getCompanyInfo(Company company) { CompanyInfo companyInfo = new CompanyInfo(); for (Dept dept : company.getDepts()) companyInfo.getDeptsInfos().add(dept.getName()); return companyInfo;}
public class CompanyInfo implements Serializable { private List<String> deptsInfos; public CompanyInfo() { deptsInfos = new LinkedList<String>(); } public List<String> getDeptsInfos() { return deptsInfos; }}
public class Company { private List<Dept> depts; public Company() { depts = new LinkedList<Dept>(); } public List<Dept> getDepts() { return depts; } public Double total() { ... } public void cut() { ... }}
Ajax/Java[Script] /GWTMap
Instance-level mapping
Our ultimate goal: heavily annotate programmig
and language technologies and their uses with metadata facilitating understanding.
Thanks!Questions or comments?