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Component-Based Engineering - Principles of Software Development - Lecture Notes, Study notes of Software Engineering

English and Foreign Languages University Software Engineering

Main points of this lecture are: Component-Based Engineering, Component Correctness, Component-Based Strategies, Service-Oriented Architecture, Kind of Access Control, Simple Object Access Protocol, Picture Changing, Guard Clauses, Xml Document

Typology: Study notes

2012/2013

Uploaded on 04/23/2013

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Formulate problem in terms of software

components with well-defined cohesive

properties.

Each software component is an

independent program.

Connect components via message-passing:

send requests and receive responses.

To the extent possible, construct a

situation in which correctness of

components implies correctness of the

total application.

Component-based engineering

Component-based Engineering

Monday, November 19, 2012

1:27 PM

Components Page 1

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Discover Study notes of Software Engineering English and Foreign Languages University

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Formulate problem in terms of software components with well-defined cohesive properties. Each software component is an independent program. Connect components via message-passing: send requests and receive responses. To the extent possible, construct a situation in which correctness of components implies correctness of the total application. Component-based engineering Component-based Engineering Monday, November 19, 2012 1:27 PM Docsity.com

Example: mashup Monday, November 19, 2012 4:38 PM Docsity.com

Components operate in an open world : any other process (on the internet(!)) can request services. (Subroutines operate in a closed world ; the source code of the current program completely defines how they are used) Thus, security (and integrity) become significant problems. Disadvantages of component-based engineering Disadvantages of component-based engineering Monday, November 19, 2012 1:42 PM Docsity.com

Designed for distributed network deployment... to optimize performance... No rule against running all services on the same machine. Service-Oriented Architecture (SOA): create "services" that perform parts of a computation. Designed to run on an individual Windows machine... To make writing an application easier... No rule against contacting components on other machines. Windows .NET: create "components" that interoperate to create an entire computation. Similar strengths and weaknesses. Similar architectures(!) Two component-centered strategies Two component-based strategies Monday, November 19, 2012 1:46 PM Docsity.com

Service request and response are XML documents. Clients convert subroutine calls to XML text. Basic security/integrity model: guard clauses based upon XPATH and Xschemas SOAP: Simple Object Access Protocol SOAP Monday, November 19, 2012 1:50 PM Docsity.com

Simple development

SOA

Wrote guard clauses into the code guard clauses are external, in a different language. The code functions in a closed world We have to guard against grevious input errors. How is the picture changing? Monday, November 19, 2012 4:50 PM Docsity.com

XPATH: a language for specifying parts of XML documents. Xschemas: a language for specifying the appropriate form for an XML document. Constructing SOAP Guard Clauses Constructing SOAP Guard Clauses Monday, November 19, 2012 1:55 PM Docsity.com

How SOAP guard clauses work Monday, November 19, 2012 1:57 PM Docsity.com

morris sylvester There is only one top level element. Element opens () and closes () must balance. This is a context- free grammar. Convention: = The basics of XML Xschema and XML concepts Monday, November 19, 2012 3:01 PM Docsity.com

Allow specification of parts of an XML document. ○ A node: one XML element. ○ A nodeset: a sequence of nodes. A condition: an empty nodeset is FALSE; a nodeset with at least one element is TRUE.

Can specify three kinds of things: An XPATH pattern that matches nothing is thought of as selecting the "empty nodeset".

The idea of XPATH Part 1: XPATH Monday, November 19, 2012 1:59 PM Docsity.com

cats/cat Docsity.com

foo/bar[@title='cat'] matches a tag inside a tag , that happens to have an attribute 'title' whose value is 'cat'

bar[@title and @publisher] matches a tag that has both 'title' and'publisher' attributes.

bar[what] matches a tag that contains a tag .

conditions : select locations that satisfy tests. ○ candy[name='chocolate'] ○ candy[name] ○ candy[2]
Examples: default is child : interpret names as children of current node.

○ self:: - current node. ○ parent:: - parent of current node. ○ preceding-sibling:: - siblings before current node. ○ following-sibling:: - siblings after current node. ○ descendant-or-self:: - current node or descendants.

axes : qualify how to interpret a name. ○ name[.='chocolate']/following-sibling::* ○ candy[name='chocolate']/following-sibling::candy
Examples: Advanced XPATH syntax Monday, November 19, 2012 2:06 PM Docsity.com

-. means self::node()

.. means parent::node()
// means /descendant-or-self::node()/
foo/bar is the same as foo/child::bar
foo//bar is the same as foo/descendant-or-self::bar.
@thing is the same as attribute::thing.
foo[] is a foo that contains . XPATH shorthands: Monday, November 19, 2012 2:05 PM Docsity.com

[...] - apply a condition to a pattern.
child::[2] - second child of context node. child::[@name and @address] - children with name and address attributes.

Example: preceding-sibling::[position()= 1] (or preceding-sibling::[1]) matches the node before the current one. Preceding indices count up as one moves backward.

Example: following-sibling::[position()= 1] (or following-sibling::[1]) matches the node following the current one at the same level.

Example: child::[count(@)=2]: matches all children with exactly two attributes!

Functions in conditions Monday, November 19, 2012 2:04 PM Docsity.com

Component-Based Engineering - Principles of Software Development - Lecture Notes, Study notes of Software Engineering

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SOA